{"id":2209,"date":"2026-10-08T22:36:04","date_gmt":"2026-10-08T14:36:04","guid":{"rendered":"https:\/\/jutrion.com\/?p=2209"},"modified":"2026-10-08T22:36:07","modified_gmt":"2026-10-08T14:36:07","slug":"275v-vs-320v-vs-385v-spd-choose-correct-uc","status":"publish","type":"post","link":"https:\/\/jutrion.com\/th\/275v-vs-320v-vs-385v-spd-choose-correct-uc\/","title":{"rendered":"275 V \u0e40\u0e17\u0e35\u0e22\u0e1a\u0e01\u0e31\u0e1a 320 V \u0e40\u0e17\u0e35\u0e22\u0e1a\u0e01\u0e31\u0e1a 385 V SPD: \u0e27\u0e34\u0e18\u0e35\u0e01\u0e32\u0e23\u0e40\u0e25\u0e37\u0e2d\u0e01 Uc \u0e17\u0e35\u0e48\u0e16\u0e39\u0e01\u0e15\u0e49\u0e2d\u0e07"},"content":{"rendered":"<h2 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-large-font-size wp-elements-1\">275 V, 320 V \u0e2b\u0e23\u0e37\u0e2d 385 V: \u0e04\u0e33\u0e15\u0e2d\u0e1a\u0e2a\u0e31\u0e49\u0e19 \u0e46<\/h2>\n\n\n\n<p 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\u0e04\u0e37\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14\u0e17\u0e35\u0e48\u0e44\u0e14\u0e49\u0e23\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e2d\u0e19\u0e38\u0e21\u0e31\u0e15\u0e34\u0e0b\u0e36\u0e48\u0e07\u0e22\u0e31\u0e07\u0e04\u0e07\u0e2d\u0e22\u0e39\u0e48\u0e40\u0e2b\u0e19\u0e37\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14\u0e17\u0e35\u0e48 SPD \u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e1b\u0e23\u0e30\u0e2a\u0e1a\u0e44\u0e14\u0e49\u0e2d\u0e22\u0e48\u0e32\u0e07\u0e15\u0e48\u0e2d\u0e40\u0e19\u0e37\u0e48\u0e2d\u0e07\u0e43\u0e19\u0e42\u0e2b\u0e21\u0e14\u0e17\u0e35\u0e48\u0e40\u0e0a\u0e37\u0e48\u0e2d\u0e21\u0e15\u0e48\u0e2d \u0e21\u0e31\u0e19\u0e15\u0e49\u0e2d\u0e07\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e17\u0e19\u0e15\u0e48\u0e2d\u0e2a\u0e20\u0e32\u0e27\u0e30\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e0a\u0e31\u0e48\u0e27\u0e04\u0e23\u0e32\u0e27\u0e17\u0e35\u0e48\u0e04\u0e32\u0e14\u0e2b\u0e27\u0e31\u0e07\u0e43\u0e19\u0e08\u0e38\u0e14\u0e19\u0e31\u0e49\u0e19\u0e44\u0e14\u0e49 \u0e2b\u0e25\u0e31\u0e07\u0e08\u0e32\u0e01\u0e40\u0e25\u0e37\u0e2d\u0e01 U<sub>c<\/sub>, \u0e15\u0e23\u0e27\u0e08\u0e2a\u0e2d\u0e1a\u0e27\u0e48\u0e32\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e23\u0e30\u0e14\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19\u0e17\u0e35\u0e48\u0e44\u0e14\u0e49 U<sub>p<\/sub> \u0e22\u0e31\u0e07\u0e04\u0e07\u0e15\u0e48\u0e33\u0e1e\u0e2d\u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a\u0e2d\u0e38\u0e1b\u0e01\u0e23\u0e13\u0e4c\u0e17\u0e35\u0e48\u0e44\u0e14\u0e49\u0e23\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e01\u0e32\u0e23\u0e15\u0e23\u0e27\u0e08\u0e2a\u0e2d\u0e1a\u0e04\u0e23\u0e31\u0e49\u0e07\u0e2a\u0e38\u0e14\u0e17\u0e49\u0e32\u0e22\u0e19\u0e35\u0e49\u0e21\u0e35\u0e04\u0e27\u0e32\u0e21\u0e2a\u0e33\u0e04\u0e31\u0e0d\u0e40\u0e1e\u0e23\u0e32\u0e30 U<sub>c<\/sub> \u0e44\u0e21\u0e48\u0e43\u0e0a\u0e48\u0e01\u0e32\u0e23\u0e08\u0e31\u0e14\u0e2d\u0e31\u0e19\u0e14\u0e31\u0e1a\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e40\u0e01\u0e34\u0e19 A 385 V cartridge \u0e44\u0e21\u0e48\u0e43\u0e0a\u0e48\u0e40\u0e27\u0e2d\u0e23\u0e4c\u0e0a\u0e31\u0e19\u0e17\u0e35\u0e48\u0e41\u0e02\u0e47\u0e07\u0e41\u0e01\u0e23\u0e48\u0e07\u0e01\u0e27\u0e48\u0e32\u0e02\u0e2d\u0e07 275 V cartridge \u0e43\u0e19\u0e17\u0e38\u0e01\u0e14\u0e49\u0e32\u0e19 \u0e21\u0e31\u0e19\u0e2d\u0e32\u0e08\u0e17\u0e19\u0e15\u0e48\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e04\u0e27\u0e32\u0e21\u0e16\u0e35\u0e48\u0e1e\u0e25\u0e31\u0e07\u0e07\u0e32\u0e19\u0e17\u0e35\u0e48\u0e2a\u0e39\u0e07\u0e02\u0e36\u0e49\u0e19 \u0e41\u0e15\u0e48\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e40\u0e23\u0e34\u0e48\u0e21\u0e08\u0e33\u0e01\u0e31\u0e14\u0e17\u0e35\u0e48\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e17\u0e35\u0e48\u0e2a\u0e39\u0e07\u0e02\u0e36\u0e49\u0e19\u0e41\u0e25\u0e30\u0e2d\u0e32\u0e08\u0e21\u0e35 U \u0e17\u0e35\u0e48\u0e1b\u0e23\u0e30\u0e01\u0e32\u0e28\u0e2a\u0e39\u0e07\u0e01\u0e27\u0e48\u0e32<sub>p<\/sub>. \u0e14\u0e31\u0e07\u0e19\u0e31\u0e49\u0e19\u0e01\u0e32\u0e23\u0e40\u0e25\u0e37\u0e2d\u0e01\u0e17\u0e35\u0e48\u0e14\u0e35\u0e17\u0e35\u0e48\u0e2a\u0e38\u0e14\u0e08\u0e36\u0e07\u0e15\u0e49\u0e2d\u0e07\u0e21\u0e35\u0e04\u0e27\u0e32\u0e21\u0e2a\u0e21\u0e14\u0e38\u0e25\u0e23\u0e30\u0e2b\u0e27\u0e48\u0e32\u0e07\u0e04\u0e27\u0e32\u0e21\u0e40\u0e2a\u0e16\u0e35\u0e22\u0e23\u0e43\u0e19\u0e01\u0e32\u0e23\u0e1a\u0e23\u0e34\u0e01\u0e32\u0e23\u0e01\u0e31\u0e1a\u0e23\u0e30\u0e14\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19.