All-in-One Motor Calculator
Professional Electrical Engineering Tool | IEEE/IEC Standards
CircuitSecrets.com
Common Input Parameters
V
A
HP/kW
pu
%
Hz
RPM
m
°C
Formulas:
Single Phase: P = V × I × PF × η | Three Phase: P = √3 × V × I × PF × η
Motor Power Calculations
Formula: Pout = V × I × PF × η (1Φ) | Pout = √3 × V × I × PF × η (3Φ)
HP Conversion: HP = kW / 0.746
HP Conversion: HP = kW / 0.746
Full Load Current (FLC)
IEC Standards: FLC calculation based on motor power, voltage, efficiency and power factor.
Formula: IFLC = Pout / (√3 × V × PF × η) [3Φ] | IFLC = Pout / (V × PF × η) [1Φ]
Formula: IFLC = Pout / (√3 × V × PF × η) [3Φ] | IFLC = Pout / (V × PF × η) [1Φ]
Cable Size Selection
Standards: IEC 60364 / BS 7671 | Derating Factors: Temperature, Installation Method
Rule: Selected cable must carry FLC with derating applied
Rule: Selected cable must carry FLC with derating applied
Voltage Drop Calculation
Limit: 5% maximum (IEC/IEEE)
Formula: Vdrop = (2 × L × I × R × cos φ) / 1000 [1Φ] | Vdrop = (√3 × L × I × R × cos φ) / 1000 [3Φ]
Formula: Vdrop = (2 × L × I × R × cos φ) / 1000 [1Φ] | Vdrop = (√3 × L × I × R × cos φ) / 1000 [3Φ]
Protection Devices
Standards: IEC 60947 / BS 88 | MCB: 1.25 × FLC | MCCB: 1.25 × FLC
Contactor: 1.5 × FLC | Overload: 1.15 × FLC | Fuse: 1.5 × FLC
Contactor: 1.5 × FLC | Overload: 1.15 × FLC | Fuse: 1.5 × FLC
Starting Current
DOL: 5-7 × FLC | Star-Delta: 2.5-3.5 × FLC (starting) / 1.73 × FLC (running)
Soft Starter: 2.5-4 × FLC | VFD: 1.2-1.5 × FLC
Soft Starter: 2.5-4 × FLC | VFD: 1.2-1.5 × FLC
Torque & Slip
Torque: T = 9550 × kW / RPM (IEC Standard)
Slip: S = (Ns - Nr) / Ns × 100%
Synchronous Speed: Ns = 120 × f / P
Slip: S = (Ns - Nr) / Ns × 100%
Synchronous Speed: Ns = 120 × f / P
⚠️ Disclaimer:
This calculator is for estimation purposes only. Always verify with motor nameplate data and consult local electrical codes (NEC, IEC, BS 7671) before installation. Professional engineering judgment required.
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