{"id":1909,"date":"2026-07-31T20:22:49","date_gmt":"2026-07-31T12:22:49","guid":{"rendered":"https:\/\/jutrion.com\/?p=1909"},"modified":"2026-07-31T20:32:37","modified_gmt":"2026-07-31T12:32:37","slug":"dinh-co-bo-chuyen-mach-tu-dong","status":"publish","type":"post","link":"https:\/\/jutrion.com\/vi\/automatic-transfer-switch-sizing\/","title":{"rendered":"T\u00f4i c\u1ea7n C\u00f4ng t\u1eafc chuy\u1ec3n ngu\u1ed3n t\u1ef1 \u0111\u1ed9ng c\u1ee1 n\u00e0o? \u0110\u1ecbnh m\u1ee9c kW sang Ampe c\u1ee7a m\u00e1y ph\u00e1t \u0111i\u1ec7n, \u0111\u1ecbnh c\u1ee1 3 pha v\u00e0 l\u1ef1a ch\u1ecdn c\u1ef1c"},"content":{"rendered":"<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"341\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/automatic-transfer-switch-sizing-diagram-1024x341.png\" alt=\"\" class=\"wp-image-1912\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/automatic-transfer-switch-sizing-diagram-1024x341.png 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/automatic-transfer-switch-sizing-diagram-300x100.png 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/automatic-transfer-switch-sizing-diagram-768x256.png 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/automatic-transfer-switch-sizing-diagram.png 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\">S\u01a1 \u0111\u1ed3 \u0111\u1ecbnh c\u1ee1 c\u00f4ng t\u1eafc chuy\u1ec3n m\u1ea1ch t\u1ef1 \u0111\u1ed9ng cho th\u1ea5y ngu\u1ed3n \u0111i\u1ec7n l\u01b0\u1edbi v\u00e0 m\u00e1y ph\u00e1t c\u1ea5p cho t\u1ea3i quan tr\u1ecdng qua ATS JUTRION.<\/figcaption><\/figure>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-1\">Tr\u1ea3 l\u1eddi nhanh: B\u1ea1n c\u1ea7n c\u00f4ng t\u1eafc chuy\u1ec3n m\u1ea1ch t\u1ef1 \u0111\u1ed9ng c\u1ee1 n\u00e0o?<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f4ng t\u1eafc chuy\u1ec3n m\u1ea1ch t\u1ef1 \u0111\u1ed9ng ph\u1ea3i ch\u1ecbu \u0111\u01b0\u1ee3c d\u00f2ng \u0111i\u1ec7n cao nh\u1ea5t c\u00f3 th\u1ec3 \u0111i qua n\u00f3 t\u1eeb m\u1ed9t trong hai ngu\u1ed3n. H\u00e3y t\u00ednh d\u00f2ng \u0111i\u1ec7n \u0111\u00f3 t\u1eeb t\u1ea3i \u0111\u01b0\u1ee3c chuy\u1ec3n m\u1ea1ch, kh\u00f4ng ch\u1ec9 t\u1eeb nh\u00e3n m\u00e1y ph\u00e1t, sau \u0111\u00f3 ch\u1ecdn \u0111\u1ecbnh m\u1ee9c ATS ph\u00f9 h\u1ee3p ti\u1ebfp theo. Tr\u01b0\u1edbc khi \u0111\u1eb7t h\u00e0ng, c\u0169ng c\u1ea7n x\u00e1c nh\u1eadn \u0111i\u1ec7n \u00e1p, pha, s\u1ed1 c\u1ef1c, chuy\u1ec3n m\u1ea1ch trung t\u00ednh, kh\u1ea3 n\u0103ng ch\u1ecbu ng\u1eafn m\u1ea1ch, ph\u01b0\u01a1ng th\u1ee9c chuy\u1ec3n ti\u1ebfp, ch\u1ee9c n\u0103ng b\u1ed9 \u0111i\u1ec1u khi\u1ec3n v\u00e0 ti\u00eau chu\u1ea9n \u00e1p d\u1ee5ng.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">M\u00e1y ph\u00e1t 100 kVA kh\u00f4ng t\u1ef1 \u0111\u1ed9ng y\u00eau c\u1ea7u c\u00f4ng t\u1eafc chuy\u1ec3n m\u1ea1ch 100 A. \u1ede \u0111i\u1ec7n \u00e1p 400 V ba pha, 100 kVA t\u01b0\u01a1ng \u1ee9ng v\u1edbi kho\u1ea3ng 144 A. \u1ede \u0111i\u1ec7n \u00e1p 230 V m\u1ed9t pha, c\u00f9ng c\u00f4ng su\u1ea5t bi\u1ec3u ki\u1ebfn \u0111\u00f3 s\u1ebd t\u01b0\u01a1ng \u1ee9ng v\u1edbi kho\u1ea3ng 435 A. Con s\u1ed1 c\u00f4ng su\u1ea5t gi\u1eef nguy\u00ean. D\u00f2ng \u0111i\u1ec7n th\u00ec kh\u00f4ng.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u00f3 l\u00e0 l\u00fd do vi\u1ec7c \u0111\u1ecbnh c\u1ee1 c\u00f4ng t\u1eafc chuy\u1ec3n m\u1ea1ch t\u1ef1 \u0111\u1ed9ng b\u1eaft \u0111\u1ea7u t\u1eeb s\u01a1 \u0111\u1ed3 m\u1ed9t s\u1ee3i v\u00e0 t\u1ea3i \u0111\u01b0\u1ee3c chuy\u1ec3n m\u1ea1ch. \u0110\u1ecbnh m\u1ee9c m\u00e1y ph\u00e1t ch\u1ec9 l\u00e0 m\u1ed9t \u0111\u1ea7u v\u00e0o. N\u00f3 kh\u00f4ng ph\u1ea3i l\u00e0 to\u00e0n b\u1ed9 c\u00e2u tr\u1ea3 l\u1eddi.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-2\">Tr\u01b0\u1edbc ti\u00ean h\u00e3y x\u00e1c \u0111\u1ecbnh ATS s\u1ebd th\u1ef1c s\u1ef1 mang t\u1ea3i g\u00ec<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">Tr\u01b0\u1edbc khi d\u00f9ng c\u00f4ng th\u1ee9c, h\u00e3y v\u1ebd ranh gi\u1edbi quanh ph\u00eda t\u1ea3i c\u1ee7a ATS. \u0110i\u1ec1u n\u00e0y tr\u00e1nh l\u1ed7i \u0111\u1ecbnh c\u1ee1 ph\u1ed5 bi\u1ebfn nh\u1ea5t: t\u00ednh to\u00e1n m\u1ed9t ph\u1ea7n c\u1ee7a h\u1ec7 th\u1ed1ng trong khi ch\u1ec9 \u0111\u1ecbnh c\u00f4ng t\u1eafc cho ph\u1ea7n kh\u00e1c.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">ATS c\u00f3 th\u1ec3 chuy\u1ec3n m\u1ea1ch:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>to\u00e0n b\u1ed9 d\u1ecbch v\u1ee5 h\u1ea1 th\u1ebf ho\u1eb7c t\u1ee7 ph\u00e2n ph\u1ed1i ch\u00ednh;<\/li>\n\n\n\n<li>thanh c\u00e1i kh\u1ea9n c\u1ea5p ho\u1eb7c an to\u00e0n t\u00ednh m\u1ea1ng chuy\u00ean d\u1ee5ng;<\/li>\n\n\n\n<li>b\u1ea3ng ph\u1ee5 t\u1ea3i ch\u1ecdn l\u1ecdc c\u1ea5p cho m\u00e1y b\u01a1m, chi\u1ebfu s\u00e1ng, \u0111i\u1ec1u khi\u1ec3n, l\u00e0m l\u1ea1nh ho\u1eb7c thi\u1ebft b\u1ecb CNTT;<\/li>\n\n\n\n<li>m\u1ed9t m\u00e1y ho\u1eb7c quy tr\u00ecnh c\u00f4ng nghi\u1ec7p;<\/li>\n\n\n\n<li>\u0111\u1ea7u ra c\u1ee7a m\u00e1y ph\u00e1t, b\u1ed9 bi\u1ebfn t\u1ea7n ho\u1eb7c ngu\u1ed3n \u0111i\u1ec7n l\u01b0\u1edbi th\u1ee9 hai.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Gi\u1ea3 s\u1eed m\u1ed9t t\u00f2a nh\u00e0 c\u00f3 d\u1ecbch v\u1ee5 ch\u00ednh 800 A nh\u01b0ng ch\u1ec9 c\u00f3 b\u1ea3ng t\u1ea3i thi\u1ebft y\u1ebfu 250 A \u0111\u01b0\u1ee3c d\u1ef1 ph\u00f2ng. ATS l\u1eafp tr\u00ean b\u1ea3ng thi\u1ebft y\u1ebfu \u0111\u00f3 kh\u00f4ng t\u1ef1 \u0111\u1ed9ng l\u00e0 thi\u1ebft b\u1ecb 800 A. Y\u00eau c\u1ea7u d\u00f2ng \u0111i\u1ec7n li\u00ean t\u1ee5c c\u1ee7a n\u00f3 theo m\u1ea1ch \u0111\u01b0\u1ee3c chuy\u1ec3n m\u1ea1ch, tu\u00e2n theo c\u00e1c quy t\u1eafc thi\u1ebft k\u1ebf chi ph\u1ed1i v\u00e0 b\u1ed1 tr\u00ed thi\u1ebft b\u1ecb b\u1ea3o v\u1ec7.