<\/p>\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\/10\/01-spd-uc-275v-320v-385v-comparison-1024x341.webp\" alt=\"\" class=\"wp-image-2231\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/01-spd-uc-275v-320v-385v-comparison-1024x341.webp 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/01-spd-uc-275v-320v-385v-comparison-300x100.webp 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/01-spd-uc-275v-320v-385v-comparison-768x256.webp 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/01-spd-uc-275v-320v-385v-comparison-18x6.webp 18w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/01-spd-uc-275v-320v-385v-comparison.webp 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><em>\u0e01\u0e32\u0e23\u0e40\u0e1b\u0e23\u0e35\u0e22\u0e1a\u0e40\u0e17\u0e35\u0e22\u0e1a\u0e01\u0e32\u0e23\u0e08\u0e31\u0e14\u0e2d\u0e31\u0e19\u0e14\u0e31\u0e1a Uc \u0e02\u0e2d\u0e07 SPD 275 V, 320 V \u0e41\u0e25\u0e30 385 V \u0e1a\u0e19\u0e27\u0e07\u0e08\u0e23 230 V \u0e23\u0e30\u0e2b\u0e27\u0e48\u0e32\u0e07\u0e2a\u0e32\u0e22\u0e01\u0e31\u0e1a\u0e01\u0e25\u0e32\u0e07<\/em><\/code><\/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-2\">U<sub>c<\/sub> \u0e2b\u0e21\u0e32\u0e22\u0e16\u0e36\u0e07\u0e2d\u0e30\u0e44\u0e23\u0e43\u0e19 SPD AC<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">U<sub>c<\/sub> \u0e04\u0e37\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e17\u0e33\u0e07\u0e32\u0e19\u0e15\u0e48\u0e2d\u0e40\u0e19\u0e37\u0e48\u0e2d\u0e07\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14\u0e17\u0e35\u0e48\u0e2d\u0e32\u0e08\u0e16\u0e39\u0e01\u0e19\u0e33\u0e44\u0e1b\u0e43\u0e0a\u0e49\u0e02\u0e49\u0e32\u0e21\u0e02\u0e31\u0e49\u0e27 SPD \u0e20\u0e32\u0e22\u0e43\u0e15\u0e49\u0e40\u0e07\u0e37\u0e48\u0e2d\u0e19\u0e44\u0e02\u0e17\u0e35\u0e48\u0e23\u0e30\u0e1a\u0e38\u0e42\u0e14\u0e22\u0e1c\u0e39\u0e49\u0e1c\u0e25\u0e34\u0e15 \u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a\u0e1c\u0e25\u0e34\u0e15\u0e20\u0e31\u0e13\u0e11\u0e4c AC \u0e21\u0e31\u0e19\u0e21\u0e31\u0e01\u0e08\u0e30\u0e40\u0e1b\u0e47\u0e19\u0e04\u0e48\u0e32\u0e23\u0e32\u0e01\u0e17\u0e35\u0e48\u0e2a\u0e2d\u0e07\u0e17\u0e35\u0e48\u0e04\u0e27\u0e32\u0e21\u0e16\u0e35\u0e48\u0e17\u0e35\u0e48\u0e1b\u0e23\u0e30\u0e01\u0e32\u0e28 \u0e43\u0e19\u0e23\u0e30\u0e2b\u0e27\u0e48\u0e32\u0e07\u0e01\u0e32\u0e23\u0e17\u0e33\u0e07\u0e32\u0e19\u0e1b\u0e01\u0e15\u0e34 SPD \u0e15\u0e49\u0e2d\u0e07\u0e22\u0e31\u0e07\u0e04\u0e07\u0e40\u0e2a\u0e16\u0e35\u0e22\u0e23\u0e17\u0e35\u0e48\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e19\u0e35\u0e49\u0e42\u0e14\u0e22\u0e44\u0e21\u0e48\u0e17\u0e33\u0e15\u0e31\u0e27\u0e40\u0e2b\u0e21\u0e37\u0e2d\u0e19\u0e27\u0e48\u0e32\u0e41\u0e15\u0e48\u0e25\u0e30\u0e22\u0e2d\u0e14\u0e02\u0e2d\u0e07\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e2b\u0e25\u0e31\u0e01\u0e40\u0e1b\u0e47\u0e19\u0e01\u0e32\u0e23\u0e01\u0e23\u0e30\u0e0a\u0e32\u0e01.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e04\u0e33\u0e08\u0e33\u0e01\u0e31\u0e14\u0e04\u0e27\u0e32\u0e21\u0e19\u0e35\u0e49\u0e2d\u0e18\u0e34\u0e1a\u0e32\u0e22\u0e27\u0e48\u0e32\u0e17\u0e33\u0e44\u0e21 U<sub>c<\/sub> \u0e15\u0e49\u0e2d\u0e07\u0e2d\u0e48\u0e32\u0e19\u0e02\u0e49\u0e32\u0e21\u0e42\u0e2b\u0e21\u0e14\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19\u0e40\u0e09\u0e1e\u0e32\u0e30\u0e2b\u0e19\u0e36\u0e48\u0e07\u0e42\u0e2b\u0e21\u0e14:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>L\u2013N:<\/strong> \u0e40\u0e1f\u0e2a\u0e01\u0e31\u0e1a\u0e01\u0e25\u0e32\u0e07;<\/li>\n\n\n\n<li><strong>L\u2013PE:<\/strong> \u0e40\u0e1f\u0e2a\u0e01\u0e31\u0e1a\u0e14\u0e34\u0e19\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19;<\/li>\n\n\n\n<li><strong>N\u2013PE:<\/strong> \u0e01\u0e25\u0e32\u0e07\u0e01\u0e31\u0e1a\u0e14\u0e34\u0e19\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19; \u0e2b\u0e23\u0e37\u0e2d<\/li>\n\n\n\n<li><strong>L\u2013L:<\/strong> \u0e40\u0e1f\u0e2a\u0e01\u0e31\u0e1a\u0e40\u0e1f\u0e2a\u0e43\u0e19\u0e01\u0e32\u0e23\u0e08\u0e31\u0e14\u0e40\u0e23\u0e35\u0e22\u0e07\u0e17\u0e35\u0e48\u0e2d\u0e2d\u0e01\u0e41\u0e1a\u0e1a\u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a\u0e42\u0e2b\u0e21\u0e14\u0e19\u0e31\u0e49\u0e19.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e40\u0e04\u0e23\u0e37\u0e2d\u0e02\u0e48\u0e32\u0e22\u0e2a\u0e32\u0e21\u0e40\u0e1f\u0e2a\u0e2d\u0e32\u0e08\u0e16\u0e39\u0e01\u0e2d\u0e18\u0e34\u0e1a\u0e32\u0e22\u0e27\u0e48\u0e32\u0e40\u0e1b\u0e47\u0e19 230\/400 V \u0e41\u0e15\u0e48\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e02\u0e49\u0e32\u0e21\u0e42\u0e21\u0e14\u0e39\u0e25 SPD \u0e41\u0e15\u0e48\u0e25\u0e30\u0e15\u0e31\u0e27\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e40\u0e1b\u0e47\u0e19 230 V \u0e2b\u0e23\u0e37\u0e2d 400 V \u0e02\u0e36\u0e49\u0e19\u0e2d\u0e22\u0e39\u0e48\u0e01\u0e31\u0e1a\u0e27\u0e48\u0e32\u0e42\u0e21\u0e14\u0e39\u0e25\u0e19\u0e31\u0e49\u0e19\u0e40\u0e0a\u0e37\u0e48\u0e2d\u0e21\u0e15\u0e48\u0e2d\u0e17\u0e35\u0e48\u0e44\u0e2b\u0e19 \u0e1b\u0e49\u0e32\u0e22\u0e23\u0e30\u0e1a\u0e1a\u0e41\u0e25\u0e30\u0e1b\u0e49\u0e32\u0e22 cartridge \u0e08\u0e36\u0e07\u0e44\u0e21\u0e48\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e43\u0e0a\u0e49\u0e41\u0e17\u0e19\u0e01\u0e31\u0e19\u0e44\u0e14\u0e49.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e2d\u0e22\u0e48\u0e32\u0e2a\u0e31\u0e1a\u0e2a\u0e19 U<sub>c<\/sub> \u0e01\u0e31\u0e1a\u0e15\u0e31\u0e27\u0e40\u0e25\u0e02\u0e2d\u0e37\u0e48\u0e19 \u0e46 \u0e17\u0e35\u0e48\u0e1e\u0e34\u0e21\u0e1e\u0e4c\u0e1a\u0e19 SPD:<\/p>\n\n\n\n<figure class=\"wp-block-table