Electrical Speed Calculator
Convert mechanical speed to electrical speed and frequency using the motor's pole pair count.
Must be zero or greater.
A positive whole number (poles ÷ 2).
Assumption
Assumes a constant mechanical speed and a symmetric, sinusoidally-wound machine — typical for PMSM and BLDC drives under steady-state operation.
Equivalent electrical revolutions per minute: mechanical RPM × pole pairs.
Formula
Electrical frequency from mechanical speed
fe = n · P / 60
- fe
- Electrical frequency [Hz]
- n
- Mechanical speed [RPM]
- P
- Pole pairs [—]
Related angular quantities
ωm = n · 2π / 60 ωe = ωm · P ne = n · P
- ωm
- Mechanical angular speed [rad/s]
- ωe
- Electrical angular frequency [rad/s]
- ne
- Electrical speed [RPM (elec.)]
Poles vs. pole pairs
A motor's pole count is the total number of magnetic north and south poles around the rotor, and is always even. A pole pair is one north/south pair, so pole pairs = poles ÷ 2. A 2-pole motor has 1 pole pair, so its electrical frequency equals its mechanical rotation frequency. An 8-pole motor has 4 pole pairs, so the electrical waveform completes 4 full cycles for every single mechanical revolution — this is why higher pole-count motors produce a higher electrical frequency (and commutation rate) at the same shaft speed.
Worked example
An 8-pole motor (4 pole pairs) spinning at 1000 RPM:
- Electrical frequency: 1000 × 4 / 60 = 66.67 Hz
- Electrical speed: 1000 × 4 = 4000 RPM (elec.)
- Mechanical angular speed: 1000 × 2π / 60 ≈ 104.72 rad/s
- Electrical angular frequency: 104.72 × 4 ≈ 418.88 rad/s
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