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">V\u1ea5n \u0111\u1ec1 ng\u01b0\u1ee3c l\u1ea1i c\u0169ng x\u1ea3y ra. M\u00e1y ph\u00e1t c\u00f3 th\u1ec3 nh\u1ecf h\u01a1n d\u1ecbch v\u1ee5 \u0111i\u1ec7n l\u01b0\u1edbi, nh\u01b0ng ATS v\u1eabn n\u1eb1m tr\u00ean \u0111\u01b0\u1eddng ngu\u1ed3n b\u00ecnh th\u01b0\u1eddng v\u00e0 li\u00ean t\u1ee5c mang t\u1ea3i \u0111\u00e3 ch\u1ecdn khi c\u00f3 \u0111i\u1ec7n l\u01b0\u1edbi. C\u00f3 th\u1ec3 c\u1ea7n c\u1eaft t\u1ea3i ho\u1eb7c b\u1ea3ng t\u1ea3i thi\u1ebft y\u1ebfu n\u1ebfu m\u00e1y ph\u00e1t kh\u00f4ng th\u1ec3 c\u1ea5p cho m\u1ecdi th\u1ee9 k\u1ebft n\u1ed1i ph\u00eda h\u1ea1 l\u01b0u. C\u00f4ng t\u1eafc kh\u00f4ng th\u1ec3 l\u00e0m cho m\u00e1y ph\u00e1t qu\u00e1 nh\u1ecf mang th\u00eam t\u1ea3i.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote has-small-font-size is-layout-flow wp-block-quote-is-layout-flow\">\n<h3 class=\"wp-block-heading has-medium-font-size\">L\u1eadp b\u1ea3ng \u0111\u1ea7u v\u00e0o \u0111\u1ecbnh c\u1ee1 tr\u01b0\u1edbc khi b\u1ea1n t\u00ednh to\u00e1n<\/h3>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u1ecbnh c\u1ee1 ATS t\u1ed1t b\u1eaft \u0111\u1ea7u b\u1eb1ng m\u1ed9t danh s\u00e1ch ng\u1eafn c\u00e1c \u0111\u1ea7u v\u00e0o \u0111\u00e3 \u0111\u01b0\u1ee3c x\u00e1c minh. N\u1ebfu m\u1ed9t s\u1ed1 m\u1ee5c ch\u01b0a bi\u1ebft, h\u00e3y \u0111\u00e1nh d\u1ea5u ch\u00fang l\u00e0 \u0111i\u1ec3m m\u1edf thay v\u00ec che gi\u1ea5u sau h\u1ec7 s\u1ed1 an to\u00e0n l\u1edbn. Vi\u1ec7c t\u0103ng khung ampe kh\u00f4ng th\u1ec3 s\u1eeda \u0111\u01b0\u1ee3c b\u1ed1 tr\u00ed trung t\u00ednh kh\u00f4ng ph\u00f9 h\u1ee3p, \u0111\u1ecbnh m\u1ee9c ch\u1ecbu s\u1ef1 c\u1ed1 th\u1ea5p ho\u1eb7c b\u1ed9 \u0111i\u1ec1u khi\u1ec3n kh\u00f4ng th\u1ec3 giao ti\u1ebfp v\u1edbi m\u00e1y ph\u00e1t.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u0110\u1ea7u v\u00e0o<\/th><th>T\u1ea1i sao n\u00f3 quan tr\u1ecdng<\/th><th>N\u01a1i x\u00e1c minh<\/th><\/tr><\/thead><tbody><tr><td>T\u1ea3i \u0111\u01b0\u1ee3c chuy\u1ec3n m\u1ea1ch<\/td><td>X\u00e1c \u0111\u1ecbnh d\u00f2ng \u0111i\u1ec7n m\u00e0 ATS ph\u1ea3i mang<\/td><td>B\u1ea3ng t\u1ea3i, s\u01a1 \u0111\u1ed3 m\u1ed9t s\u1ee3i, nhu c\u1ea7u \u0111o \u0111\u01b0\u1ee3c<\/td><\/tr><tr><td>Ngu\u1ed3n b\u00ecnh th\u01b0\u1eddng v\u00e0 ngu\u1ed3n thay th\u1ebf<\/td><td>X\u00e1c \u0111\u1ecbnh b\u1ed1 tr\u00ed ngu\u1ed3n v\u00e0 tr\u00ecnh t\u1ef1 b\u1ed9 \u0111i\u1ec1u khi\u1ec3n<\/td><td>S\u01a1 \u0111\u1ed3 m\u1ed9t s\u1ee3i v\u00e0 d\u1eef li\u1ec7u m\u00e1y ph\u00e1t\/b\u1ed9 bi\u1ebfn t\u1ea7n<\/td><\/tr><tr><td>\u0110i\u1ec7n \u00e1p v\u00e0 t\u1ea7n s\u1ed1<\/td><td>\u0110\u1eb7t y\u00eau c\u1ea7u c\u00e1ch \u0111i\u1ec7n, c\u1ea3m bi\u1ebfn v\u00e0 b\u1ed9 \u0111i\u1ec1u khi\u1ec3n<\/td><td>Th\u00f4ng s\u1ed1 k\u1ef9 thu\u1eadt d\u1ef1 \u00e1n v\u00e0 nh\u00e3n ngu\u1ed3n<\/td><\/tr><tr><td>H\u1ec7 th\u1ed1ng m\u1ed9t pha ho\u1eb7c ba pha<\/td><td>Thay \u0111\u1ed5i c\u00f4ng th\u1ee9c d\u00f2ng \u0111i\u1ec7n v\u00e0 c\u1ea5u h\u00ecnh c\u1ef1c<\/td><td>B\u1ea3n v\u1ebd ph\u00e2n ph\u1ed1i<\/td><\/tr><tr><td>C\u00f4ng su\u1ea5t t\u00ednh b\u1eb1ng A, kW ho\u1eb7c kVA<\/td><td>X\u00e1c \u0111\u1ecbnh ph\u01b0\u01a1ng ph\u00e1p t\u00ednh to\u00e1n n\u00e0o h\u1ee3p l\u1ec7<\/td><td>Danh s\u00e1ch t\u1ea3i, d\u1eef li\u1ec7u m\u00e1y ph\u00e1t, nh\u00e3n thi\u1ebft b\u1ecb<\/td><\/tr><tr><td>H\u1ec7 s\u1ed1 c\u00f4ng su\u1ea5t v\u00e0 hi\u1ec7u su\u1ea5t<\/td><td>C\u1ea7n thi\u1ebft khi chuy\u1ec3n \u0111\u1ed5i m\u1ed9t s\u1ed1 gi\u00e1 tr\u1ecb kW sang d\u00f2ng \u0111i\u1ec7n<\/td><td>D\u1eef li\u1ec7u thi\u1ebft b\u1ecb ho\u1eb7c m\u00e1y ph\u00e1t<\/td><\/tr><tr><td>T\u1ea3i \u0111\u1ed9ng c\u01a1 v\u00e0 m\u00e1y bi\u1ebfn \u00e1p<\/td><td>\u1ea2nh h\u01b0\u1edfng \u0111\u1ebfn tr\u00ecnh t\u1ef1 chuy\u1ec3n m\u1ea1ch, d\u00f2ng kh\u1edfi \u0111\u1ed9ng v\u00e0 ph\u1ea3n \u1ee9ng ngu\u1ed3n<\/td><td>Danh s\u00e1ch \u0111\u1ed9ng c\u01a1 v\u00e0 nghi\u00ean c\u1ee9u kh\u1edfi \u0111\u1ed9ng<\/td><\/tr><tr><td>D\u00f2ng s\u1ef1 c\u1ed1 kh\u1ea3 d\u1ee5ng<\/td><td>\u0110\u1eb7t ra kh\u1ea3 n\u0103ng ch\u1ecbu \u0111\u1ef1ng v\u00e0 \u0111\u00f3ng c\u1eaft y\u00eau c\u1ea7u<\/td><td>Nghi\u00ean c\u1ee9u ng\u1eafn m\u1ea1ch<\/td><\/tr><tr><td>Thi\u1ebft k\u1ebf n\u1ed1i \u0111\u1ea5t v\u00e0 trung t\u00ednh<\/td><td>X\u00e1c \u0111\u1ecbnh xem trung t\u00ednh li\u1ec1n hay trung t\u00ednh chuy\u1ec3n m\u1ea1ch l\u00e0 ph\u00f9 h\u1ee3p<\/td><td>Nghi\u00ean c\u1ee9u n\u1ed1i \u0111\u1ea5t v\u00e0 quy t\u1eafc l\u1eafp \u0111\u1eb7t \u0111\u1ecba ph\u01b0\u01a1ng<\/td><\/tr><tr><td>M\u00f4i tr\u01b0\u1eddng xung quanh v\u00e0 v\u1ecf t\u1ee7<\/td><td>C\u00f3 th\u1ec3 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn \u0111\u1ed9 t\u0103ng nhi\u1ec7t, gi\u1ea3m c\u00f4ng su\u1ea5t v\u00e0 d\u00f2ng s\u1ea3n ph\u1ea9m<\/td><td>D\u1eef li\u1ec7u hi\u1ec7n tr\u01b0\u1eddng v\u00e0 h\u01b0\u1edbng d\u1eabn c\u1ee7a nh\u00e0 s\u1ea3n xu\u1ea5t<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">For an existing facility, measured demand can be more useful than adding every connected nameplate. A plant may have 600 kW of connected equipment but never operate all of it simultaneously. Conversely, a short measurement taken during a light production shift may understate the real maximum. Use a representative demand record, the operating schedule, and planned expansion together.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a new facility, the load schedule should identify which loads are continuous, intermittent, mutually exclusive, or shed during generator operation. This is the point where electrical design and operational priorities meet. The ATS should serve the intended emergency system, not an imaginary condition in which every connected device runs at full load forever.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-3\">Convert the Available Project Data into Amps<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">Use current directly when a verified maximum design current is already available. If the project gives power in kW or kVA, convert it using the correct system voltage and phase arrangement.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">When the Input Is kVA<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Apparent power in kVA already includes the effect of power factor, so do not divide by power factor a second time.