jutrion-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u0e01\u0e32\u0e23\u0e17\u0e33\u0e40\u0e04\u0e23\u0e37\u0e48\u0e2d\u0e07\u0e2b\u0e21\u0e32\u0e22<\/th><th>\u0e2a\u0e34\u0e48\u0e07\u0e17\u0e35\u0e48\u0e21\u0e31\u0e19\u0e2d\u0e18\u0e34\u0e1a\u0e32\u0e22<\/th><th>\u0e2a\u0e34\u0e48\u0e07\u0e17\u0e35\u0e48\u0e21\u0e31\u0e19\u0e44\u0e21\u0e48\u0e1e\u0e34\u0e2a\u0e39\u0e08\u0e19\u0e4c<\/th><\/tr><\/thead><tbody><tr><td>U<sub>c<\/sub><\/td><td>\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14\u0e17\u0e35\u0e48\u0e2d\u0e32\u0e08\u0e04\u0e07\u0e2d\u0e22\u0e39\u0e48\u0e15\u0e25\u0e2d\u0e14\u0e43\u0e19\u0e42\u0e2b\u0e21\u0e14\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19\u0e17\u0e35\u0e48\u0e1b\u0e23\u0e30\u0e01\u0e32\u0e28<\/td><td>\u0e04\u0e27\u0e32\u0e21\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e43\u0e19\u0e01\u0e32\u0e23\u0e1b\u0e25\u0e48\u0e2d\u0e22\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e40\u0e01\u0e34\u0e19\u0e2b\u0e23\u0e37\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e17\u0e35\u0e48\u0e2a\u0e48\u0e07\u0e44\u0e1b\u0e22\u0e31\u0e07\u0e42\u0e2b\u0e25\u0e14\u0e43\u0e19\u0e23\u0e30\u0e2b\u0e27\u0e48\u0e32\u0e07\u0e01\u0e32\u0e23\u0e01\u0e23\u0e30\u0e0a\u0e32\u0e01<\/td><\/tr><tr><td>U<sub>p<\/sub><\/td><td>\u0e23\u0e30\u0e14\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e17\u0e35\u0e48\u0e1b\u0e23\u0e30\u0e01\u0e32\u0e28\u0e20\u0e32\u0e22\u0e43\u0e15\u0e49\u0e40\u0e07\u0e37\u0e48\u0e2d\u0e19\u0e44\u0e02\u0e01\u0e32\u0e23\u0e17\u0e14\u0e2a\u0e2d\u0e1a\u0e41\u0e23\u0e07\u0e01\u0e23\u0e30\u0e15\u0e38\u0e49\u0e19\u0e17\u0e35\u0e48\u0e23\u0e30\u0e1a\u0e38<\/td><td>\u0e04\u0e27\u0e32\u0e21\u0e17\u0e19\u0e17\u0e32\u0e19\u0e15\u0e48\u0e2d\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e17\u0e33\u0e07\u0e32\u0e19\u0e15\u0e48\u0e2d\u0e40\u0e19\u0e37\u0e48\u0e2d\u0e07<\/td><\/tr><tr><td>I<sub>n<\/sub><\/td><td>\u0e2b\u0e19\u0e49\u0e32\u0e17\u0e35\u0e48\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e1b\u0e25\u0e48\u0e2d\u0e22\u0e15\u0e32\u0e21 nominal \u0e42\u0e14\u0e22\u0e43\u0e0a\u0e49\u0e23\u0e39\u0e1b\u0e04\u0e25\u0e37\u0e48\u0e19 8\/20 \u00b5s<\/td><td>\u0e04\u0e27\u0e32\u0e21\u0e2a\u0e32\u0e21\u0e32\u0e23\u0e16\u0e43\u0e19\u0e01\u0e32\u0e23\u0e17\u0e19\u0e15\u0e48\u0e2d\u0e1f\u0e49\u0e32\u0e1c\u0e48\u0e32\u0e42\u0e14\u0e22\u0e15\u0e23\u0e07<\/td><\/tr><tr><td>I<sub>\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14<\/sub><\/td><td>\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e1b\u0e25\u0e48\u0e2d\u0e22\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14\u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a SPD \u0e1b\u0e23\u0e30\u0e40\u0e20\u0e17 2 \u0e20\u0e32\u0e22\u0e43\u0e15\u0e49\u0e01\u0e32\u0e23\u0e17\u0e14\u0e2a\u0e2d\u0e1a 8\/20 \u00b5s \u0e17\u0e35\u0e48\u0e23\u0e30\u0e1a\u0e38<\/td><td>\u0e2b\u0e19\u0e49\u0e32\u0e17\u0e35\u0e48\u0e0b\u0e49\u0e33\u0e17\u0e35\u0e48\u0e04\u0e48\u0e32\u0e19\u0e31\u0e49\u0e19\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14<\/td><\/tr><tr><td>I<sub>imp<\/sub><\/td><td>\u0e2b\u0e19\u0e49\u0e32\u0e17\u0e35\u0e48\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e01\u0e23\u0e30\u0e15\u0e38\u0e49\u0e19\u0e17\u0e35\u0e48\u0e40\u0e01\u0e35\u0e48\u0e22\u0e27\u0e02\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e1a\u0e01\u0e32\u0e23\u0e17\u0e14\u0e2a\u0e2d\u0e1a\u0e1b\u0e23\u0e30\u0e40\u0e20\u0e17 1 \u0e41\u0e25\u0e30\u0e23\u0e39\u0e1b\u0e04\u0e25\u0e37\u0e48\u0e19 10\/350 \u00b5s<\/td><td>\u0e41\u0e17\u0e19\u0e17\u0e35\u0e48 U<sub>c<\/sub> \u0e2b\u0e23\u0e37\u0e2d U<sub>p<\/sub><\/td><\/tr><tr><td>U<sub>T<\/sub> \/ \u0e02\u0e49\u0e2d\u0e21\u0e39\u0e25 TOV<\/td><td>\u0e1e\u0e24\u0e15\u0e34\u0e01\u0e23\u0e23\u0e21\u0e20\u0e32\u0e22\u0e43\u0e15\u0e49\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e0a\u0e31\u0e48\u0e27\u0e04\u0e23\u0e32\u0e27\u0e17\u0e35\u0e48\u0e01\u0e33\u0e2b\u0e19\u0e14\u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a\u0e23\u0e30\u0e22\u0e30\u0e40\u0e27\u0e25\u0e32\u0e17\u0e35\u0e48\u0e23\u0e30\u0e1a\u0e38<\/td><td>\u0e2d\u0e19\u0e38\u0e0d\u0e32\u0e15\u0e43\u0e2b\u0e49\u0e17\u0e33\u0e07\u0e32\u0e19\u0e15\u0e48\u0e2d\u0e40\u0e19\u0e37\u0e48\u0e2d\u0e07\u0e17\u0e35\u0e48\u0e41\u0e23\u0e07\u0e14\u0e31\u0e19\u0e44\u0e1f\u0e1f\u0e49\u0e32\u0e19\u0e31\u0e49\u0e19<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e2a\u0e33\u0e2b\u0e23\u0e31\u0e1a\u0e04\u0e33\u0e2d\u0e18\u0e34\u0e1a\u0e32\u0e22\u0e17\u0e35\u0e48\u0e01\u0e27\u0e49\u0e32\u0e07\u0e02\u0e36\u0e49\u0e19\u0e40\u0e01\u0e35\u0e48\u0e22\u0e27\u0e01\u0e31\u0e1a\u0e1b\u0e23\u0e30\u0e40\u0e20\u0e17\u0e02\u0e2d\u0e07 SPD, \u0e01\u0e32\u0e23\u0e08\u0e31\u0e14\u0e2d\u0e31\u0e19\u0e14\u0e31\u0e1a\u0e01\u0e23\u0e30\u0e41\u0e2a\u0e01\u0e32\u0e23\u0e1b\u0e25\u0e48\u0e2d\u0e22\u0e41\u0e25\u0e30\u0e15\u0e33\u0e41\u0e2b\u0e19\u0e48\u0e07\u0e01\u0e32\u0e23\u0e15\u0e34\u0e14\u0e15\u0e31\u0e49\u0e07, \u0e43\u0e0a\u0e49 <a href=\"https:\/\/jutrion.com\/th\/surge-protective-device-guide\/\">\u0e04\u0e39\u0e48\u0e21\u0e37\u0e2d\u0e2d\u0e38\u0e1b\u0e01\u0e23\u0e13\u0e4c\u0e1b\u0e49\u0e2d\u0e07\u0e01\u0e31\u0e19\u0e01\u0e32\u0e23\u0e01\u0e23\u0e30\u0e0a\u0e32\u0e01\u0e02\u0e2d\u0e07 JUTRION<\/a>. \u0e1a\u0e17\u0e04\u0e27\u0e32\u0e21\u0e19\u0e35\u0e49\u0e08\u0e30\u0e21\u0e38\u0e48\u0e07\u0e40\u0e19\u0e49\u0e19\u0e44\u0e1b\u0e17\u0e35\u0e48\u0e01\u0e32\u0e23\u0e15\u0e31\u0e14\u0e2a\u0e34\u0e19\u0e43\u0e08\u0e17\u0e35\u0e48\u0e41\u0e04\u0e1a\u0e01\u0e27\u0e48\u0e32: \u0e01\u0e32\u0e23\u0e40\u0e25\u0e37\u0e2d\u0e01\u0e43\u0e19\u0e2b\u0e21\u0e39\u0e48\u0e04\u0e48\u0e32 U<sub>c<\/sub> 275 V, 320 V \u0e41\u0e25\u0e30 385 V.