⚡ Motor & Ohm's Law Calculator

Resistance, power, full-load current & winding balance — for DC, synchronous & squirrel-cage motors.

1 · Ohm's Law & Power

Enter any two values — the other two calculate instantly.

Voltage (V)

Current (I)

Resistance (R)

Power (P)

Resistance

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Power

—

Voltage

—

Current

—

DC test: V ÷ I = resistance. Running AC motor: V ÷ I = impedance, not resistance.

2 · Winding Resistance & Balance Check

DC-measure each winding (T1-T2, T2-T3, T1-T3). Big imbalance = shorted turns / bad winding.

Winding 1 (Ω)

Winding 2 (Ω)

Winding 3 (Ω)

Average

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Max Imbalance

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Windings should read within ~5% of each other. More than that = suspect winding or connection.

3 · 3-Phase Power (kW / kVA)

Line voltage (V)

Line current (A)

Power factor

Real Power

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Apparent Power

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3-phase: kW = √3 × V × I × PF ÷ 1000 · kVA = √3 × V × I ÷ 1000.

4 · Motor HP → Full-Load Amps

Pick voltage, phase & horsepower for expected full-load current.

Horsepower (HP)

Voltage

Phase

Power factor

Efficiency

Estimated Full-Load Amps

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FLA ≈ HP × 746 ÷ (√3 × V × PF × eff). Estimate — size from the nameplate or NEC tables.

5 · Motor Speed (RPM)

Number of poles

Frequency

Synchronous RPM

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Approx. full-load RPM

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RPM = 120 × Hz ÷ poles. Real motors run a little slower (slip).