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Single-phase:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = S \u00d7 1,000 \/ V<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Three-phase:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = S \u00d7 1,000 \/ (\u221a3 \u00d7 V<sub>LL<\/sub>)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Here,&nbsp;<strong>I<\/strong>&nbsp;is line current in amperes,&nbsp;<strong>S<\/strong>&nbsp;is apparent power in kVA,&nbsp;<strong>V<\/strong>&nbsp;is single-phase voltage, and&nbsp;<strong>V<sub>LL<\/sub><\/strong>&nbsp;is three-phase line-to-line voltage.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">When the Input Is kW<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Real power requires a power-factor assumption. If the kW figure is mechanical output from a motor rather than electrical input, efficiency also matters.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Single-phase electrical load:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = P \u00d7 1,000 \/ (V \u00d7 PF)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Three-phase electrical load:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = P \u00d7 1,000 \/ (\u221a3 \u00d7 V<sub>LL<\/sub>&nbsp;\u00d7 PF)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a motor specified by shaft-output kW, divide by efficiency as well. Use nameplate current where possible because it reflects the actual motor design better than a generic efficiency estimate.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Available input<\/th><th>What to use<\/th><th>Common mistake<\/th><\/tr><\/thead><tbody><tr><td>Verified load current in A<\/td><td>Use the design current directly<\/td><td>Converting it back to power and adding new assumptions<\/td><\/tr><tr><td>Generator or load rating in kVA<\/td><td>Use the kVA formula for the correct phase and voltage<\/td><td>Dividing by power factor twice<\/td><\/tr><tr><td>Electrical load in kW<\/td><td>Use voltage, phase, and a justified power factor<\/td><td>Assuming PF = 1 for a mixed commercial or industrial load<\/td><\/tr><tr><td>Motor output in kW<\/td><td>Prefer nameplate current; otherwise include PF and efficiency<\/td><td>Treating mechanical output as electrical input<\/td><\/tr><tr><td>Main breaker rating only<\/td><td>Check whether the ATS carries the full service or a selected-load feeder<\/td><td>Automatically copying the main-breaker frame onto every ATS<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Connected Load, Maximum Demand, and Source Capacity<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">These three values can be different, and each answers a different question.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Connected load<\/strong>&nbsp;is the sum of equipment that could be connected. It is useful for understanding the system but can overstate simultaneous current when loads operate at different times.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Maximum demand<\/strong>&nbsp;is the highest credible simultaneous load under the defined operating condition. This is often the most relevant starting point for the ATS continuous-current requirement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Source capacity<\/strong>&nbsp;is what the utility, generator, transformer, inverter, or battery system can deliver. The alternate source may be deliberately smaller than the connected load when priority controls shed nonessential circuits.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Consider a hotel with 420 A of connected emergency-side equipment. The operating study shows that fire pumps, evacuation lighting, security, and selected elevators create a maximum transferred demand of 285 A. The generator is rated for 350 A, and the controls prevent comfort HVAC from connecting during an outage. A 400 A ATS may be a defensible starting point. Adding all 420 A without recognizing the control sequence could push the project into a larger, more expensive frame. Using only the 350 A generator rating would miss the reason the system works.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The load-management sequence must be reliable and documented. If the controls fail and all 420 A can connect, the smaller source may be overloaded even though the ATS itself can carry the current. ATS sizing and generator sizing are connected, but they are not the same calculation.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color wp-elements-4\">Three Worked ATS Sizing Examples<\/h2>\n<\/blockquote>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Example 1: A Single-Phase Essential-Load Panel<\/h3>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">Consider an illustrative small commercial site with a 230 V single-phase essential-load panel. The calculated simultaneous load is 11.5 kVA.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = 11.5 \u00d7 1,000 \/ 230 = 50 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The calculated current is 50 A. The correct purchasing decision is not simply \u201cbuy a 50 A ATS.\u201d Check the continuous loading expected by the installation rules, the available product ratings, cable and protective-device ratings, and any planned load growth. If the verified requirement exceeds 50 A after those checks, a 63 A frame may be the practical selection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A compact&nbsp;<a href=\"https:\/\/jutrion.com\/vi\/ats\/\">JUTRION automatic transfer switch<\/a>&nbsp;may suit this type of selected-load application, but the exact model still has to match the source voltage, pole arrangement, controller logic, and short-circuit conditions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Example 2: A 100 kVA, 400 V Three-Phase Generator<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"341\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/100-kva-400v-three-phase-ats-sizing-1024x341.png\" alt=\"\" class=\"wp-image-1910\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/100-kva-400v-three-phase-ats-sizing-1024x341.png 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/100-kva-400v-three-phase-ats-sizing-300x100.png 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/100-kva-400v-three-phase-ats-sizing-768x256.png 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/100-kva-400v-three-phase-ats-sizing.png 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><strong>T\u00ednh to\u00e1n k\u00edch th\u01b0\u1edbc ATS ba pha cho m\u00e1y ph\u00e1t 100 kVA 400 V cho k\u1ebft qu\u1ea3 kho\u1ea3ng 144 A.