<\/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\">\u0e17\u0e33\u0e44\u0e21\u0e01\u0e32\u0e23\u0e08\u0e31\u0e14\u0e2d\u0e31\u0e19\u0e14\u0e31\u0e1a\u0e17\u0e31\u0e49\u0e07\u0e2a\u0e32\u0e21\u0e08\u0e36\u0e07\u0e1b\u0e23\u0e32\u0e01\u0e0f\u0e43\u0e19\u0e42\u0e04\u0e23\u0e07\u0e01\u0e32\u0e23 230\/400 V<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The three ratings exist because a low-voltage system does not present one perfectly fixed voltage under all operating and fault conditions. Supply tolerance, voltage regulation, harmonic distortion, neutral displacement, earth faults and the earthing arrangement can change the voltage applied to a protection mode. Product families also differ in their TOV behaviour and internal technology.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">For a nominal 230 V phase-to-neutral supply, the simple ratio is:<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>275 \/ 230 = 1.20, 320 \/ 230 = 1.39, and 385 \/ 230 = 1.67.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These ratios are useful for seeing the increasing continuous-voltage margin, but they are not a complete selection formula. They do not describe the site\u2019s maximum steady-state voltage, the protection mode, or how the SPD behaves during a TOV. Two SPDs with the same U<sub>c<\/sub> can also have different U<sub>T<\/sub>, \u0e04\u0e48\u0e32 U<sub>p<\/sub>, backup-protection and disconnection data.<\/p>\n\n\n\n<figure class=\"wp-block-table jutrion-table\"><table class=\"has-fixed-layout\"><thead><tr><th>U<sub>c<\/sub> class<\/th><th>Typical reason it enters the shortlist<\/th><th>Main benefit<\/th><th>Main check before approval<\/th><\/tr><\/thead><tbody><tr><td>275 V AC<\/td><td>The protection mode normally sees approximately 230 V and the product\u2019s TOV data suits the network<\/td><td>Tighter voltage margin often supports a relatively low protection level<\/td><td>Can it remain stable at the site\u2019s highest continuous voltage and survive the specified TOV?<\/td><\/tr><tr><td>320 V AC<\/td><td>The design needs additional operating-voltage margin, or the manufacturer assigns this class to the required network arrangement<\/td><td>More tolerance to sustained voltage elevation than a 275 V class<\/td><td>Is its U<sub>p<\/sub> still coordinated with the equipment impulse withstand voltage?<\/td><\/tr><tr><td>385 V AC<\/td><td>The connected mode or approved TOV strategy requires substantially more voltage margin<\/td><td>Reduced risk of unwanted operation from elevated power-frequency voltage<\/td><td>Does the higher class leave a sufficiently low effective protection level at the load?<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">This is a screening table, not a universal substitution chart. A 320 V device cannot automatically replace a 275 V device, and a 385 V device cannot be approved merely because it is less likely to react to an elevated mains voltage.<\/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-4\">Start with the Voltage Across Each Protection Mode<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Draw the SPD connection before choosing the cartridge. Mark the normal voltage across every mode and ask what voltage can appear there during the credible operating and fault states defined by the project.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-5\">Single-Phase 230 V, L\u2013N Protection<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD connected from line to neutral normally sees the phase-to-neutral voltage. In an ordinary, correctly regulated 230 V system, 275 V is commonly shortlisted. The approval still depends on the permitted supply range, site measurements where relevant, TOV requirements and the exact datasheet.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If the site regularly operates near or above the upper boundary assumed by the design, selecting 275 V from the nominal label alone can cause accelerated ageing or unnecessary thermal disconnector operation. The engineering response is not automatically \u201cfit 385 V.\u201d First determine whether the elevated voltage is a valid operating condition, a supply-quality problem, a neutral fault or an application outside the original design.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-6\">Three-Phase 230\/400 V, L\u2013N or L\u2013PE Protection<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In a 230\/400 V wye system, each phase is about 230 V to neutral and about 400 V to another phase. A module connected L\u2013N is therefore not continuously exposed to 400 V during normal operation. A module connected in another mode may face a different requirement.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This distinction is why pole count does not select U<sub>c<\/sub>. \u201cFour-pole SPD for a 400 V panel\u201d is incomplete. The specification must state the network configuration and protection circuit, such as 3+1 or 4+0, and identify the voltage across each module.<\/p>\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\/10\/02-three-phase-spd-3-plus-1-protection-modes-1024x341.webp\" alt=\"\" class=\"wp-image-2232\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/02-three-phase-spd-3-plus-1-protection-modes-1024x341.webp 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/02-three-phase-spd-3-plus-1-protection-modes-300x100.webp 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/02-three-phase-spd-3-plus-1-protection-modes-768x256.webp 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/02-three-phase-spd-3-plus-1-protection-modes-18x6.webp 18w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/02-three-phase-spd-3-plus-1-protection-modes.webp 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><em>Three-phase 3+1 SPD arrangement with L1, L2 and L3 protected to neutral and a separate N-PE module.