Free electrical engineering tools
Turn electrical inputs into usable design parameters.
A connected set of engineering calculators for circuit protection, motor control, surge protection, voltage monitoring, and solar DC applications.
25parameter tools
6engineering categories
IECfocused reference
JUTRION parameter path Reference mode
01 / InputProject dataLoad · source · installation
→
02 / ProcessEngineering checkFormula + conditional logic
→
03 / OutputRequired parametersCurrent · rating · limits
Direct calculationNumeric resultFormula-derived
Conditional checkSelection rangeRequires verification
Guided workflow
The JUTRION calculation chain
Move from source and load data to protection parameters through smaller checks that can be reviewed independently.
01Calculate load currentPower, voltage and phase → Ib→
02Estimate breaker ratingIb, margin and cable Iz → In→
03Check fault currentSource impedance → prospective Isc→
04Confirm device dutyIsc and voltage → Icu check✓
Protection relationshipIb ≤ In ≤ Iz+Icu ≥ prospective fault current
Engineering calculators
Find the right calculation
JT–CP–01Direct calculation
Circuit protection
Short-Circuit Current & Icu Calculator
Estimate transformer-secondary terminal fault current, then compare it with the breaker breaking capacity at the operating voltage.
InputskVA · VLL · Z% · phase
→OutputsIn · Isc · Icu check
Optional: upstream contribution and feeder impedance for a fuller result.
Open calculator →JT–CP–02Direct calculation
Circuit protection
Circuit Breaker Sizing Calculator
Calculate design current and screen a standard breaker rating against the cable current-carrying capacity.
InputskW/kVA/A · V · PF · Iz
→OutputsIb · In · Ib≤In≤Iz
Separated: B, C, or D curve suitability is checked in the inrush tool.
Open calculator →JT–CP–03Conditional check
Circuit protection
MCB Inrush & Curve Checker
Compare equipment inrush and available fault current with the magnetic-trip bands of B, C, and D curves.
InputsIn · inrush · duration · Isc
→Outputsband comparison · screen
Not a guarantee: final performance follows the exact manufacturer curve.
Open calculator →JT–SV–01Conditional check
Surge & voltage
SPD Parameter Selection Check
Translate supply arrangement, installation point, lightning exposure, and equipment withstand into a preliminary SPD requirement.
Inputsstandard · V · TN/TT/IT · location
→Outputstype · Uc · Up · connection
Important: Up is a coordination target and product value, not calculated from voltage alone.
Open calculator →JT–PD–01Direct calculation
Motor & switching
ATS Sizing Calculator
Convert the load into design current, the AC-31/AC-33 category, a standard ATS rating, and the pole configuration.
InputskW/kVA · V · PF · character
→OutputsA · category · rating · poles
Decision: switched neutral and poles depend on the earthing and source.
Open calculator →JT–MC–02Direct calculation
Motor & switching
Generator Capacity for ATS
Estimate generator kW and kVA from diversified running load, the largest starting step, reserve, and environmental derating.
Inputsrun kW · start kVA · reserve
→Outputsgenset kW/kVA · ATS A
Required: confirm voltage dip and transient with the generator maker.
Open calculator →JT–CP–07Calculation + check
Circuit protection
Breaker Accessory Power Calculator
Estimate control-supply demand for shunt trips, undervoltage releases, motor operators, and related breaker accessories.
Inputsaccessory · coil V · VA · qty
→Outputspeak VA · steady VA · margin
Compatibility: series, frame, AC/DC, contacts, and mounting must match.
Open calculator →JT–CP–05Conditional check
Circuit protection
AFDD Requirement & Selection
Collect circuit and market information to define an AFDD or integrated AFDD-RCBO requirement and architecture.
Inputsmarket · premises · circuit · In
→Outputsstatus · architecture · rating
Not universal: whether AFDD is required depends on local rules.
Open calculator →JT–DC–01Direct calculation
Solar & DC
PV String Voltage Calculator
Calculate cold-condition string open-circuit voltage and screen the module count against inverter voltage limits.
InputsVoc · βVoc · Tmin · Vdc max
→Outputscold Voc · max modules
Required: use module and inverter datasheet limits.
Open calculator →JT–DC–07Calculation + check
Solar & DC
PV DC ATS Calculator
Calculate DC design current and organize the voltage, pole, source, and transfer requirements for a solar or battery DC ATS.
InputskW/A · Vdc · sources · polarity
→OutputsA · Ue · poles · check
DC-specific: verify switching, isolation, and arc interruption at Vdc.
Open calculator →JT–DC–02Calculation + check
Solar & DC
DC MCB & MCCB Rating Calculator
Calculate DC design current and screen rated current, operating voltage, poles, cable capacity, and breaking capacity.
Inputssource · Idc · Vdc · Iz · Isc
→OutputsIn · Ue · poles · Icu
Critical: DC poles and series connection follow the breaker documentation.