<\/strong><\/code><\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A commercial building uses a 100 kVA standby generator at 400 V, three-phase. The ATS transfers a dedicated emergency board that the generator is intended to supply.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I = 100 \u00d7 1,000 \/ (\u221a3 \u00d7 400)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>I \u2248 144 A<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A 125 A ATS would be too small for the generator&#8217;s rated apparent-power output. The next suitable standard rating could be 160 A, provided the transferred-load calculation, operating duty, product data, and installation rules support it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Now change one assumption. If the emergency board&#8217;s verified maximum demand is only 105 A and load management prevents additional circuits from connecting during generator operation, the engineer may size around that controlled load rather than the theoretical output of the generator. That decision must be documented in the system design. A supplier should not infer it from the generator nameplate.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This case also shows why an ATS can be rated higher than the generator. A 160 A switch connected to a source capable of 144 A is not inherently a mismatch. The switch rating is a carrying limit, not a command that forces 160 A from the generator.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Should the ATS Match the Generator or the Main Breaker?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">There is no universal \u201cmatch the larger nameplate\u201d rule. Follow the current path.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the ATS is installed at a full-service transfer point, it may carry the normal-source service load whenever the utility is available. The generator can still be smaller if the system has approved load management, but the transfer equipment and distribution architecture must suit the full normal path.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the ATS feeds a separate essential-load board, its rating can follow that feeder&#8217;s calculated demand and design rules rather than the building&#8217;s main service rating. This is common when only critical circuits require backup power.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the ATS is packaged with a generator for one dedicated machine, the generator current, machine demand, starting behavior, and feeder protection may all be close. Even then, verify the voltage, phase, fault current, and controller interface instead of selecting by kVA alone.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>ATS location<\/th><th>Primary sizing basis<\/th><th>Important secondary check<\/th><\/tr><\/thead><tbody><tr><td>Full-service transfer<\/td><td>Maximum current through the service path<\/td><td>Service rules, generator load management, fault current<\/td><\/tr><tr><td>Essential-load subpanel<\/td><td>Calculated demand of selected circuits<\/td><td>Feeder protection and load-shedding logic<\/td><\/tr><tr><td>Dedicated machine or process<\/td><td>Machine operating current<\/td><td>Starting duty and acceptable interruption<\/td><\/tr><tr><td>Generator output switch<\/td><td>Generator rated current and connected transferred load<\/td><td>Overload protection and future parallel\/source plans<\/td><\/tr><tr><td>Utility-to-utility transfer<\/td><td>Load current carried from either utility source<\/td><td>Source independence and transition permission<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A larger ATS can be used with a smaller generator when the electrical ratings and protection are coordinated. A smaller ATS cannot be justified merely because the generator is smaller if the switch carries a higher utility-side load during normal operation.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Example 3: A Motor-Heavy Industrial Emergency Bus<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">An industrial emergency bus has 180 A of running load, including pumps and ventilation motors. Selecting a 200 A ATS may appear sufficient. The harder question is what happens during transfer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Motor loads can retain voltage after disconnection. If a second source is connected while the residual voltage is out of phase, the electrical and mechanical stress can exceed normal running conditions. Generator voltage and frequency may also dip when several motors restart together.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Do not solve this by applying a universal \u201cmotor load \u00d7 1.5\u201d rule. That shortcut mixes three different decisions:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>the continuous current the ATS contacts must carry;<\/li>\n\n\n\n<li>the making and utilization duty of the switching equipment;<\/li>\n\n\n\n<li>the generator&#8217;s ability to accept starting kVA and voltage dip.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">A better design may use staged restarting, load shedding, a delayed-transition neutral position, or in-phase transfer. A neutral delay can allow residual voltage from inductive loads to decay before the alternate source is connected. The chosen ATS and controller must support the required sequence.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For this project, the ampere frame cannot be finalized until the motor-starting study, transfer sequence, generator response, and upstream protection are reviewed. The honest preliminary answer is \u201cat least the verified continuous-load requirement, then confirm the transfer duty.