<\/em><\/code><\/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-7\">Earthing System and Circuit Arrangement Change the Answer<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">The same 230\/400 V nominal supply can require a different SPD assembly depending on whether it is TN-C, TN-S, TT or IT. The important question is not only how many modules are installed, but which components are connected between which conductors.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-8\">TN Systems<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">TN-C and TN-S systems have different PEN or N\/PE connection points, so use an assembly declared for the specific TN arrangement. A 275 V cartridge is common for a 230 V protection mode, but its TOV performance still has to pass; 320 V or 385 V variants are used only where the required continuous-voltage or TOV margin supports them.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-9\">TT Systems and 3+1 Circuits<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A 3+1 arrangement commonly places voltage-limiting components from phase to neutral and a spark-gap-based component from neutral to PE. The phase cartridges are therefore selected for L\u2013N duty; the N\u2013PE component has different data. This arrangement can control TOV consequences in TT systems, but it must follow the applicable installation standard and manufacturer instructions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-10\">IT Systems<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In an IT system, healthy conductors can rise relative to earth after the first earth fault. Do not specify a 275 V L\u2013PE cartridge solely because the loads are called 230 V. Use an assembly declared for the IT arrangement and verify conductor-to-earth voltage, protection modes and TOV behaviour.<\/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\">The Real Trade-Off: Nuisance Ageing Versus Protection Level<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Choosing U<sub>c<\/sub> too low and choosing it too high create different problems.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-12\">If U<sub>c<\/sub> Is Too Low<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A metal-oxide varistor is voltage-dependent. Repeated or sustained operation too close to its continuous limit can increase leakage, temperature and ageing. A temporary overvoltage outside the declared capability can cause the internal thermal disconnector to operate, leaving the downstream circuit energized but no longer surge-protected. In a severe mismatch, the failure can be unsafe unless the product and backup protection clear it correctly.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A red indicator shortly after commissioning does not necessarily prove that the site experienced an exceptional lightning event. The investigation should include steady-state voltage, neutral integrity, wiring, TOV exposure, backup protection and whether the installed U<sub>c<\/sub> and circuit match the network.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-13\">If U<sub>c<\/sub> Is Too High<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A higher-U<sub>c<\/sub> varistor normally begins significant conduction at a higher voltage. Depending on the product design, this can raise U<sub>p<\/sub>. For example, one manufacturer\u2019s otherwise comparable single-pole Type 2 family declares U<sub>p<\/sub> at no more than 1.5 kV for its 275 V and 320 V versions, but no more than 1.75 kV for its 385 V version. That is a product example, not a universal conversion rule, but it shows why the higher number is not automatically superior.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The relevant protection at the load is not just the catalogue U<sub>p<\/sub>. Connection-lead inductance adds voltage while surge current rises. Long conductors can erase the apparent advantage of a lower U<sub>p<\/sub>. U<sub>c<\/sub>, \u0e04\u0e48\u0e32 U<sub>p<\/sub>, conductor length and equipment impulse withstand voltage must therefore be coordinated together.<\/p>\n\n\n\n<blockquote class=\"wp-block-quote jutrion-info-box is-layout-flow wp-block-quote-is-layout-flow\">\n<p class=\"wp-block-paragraph\"><strong>Selection principle:<\/strong> choose the lowest U<sub>c<\/sub> class that is approved for the maximum continuous voltage, protection mode, earthing arrangement and TOV duty. Then confirm that its U<sub>p<\/sub> and installed lead voltage remain below the protected equipment\u2019s impulse withstand requirement with an adequate margin.