Open calculator →JT–DC–03Direct calculation
Solar & DC
PV String Fuse Rating Calculator
Calculate a reference gPV fuse-current range and compare it with the module maximum series-fuse rating.
InputsIsc · strings · factor · max fuse
→Outputsmin A · max A · pass/fail
Standard route: design multipliers selectable for the applicable standard.
Open calculator →JT–DC–04Direct calculation
Solar & DC
PV Combiner Box Rating Calculator
Aggregate string current and voltage into reference input-fuse, output-device, busbar, isolator, and SPD requirements.
Inputsstrings · Isc · cold Voc
→Outputsfuse · output A/V · SPD
System tool: ratings remain subject to enclosure temperature.
Open calculator →JT–DC–05Calculation + check
Solar & DC
PV DC Isolator Rating Calculator
Screen minimum voltage, current, utilization category, and pole configuration for a PV array isolation point.
Inputscold Voc · Isc · duty · topology
→OutputsUe · Ie · poles · category
Product-specific: verify the switching configuration at Vdc.
Open calculator →JT–DC–06Calculation + check
Solar & DC
PV SPD Minimum Ucpv Calculator
Derive a minimum continuous operating voltage from the cold-condition array voltage, then screen SPD type and connection topology.
Inputscold Voc · topology · earthing
→Outputsmin Ucpv · type · connection
Do not use nominal: the max temperature-corrected Voc governs.
Open calculator →JT–MC–01Direct calculation
Motor & switching
AC Contactor Motor Sizing
Estimate motor full-load current and a preliminary AC-3 operational-current requirement for normal starting and stopping duty.
InputskW · V · phase · η · PF
→OutputsFLC · minimum Ie
Product stage: coil, poles, auxiliaries, and life are selected after.
Open calculator →JT–MC–03Calculation + check
Motor & switching
Motor Overload Relay Setting
Translate motor nameplate current and application duty into a preliminary overload setting and trip-class check.
Inputsnameplate A · SF · start · ambient
→Outputssetting · band · trip class
Motor data governs: use the nameplate current for final adjustment.
Open calculator →JT–SV–02Conditional check
Surge & voltage
Voltage Threshold & Delay Setting
Build a preliminary voltage window, trip delay, and reconnection delay from the equipment tolerance and application behavior.
InputsVn · window · application
→OutputsU</U> · delay range
Application setting: delay rides through disturbances, not calculated from load.
Open calculator →JT–PD–02Direct calculation
Power distribution
Load Current & Power Calculator
Convert between kW, kVA, and current for DC, single-phase, and balanced three-phase loads.
Inputsmode · kW/kVA/A · V · PF
→OutputsA · kW · kVA
Supports: preliminary sizing for breakers, ATS, contactors, CTs.
Open calculator →JT–PD–03Direct calculation
Power distribution
Cable Voltage Drop Calculator
Estimate conductor voltage drop and percentage loss for DC, single-phase, and three-phase circuits.
InputsA · V · length · mm² · material
→OutputsΔV · Vd% · end voltage
Boundary: resistance and reactance must match the conductor.
Open calculator →JT–PD–04Direct calculation
Power distribution
Cable Derating & Iz Calculator
Combine correction factors and check whether the corrected cable capacity remains above the selected breaker rating.
Inputsbase Iz · Ca · Cg · Ci
→Outputscorrected Iz · In≤Iz
Required: base ampacity and factors from the adopted wiring tables.
Open calculator →JT–PD–05Direct calculation
Power distribution
Transformer Current Calculator
Calculate transformer line current on both sides from the kVA rating, voltage, and phase arrangement.
InputskVA · primary V · sec V · phase
→Outputsprimary A · secondary A
Supports: preliminary CT, ATS, MCCB, and ACB planning.
Open calculator →JT–PM–01Calculation + check
Power metering
CT Ratio & Burden Calculator
Select a reference CT ratio and estimate total secondary burden from meters, relays, and connecting leads.
Inputsprimary A · 1/5 A · lead · VA
→Outputsratio · burden VA · use
Product check: accuracy class and saturation need the exact CT data.
Open calculator →JT–CP–04Conditional check
Circuit protection
RCCB & RCBO Parameter Check
Organize residual-current waveform, protection purpose, load current, and expected standing leakage into a preliminary requirement.
Inputsload · waveform · leakage · poles
→OutputsRCD type · IΔn · In check
Code dependent: sensitivity and selectivity follow the market rules.
Open calculator →JT–CP–06Calculation + check
Circuit protection
ACB Frame & LSIG Worksheet
Build preliminary frame-current and LSIG setting ranges from feeder load, conductor capacity, fault level, and coordination.
InputsIb · Iz · Isc · downstream
→Outputsframe · Ir · Isd · Ii · Ig
Coordination study: final settings need manufacturer curves.
Open calculator →No matching calculator yet.Try a broader term such as “current”, “breaker”, “motor”, or “voltage”.
After the calculation
Have the parameters but still need a suitable product?
Send the calculation summary to JUTRION when you need help checking an available configuration for the destination market.