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-large-font-size\">How Load Type Changes the Decision After the Amp Calculation<\/h2>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">Two projects can have the same 250 A running current and need different transfer solutions. The difference lies in what the load does when voltage disappears and returns.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Resistive Heating and Lighting<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Predominantly resistive loads usually have a straightforward relationship between power and current. The main questions are simultaneity, continuous duty, and source capacity. Some lighting systems, however, include electronic drivers with high inrush or harmonic current, so the label \u201clighting\u201d is not enough.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Motors, Pumps, Compressors, and Fans<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Motors create starting kVA, residual voltage, and possible phase-angle stress during transfer. The system may restart motors sequentially rather than all at once. A delayed transition can provide time for residual voltage to decay, while in-phase transfer controls can wait for a suitable phase relationship. The correct approach depends on the process and equipment.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Transformers<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Transformer energization can produce a high magnetizing inrush that varies with residual flux and the point on the voltage waveform at closing. A transfer that is acceptable for steady-state transformer current may still cause a severe source voltage dip or nuisance operation of protection. Review the transformer and generator study rather than applying a generic current margin.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">UPS, Data-Center, and Electronic Loads<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electronic loads can be sensitive to interruption time and source quality. They may also draw nonlinear current. A UPS can bridge an open-transition gap, but the generator and ATS controller must allow the alternate source to stabilize. Transfer thresholds that are too narrow can cause repeated switching when generator voltage or frequency hunts near the acceptance limit.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Fire Pumps and Life-Safety Loads<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">These systems are governed by application-specific rules and project requirements. They are not ordinary motor feeders. The current IEC 60947-6-1:2026 edition includes specific provisions for transfer switching equipment used with electric-driven fire-pump control equipment. Treat the complete approved system, controller, source, and installation rules together.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color wp-elements-5\">Select the Next Suitable ATS Rating, Not the Nearest Number<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">Once the design current is established, compare it with available product ratings. Never round down. Also avoid oversizing without a reason. A much larger ATS may increase enclosure size, cable-termination requirements, panel cost, and spare-parts burden without improving system performance.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Calculated current<\/th><th>Possible next frame<\/th><th>What must still be checked<\/th><\/tr><\/thead><tbody><tr><td>28 A<\/td><td>32 A or the next offered rating<\/td><td>Continuous duty, conductor and protective-device coordination<\/td><\/tr><tr><td>50 A<\/td><td>63 A where required by the verified design basis<\/td><td>Load growth, terminals, enclosure, pole configuration<\/td><\/tr><tr><td>144 A<\/td><td>160 A<\/td><td>Actual transferred load, source capacity, fault rating<\/td><\/tr><tr><td>365 A<\/td><td>400 A<\/td><td>Temperature, bus\/cable arrangement, transfer duty<\/td><\/tr><tr><td>1,420 A<\/td><td>1,600 A<\/td><td>High-current switch architecture, protection, maintenance strategy<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These are illustrative mappings, not a substitute for a model-specific catalogue. JUTRION offers ATS solutions across a broad current range, but availability, class, poles, controller, and test ratings vary by series.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-6\">Check Rated Operational Current and Utilization Category<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The number printed as a frame or thermal-current rating is not always the current the device can switch under every load condition. For an IEC project, verify the model&#8217;s rated operational current,&nbsp;<strong>Ie<\/strong>, at the project voltage and for the applicable utilization category.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">IEC transfer switching equipment may be marked with categories such as AC-31, AC-32, or AC-33. The category reflects the type of load and switching duty used to establish the rating. Motor and mixed inductive loads can impose a more demanding making and breaking duty than predominantly resistive loads. A product that carries its full frame current in one category may have a lower Ie in another.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This changes the selection sequence. If the calculation gives 365 A, a nominal 400 A frame is only a candidate. The relevant data table must also show an Ie of at least 365 A at the system voltage and required utilization category. If it does not, move to a larger frame or a product designed for that duty.