<\/p>\n<\/blockquote>\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\/10\/03-spd-uc-tov-up-selection-tradeoff-1024x341.webp\" alt=\"\" class=\"wp-image-2235\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/03-spd-uc-tov-up-selection-tradeoff-1024x341.webp 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/03-spd-uc-tov-up-selection-tradeoff-300x100.webp 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/03-spd-uc-tov-up-selection-tradeoff-768x256.webp 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/03-spd-uc-tov-up-selection-tradeoff-18x6.webp 18w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/03-spd-uc-tov-up-selection-tradeoff.webp 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><em>SPD Uc selection trade-off between low-voltage ageing and a higher downstream voltage protection level.<\/em><\/code><\/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-14\">Field Case: Why Moving Straight to 385 V Left the VFDs Exposed<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">An anonymized cold-chain packaging facility in Southeast Asia experienced repeated SPD disconnector operation on secondary 230\/400 V distribution panels during the first three months after commissioning. The indicators on several installed 275 V Type 2 cartridges changed to red. The local contractor assumed that frequent lightning surges were exhausting the SPDs and replaced the cartridges with 385 V versions, treating the higher U<sub>c<\/sub> as a heavier-duty rating.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Two months later, a grid-switching event was followed by dielectric failure in three variable frequency drives and two digital controller cards. The 385 V cartridges remained serviceable, forcing the investigation to separate the original nuisance disconnection from the later failure of protection coordination.<\/p>\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\/10\/04-385v-spd-vfd-field-case-1024x341.webp\" alt=\"\" class=\"wp-image-2233\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/04-385v-spd-vfd-field-case-1024x341.webp 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/04-385v-spd-vfd-field-case-300x100.webp 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/04-385v-spd-vfd-field-case-768x256.webp 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/04-385v-spd-vfd-field-case-18x6.webp 18w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/04-385v-spd-vfd-field-case.webp 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><em>Field case showing a 385 V SPD, 60 cm connection path and approximately 2.4 kV reaching downstream VFDs.<\/em><\/code><\/figcaption><\/figure>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-15\">Why the 275 V Cartridges Were Disconnecting<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Recorded phase-to-neutral voltage repeatedly reached 258\u2013262 V AC RMS and contained notable fifth-harmonic distortion. The investigation attributed rising varistor leakage and temperature to prolonged power-frequency stress rather than repeated lightning impulses. This does not mean every 275 V SPD will fail at 262 V: the response also depends on TOV data, waveform, ambient temperature and ageing. Here, the site measurements and product data had not been reviewed together.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-16\">Why the 385 V Replacement Was Not an Equivalent Upgrade<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The 385 V cartridges tolerated the elevated supply, but their declared U<sub>p<\/sub> was 1.8 kV versus no more than 1.35 kV for the original cartridges. The 60 cm connection path was estimated, for the assessed surge current and geometry, to add about 0.6 kV. The resulting 2.4 kV first-pass estimate did not exceed the drives\u2019 stated 2.5 kV impulse withstand, but it left almost no margin for tolerance, waveform and installation effects.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-17\">Resolution: Use the Middle Voltage Class and Shorten the Current Path<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The replacement used a JUTRION 320 V Type 2 configuration declared at U<sub>p<\/sub> \u2264 1.4 kV. Its U<sub>c<\/sub> provided approximately 22% margin over the recorded 262 V RMS, subject to confirmation against the product documentation and site TOV assessment. Busbar comb connections and optimized V-wiring reduced the total path from about 60 cm to less than 25 cm; under the same estimation method, inductive addition fell below approximately 0.25 kV and the effective protection estimate stayed below about 1.65 kV.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">No repeat nuisance disconnection or related controller damage was reported during the observation period. The correction combined sufficient continuous-voltage margin, a lower U<sub>p<\/sub> and a shorter discharge path instead of automatically selecting the highest U<sub>c<\/sub>.<\/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-18\">A Worked 230\/400 V Panel Comparison<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">For an illustrative 230\/400 V commercial board with separate N and PE conductors and a 3+1 SPD, review the candidates in this order:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Identify the mode voltage.<\/strong> Each phase module is connected L\u2013N, so it normally sees about 230 V, not 400 V.<\/li>\n\n\n\n<li><strong>Establish the highest continuous supply voltage.