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Result from the calculation<\/th><th>Preliminary frame<\/th><th>Next decisive check<\/th><\/tr><\/thead><tbody><tr><td>50 A at 230 V single-phase<\/td><td>63 A candidate<\/td><td>Ie at 230 V, load duty, poles, and continuous operating condition<\/td><\/tr><tr><td>144 A at 400 V three-phase<\/td><td>160 A candidate<\/td><td>Ie at 400\/415 V for the required utilization category<\/td><\/tr><tr><td>365 A motor-heavy load<\/td><td>400 A candidate<\/td><td>AC-33 duty, restart sequence, generator response, and product data<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">This is the missing bridge between a power-system calculation and a real catalogue selection. The formula produces a required current. The manufacturer&#8217;s tested Ie confirms whether a particular model can perform that duty.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-7\">Check Temperature, Enclosure, Terminals, and Installation Duty<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Catalogue current is tied to stated conditions. A switch installed in a cool, ventilated electrical room does not experience the same thermal environment as a sealed outdoor cabinet exposed to sun, dust, salt, or high ambient temperature.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Confirm the permitted ambient range and any manufacturer derating. Do not assume that choosing the next frame automatically guarantees full current at an elevated temperature. Enclosure construction, ventilation, busbar arrangement, cable size, number of conductors per terminal, and internal heat from adjacent equipment all affect the final assembly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Terminal capacity deserves early attention on high-current projects. A 1,600 A ATS may require multiple parallel cables or bus connections per phase. The panel builder needs the approved conductor range, lug arrangement, bending space, entry direction, torque values, and neutral capacity. An electrically adequate switch that cannot accept the specified cables is not a usable selection.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Frequency of operation also matters. An ATS used only during occasional utility outages has a different operating profile from a generator-to-generator remote site that alternates sources on a schedule. Mechanical and electrical endurance data, maintenance access, spare parts, and bypass requirements become more important as transfer frequency and the cost of downtime increase.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-8\">Ampere Rating Is Only the First Gate<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">A correctly calculated current can still lead to the wrong ATS. Complete the following checks before issuing a purchase specification.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">1. Match Both Sources for Voltage, Phase, and Frequency<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The ATS and its controller must be suitable for the normal source, alternate source, and load. Confirm nominal voltage, allowable sensing range, single-phase or three-phase arrangement, phase sequence, and frequency. For a generator source, confirm the controller does not transfer until voltage and frequency are stable.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">2. Decide Whether the Neutral Must Be Switched<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A three-phase, three-pole ATS switches the phase conductors and normally leaves a solid neutral. A four-pole ATS switches the neutral as a fully rated pole. Switched-neutral arrangements are commonly considered with separately derived sources, but \u201cuse 4P for every generator\u201d is not a safe universal rule.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The decision depends on the grounding and bonding design, source arrangement, residual-current protection, local rules, and how neutral current paths behave in normal and emergency operation. Have the system designer confirm this point. It cannot be settled by the ampere formula.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">3. Choose the Transfer Equipment Class and Protection Architecture<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A PC-class transfer switch is primarily a transfer device. It generally relies on coordinated upstream overcurrent protection. A CB-class arrangement uses circuit-breaker-based switching devices and may integrate overload and short-circuit interruption functions, depending on the tested assembly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Do not select the class from speed or price alone. Ask who is responsible for clearing a downstream fault, which protective device is upstream, and whether the complete combination has the required ratings. JUTRION&#8217;s&nbsp;<a href=\"https:\/\/jutrion.com\/vi\/mccb\/\">MCCB range<\/a>&nbsp;and high-current&nbsp;<a href=\"https:\/\/jutrion.com\/vi\/high-current-power-protection-acb-guide\/\">ACB system guide<\/a>&nbsp;provide useful context for the protective side of that decision.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">4. Check IEC Short-Circuit Ratings or UL WCR<\/h3>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"341\" src=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/ats-rated-current-vs-short-circuit-rating-1024x341.png\" alt=\"\" class=\"wp-image-1911\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/ats-rated-current-vs-short-circuit-rating-1024x341.png 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/ats-rated-current-vs-short-circuit-rating-300x100.png 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/ats-rated-current-vs-short-circuit-rating-768x256.png 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/07\/ats-rated-current-vs-short-circuit-rating.png 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><strong>So s\u00e1nh d\u00f2ng \u0111i\u1ec7n v\u1eadn h\u00e0nh \u0111\u1ecbnh m\u1ee9c Ie c\u1ee7a ATS v\u1edbi c\u00e1c th\u00f4ng s\u1ed1 ng\u1eafn m\u1ea1ch Icw, Icm v\u00e0 \u0111\u1ecbnh m\u1ee9c c\u00f3 \u0111i\u1ec1u ki\u1ec7n.<\/strong><\/code><\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">A 400 A current rating tells you how much load current the ATS can carry under its rated conditions. It does not tell you that the switch can survive a 50 kA fault at its installation point.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For an IEC project, review the short-circuit values marked for the transfer switching equipment. Depending on the product and protection arrangement, these can include rated short-time withstand current&nbsp;<strong>Icw<\/strong>, rated short-circuit making capacity&nbsp;<strong>Icm<\/strong>, or a conditional short-circuit rating tied to a specified upstream protective device. The time value and protection conditions matter as much as the current value.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a North American application, the withstand and closing rating&nbsp;<strong>WCR<\/strong>&nbsp;must be adequate for the available fault current at the ATS location under its marked conditions. A WCR can depend on a particular fuse or circuit breaker and its clearing time.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In either system, use the model-specific coordination information. The breaking capacity printed on an upstream MCCB cannot simply be copied into the ATS specification; the two devices perform different jobs during a fault.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">5. Select the Transition Method Around the Load<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Open transition is break-before-make: the first source disconnects before the second connects. Delayed transition adds an intentional off interval. Closed transition briefly parallels acceptable sources and introduces additional controls and utility requirements.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Most applications do not choose a transition method by current rating. They choose it by load behavior, interruption tolerance, residual voltage, generator response, and source-paralleling rules.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">6. Specify the Controller and Project Interfaces<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A utility-to-generator system normally needs more than voltage sensing. Check generator start and stop contacts, start delay, source-available settings, transfer delay, retransfer delay, cool-down time, manual operation, test functions, alarm contacts, and remote indication.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Industrial and critical-power projects may also need RS485\/Modbus communication, event logging, load shedding, fire-system interfaces, or a bypass-isolation arrangement. These features can change the series and enclosure even when the ampere rating stays the same.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color wp-elements-9\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Use This Nine-Step Automatic Transfer Switch Sizing Process<\/h2>\n<\/blockquote>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Mark the ATS boundary on the one-line diagram.<\/strong>\u00a0Identify every circuit that remains downstream in normal and emergency operation.<\/li>\n\n\n\n<li><strong>Establish the maximum credible transferred demand.<\/strong>\u00a0Use measured data or a documented load schedule, not an unexplained sum or a light-load snapshot.<\/li>\n\n\n\n<li><strong>Convert power to current correctly.<\/strong>\u00a0Distinguish amperes, kW, and kVA; use the correct single- or three-phase formula.<\/li>\n\n\n\n<li><strong>Check the alternate source.<\/strong>\u00a0Confirm that the generator, inverter, or second utility source can supply the intended load and starting sequence.<\/li>\n\n\n\n<li><strong>Select the next suitable current rating.<\/strong>\u00a0Use the verified design basis and available product frames. Never round down.<\/li>\n\n\n\n<li><strong>Review load behavior during transfer.<\/strong>\u00a0Address motor residual voltage, transformer inrush, UPS ride-through, load shedding, and restart order.<\/li>\n\n\n\n<li><strong>Complete the electrical configuration.<\/strong>\u00a0Specify voltage, frequency, poles, neutral treatment, PC\/CB architecture, and transition method.<\/li>\n\n\n\n<li><strong>Verify fault and protection coordination.<\/strong>\u00a0Compare the marked withstand\/closing performance with available fault current and the upstream protective device.<\/li>\n\n\n\n<li><strong>Finish the project specification.<\/strong>\u00a0Add controller functions, communications, enclosure, terminals, ambient conditions, applicable standard, quantity, and destination market.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">This sequence intentionally separates calculation from verification. It lets a buyer obtain a fast preliminary size without pretending that the result alone authorizes installation.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Keep the calculation record with the quotation. At minimum, record the source of the load data, the date or operating condition represented by any measurements, the diversity assumptions, the formula used, and the reason for choosing the final frame. If a later project revision adds a pump, changes the generator voltage, or moves the ATS to a different point on the one-line diagram, the team can see immediately whether the original result is still valid. Without that record, a frame size often survives through several drawing revisions even after the assumptions behind it have changed.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-10\">IEC 60947-6-1:2026 and UL 1008 Are Not Interchangeable Labels<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The current IEC edition is&nbsp;<a href=\"https:\/\/webstore.iec.ch\/en\/publication\/90494\" target=\"_blank\" rel=\"noopener\">IEC 60947-6-1:2026<\/a>. It applies to transfer switching equipment used to transfer loads between power sources up to 1,000 V AC or 1,500 V DC. The 2026 edition covers manually, remotely, and automatically operated equipment and adds specific treatment for areas including bypass\/isolation equipment, closed-transition ATSE, standalone ATS controllers, and fire-pump transfer switching equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For North American projects,&nbsp;<a href=\"https:\/\/www.ul.com\/services\/switch-certification-and-evaluation-services\" target=\"_blank\" rel=\"noopener\">UL Solutions identifies UL 1008<\/a>&nbsp;as the standard used for automatic transfer switches in emergency and optional standby systems, as well as nonautomatic transfer switches. Installation requirements also depend on the applicable electrical code, project classification, and authority having jurisdiction.