<\/strong> Use the project\u2019s supply tolerance and any verified site data. Do not treat an abnormal neutral condition as an ordinary continuous operating point.<\/li>\n\n\n\n<li><strong>Define TOV duty.<\/strong> Review the earthing system, plausible neutral and earth faults, and the U<sub>T<\/sub>-versus-time data required by the installation design.<\/li>\n\n\n\n<li><strong>Compare approved products.<\/strong> A 275 V version may provide adequate continuous and TOV performance. If it does not, the 320 V version may be evaluated. A 385 V version remains a candidate only if the higher margin is actually necessary.<\/li>\n\n\n\n<li><strong>Recheck protection performance.<\/strong> Compare U<sub>p<\/sub> for each exact model, then include the effect of the connecting conductors and coordination with downstream protection.<\/li>\n<\/ol>\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\/10\/05-spd-lead-length-v-wiring-comparison-1024x341.webp\" alt=\"\" class=\"wp-image-2234\" srcset=\"https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/05-spd-lead-length-v-wiring-comparison-1024x341.webp 1024w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/05-spd-lead-length-v-wiring-comparison-300x100.webp 300w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/05-spd-lead-length-v-wiring-comparison-768x256.webp 768w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/05-spd-lead-length-v-wiring-comparison-18x6.webp 18w, https:\/\/jutrion.com\/wp-content\/uploads\/2026\/10\/05-spd-lead-length-v-wiring-comparison.webp 1200w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><code><em>Comparison of a 60 cm SPD connection and optimized V-wiring under 25 cm for improved VFD protection.<\/em><\/code><\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">If 275 V passes the continuous-voltage and TOV checks, it normally remains the first candidate. Move to 320 V when additional margin is required and U<sub>p<\/sub> remains acceptable. Use 385 V only when the mode or TOV duty justifies it and the downstream protection calculation still passes.<\/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-19\">Read U<sub>c<\/sub>, \u0e04\u0e48\u0e32 U<sub>T<\/sub> and U<sub>p<\/sub> as One Set<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">An SPD datasheet should allow the designer to trace three different voltage questions:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>U<sub>c<\/sub>:<\/strong> What voltage may remain continuously across this protection mode?<\/li>\n\n\n\n<li><strong>U<sub>T<\/sub> or TOV characteristic:<\/strong> What happens at a stated power-frequency overvoltage and duration\u2014does the SPD withstand it or fail safely?<\/li>\n\n\n\n<li><strong>U<sub>p<\/sub>:<\/strong> To what declared level does the SPD limit a specified impulse at its terminals?<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Do not infer one value from another. After voltage compatibility is established, separately verify Type 1, Type 2 or Type 1+2 duty; I<sub>imp<\/sub>, I<sub>n<\/sub> \u0e41\u0e25\u0e30 I<sub>\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14<\/sub>; prospective short-circuit current; disconnection; backup protection; and remote indication.<\/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-20\">What to Put in an SPD Enquiry or Specification<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">\u201cNeed 4P 385 V SPD\u201d is not enough information for a reliable product match. Send the electrical context that determines the cartridge duty:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>nominal system voltage and frequency;<\/li>\n\n\n\n<li>single-phase or three-phase conductor arrangement;<\/li>\n\n\n\n<li>earthing system: TN-C, TN-S, TT, IT or another defined arrangement;<\/li>\n\n\n\n<li>required protection circuit, such as 1+1, 3+1 or 4+0;<\/li>\n\n\n\n<li>SPD type and installation position;<\/li>\n\n\n\n<li>required U<sub>c<\/sub>, TOV and U<sub>p<\/sub> performance;<\/li>\n\n\n\n<li>I<sub>imp<\/sub>, I<sub>n<\/sub> \u0e41\u0e25\u0e30 I<sub>\u0e2a\u0e39\u0e07\u0e2a\u0e38\u0e14<\/sub> requirements;<\/li>\n\n\n\n<li>prospective short-circuit current and upstream protection;<\/li>\n\n\n\n<li>remote contact, replaceable module and certification requirements; and<\/li>\n\n\n\n<li>destination market, quantity and project documentation needs.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u0e1b\u0e23\u0e30\u0e40\u0e20\u0e17 <a href=\"https:\/\/jutrion.com\/th\/spd\/\">JUTRION AC SPD range<\/a> includes Type 2 and Type 1+2 options for low-voltage distribution systems. A final model should be matched to the actual network and connection diagram rather than selected from the U<sub>c<\/sub> number in isolation.<\/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-21\">Common Questions About 275 V, 320 V and 385 V SPDs<\/h2>\n<\/blockquote>\n\n\n<div id=\"rank-math-faq\" class=\"rank-math-block\">\n<div class=\"rank-math-list\">\n<div id=\"faq-question-1791463372687\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question\">Can I use a 385 V SPD on a 230 V system?<\/h3>\n<div class=\"rank-math-answer\">\n\n<p>Possibly, but it is not automatically the best choice. Confirm that the product is declared for the network and protection mode, then compare its U<sub>p<\/sub> with the protected equipment. The extra U<sub>c<\/sub> margin is useful only if the design needs it and the resulting protection level remains acceptable.