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">An ampere calculation is useful in either market. It does not prove that a specific ATS is certified, listed, or approved for that project. Confirm the exact model, standard, voltage, short-circuit rating, and installation conditions before ordering.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-11\">Why Two ATS Units with the Same Amp Rating May Not Be Equivalent<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"has-palette-color-6-background-color has-background wp-block-paragraph\">The ampere rating is only one line on the nameplate. Two 400 A transfer switches may carry the same normal load current while using different switching mechanisms, neutral arrangements, protection architectures, controllers, and short-circuit ratings.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Five checks reveal most of the meaningful differences:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Transfer architecture:<\/strong>\u00a0A PC-class device normally depends on coordinated upstream protection, while a CB-class design uses circuit-breaker-based switching and may include overcurrent functions.<\/li>\n\n\n\n<li><strong>Number of poles:<\/strong>\u00a0A three-pole unit normally retains a solid neutral. A four-pole unit switches the neutral and must suit the grounding design.<\/li>\n\n\n\n<li><strong>Fault performance:<\/strong>\u00a0The marked short-circuit withstand and closing capability must match the available fault current and the specified upstream protective device.<\/li>\n\n\n\n<li><strong>Controller functions:<\/strong>\u00a0Source sensing, generator contacts, adjustable delays, event records, communication, and load-control functions vary widely.<\/li>\n\n\n\n<li><strong>Applicable evidence:<\/strong>\u00a0Voltage, utilization duty, ambient conditions, IEC or UL requirements, and model-specific test documentation must match the project.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">These are system differences, not optional sales extras. A basic PC-class ATS may be the correct answer for a coordinated distribution panel. A critical facility may need delayed transition, advanced monitoring, or bypass isolation. Neither product is automatically better because it has more functions. The correct device is the one whose tested configuration matches the one-line diagram and operating sequence.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-12\">Record the Result as a Complete Preliminary Specification<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">After the calculation, write down the assumptions and the remaining checks. A preliminary specification should identify the transferred load, calculated current, proposed frame, voltage, phase, frequency, source arrangement, poles, transition method, protection architecture, controller interfaces, installation environment, and applicable standard.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This record makes the engineering review easier and prevents a frame size from being separated from the assumptions behind it. It also creates a clean handoff between the system designer, panel builder, generator supplier, and ATS manufacturer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Once those inputs are confirmed, compare them with the available configurations in the&nbsp;<a href=\"https:\/\/jutrion.com\/vi\/ats\/\">JUTRION automatic transfer switch range<\/a>. Final model selection should be based on the model-specific ratings and project conditions, not on current alone.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The practical order is simple: define what the ATS will carry, calculate the current, verify Ie for the actual utilization category, and then complete the pole, transition, controller, and short-circuit checks.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" style=\"font-size:clamp(16.293px, 1.018rem + ((1vw - 3.2px) * 0.68), 25px);\">Technical References<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/90494\" target=\"_blank\" rel=\"noopener\">IEC 60947-6-1:2026 \u2014 Transfer switching equipment<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.ul.com\/services\/switch-certification-and-evaluation-services\" target=\"_blank\" rel=\"noopener\">UL Solutions \u2014 Switch certification and evaluation services<\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>Quick Answer: What Size Automatic Transfer Switch Do You Need? An automatic transfer switch must carry the highest current that can pass through it from either source. Calculate that current from the transferred load, not from the generator label alone, then select the next suitable ATS rating. Before ordering, also confirm voltage, phase, poles, neutral [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":1913,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1909","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-electrical-guides"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/posts\/1909","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/comments?post=1909"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/posts\/1909\/revisions"}],"predecessor-version":[{"id":1914,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/posts\/1909\/revisions\/1914"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/media\/1913"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/media?parent=1909"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/categories?post=1909"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jutrion.com\/vi\/wp-json\/wp\/v2\/tags?post=1909"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}