<\/p>\n\n<\/div>\n<\/div>\n<div id=\"faq-question-1791464255661\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question\">Is a 275 V SPD always correct for a 230 V supply?<\/h3>\n<div class=\"rank-math-answer\">\n\n<p>No. It is a common candidate for a mode that normally sees 230 V, but suitability depends on maximum continuous voltage, earthing system, TOV exposure, circuit arrangement and the exact datasheet.<\/p>\n\n<\/div>\n<\/div>\n<div id=\"faq-question-1791464321354\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question\">Why would an SPD fail when no lightning strike was reported?<\/h3>\n<div class=\"rank-math-answer\">\n\n<p>Possible causes include repeated switching surges, sustained overvoltage, a lost or unstable neutral, incorrect U<sub>c<\/sub>, wrong protection circuit, ageing, loose connections or inadequate backup coordination. A failed indicator is a reason to investigate the system, not merely to fit a higher-voltage cartridge.<\/p>\n\n<\/div>\n<\/div>\n<div id=\"faq-question-1791464332925\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question\">Does 320 V U<sub>c<\/sub> mean a 320 V nominal system?<\/h3>\n<div class=\"rank-math-answer\">\n\n<p>No. U<sub>c<\/sub> is the maximum continuous voltage across the SPD protection mode, not necessarily the nominal line-to-line or line-to-neutral system designation. Read it with the connection diagram.<\/p>\n\n<\/div>\n<\/div>\n<div id=\"faq-question-1791464348648\" class=\"rank-math-list-item\">\n<h3 class=\"rank-math-question\">Are U<sub>c<\/sub> and U<sub>CPV<\/sub> interchangeable?<\/h3>\n<div class=\"rank-math-answer\">\n\n<p>No. U<sub>CPV<\/sub> is used for photovoltaic DC SPD applications and must be selected from the maximum PV string voltage under the project\u2019s temperature conditions. For that task, use the separate <a href=\"https:\/\/jutrion.com\/th\/how-to-select-dc-spd-solar-pv\/\">DC SPD selection guide for solar PV<\/a>.<\/p>\n\n<\/div>\n<\/div>\n<\/div>\n<\/div>\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-22\">The Practical Selection Rule<\/h2>\n<\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\">Do not choose 275 V, 320 V or 385 V from the front label of the distribution board. First establish the voltage across each SPD protection mode, then verify the highest continuous voltage, earthing arrangement and TOV duty. From the ratings that pass those checks, choose the option that still gives adequate U<sub>p<\/sub> coordination at the protected equipment.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In many ordinary 230 V protection modes, that process begins with 275 V. It moves to 320 V or 385 V only when the network conditions and manufacturer data support the change. Higher U<sub>c<\/sub> is additional voltage margin\u2014not a universal measure of better surge protection.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-palette-color-9-color has-text-color has-link-color has-medium-font-size wp-elements-23\">\u0e40\u0e2d\u0e01\u0e2a\u0e32\u0e23\u0e2d\u0e49\u0e32\u0e07\u0e2d\u0e34\u0e07\u0e17\u0e32\u0e07\u0e40\u0e17\u0e04\u0e19\u0e34\u0e04<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/65314\" target=\"_blank\" rel=\"noopener\">IEC 61643-11:2025 \u2014 Low-voltage surge protective devices connected to AC low-voltage power systems<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/webstore.iec.ch\/en\/publication\/32531\" target=\"_blank\" rel=\"noopener\">IEC 61643-12:2020 \u2014 Selection and application principles for low-voltage SPDs<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.se.com\/ar\/es\/faqs\/FAQ000246782\/\" target=\"_blank\" rel=\"noopener\">Schneider Electric \u2014 IEC SPD parameters including U<sub>c<\/sub>, \u0e04\u0e48\u0e32 U<sub>p<\/sub> \u0e41\u0e25\u0e30 I<sub>n<\/sub><\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>275 V, 320 V or 385 V: The Short Answer For a 230\/400 V AC installation, a 275 V SPD is often the first candidate when its protection mode normally sees about 230 V, but it is not an automatic choice for every network. Use 320 V when the approved design needs more continuous-voltage or [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2236,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-2209","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-electrical-guides"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/posts\/2209","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/comments?post=2209"}],"version-history":[{"count":1,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/posts\/2209\/revisions"}],"predecessor-version":[{"id":2237,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/posts\/2209\/revisions\/2237"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/media\/2236"}],"wp:attachment":[{"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/media?parent=2209"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/categories?post=2209"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jutrion.com\/th\/wp-json\/wp\/v2\/tags?post=2209"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}