Motors & electrical
How to read an electric motor nameplate
Reviewed August 2026
Short answer
Photograph the whole nameplate straight-on. The fields a supplier needs are: manufacturer and part / catalogue number, power (kW), speed (r/min), voltage and frequency, frame size, mounting (e.g. B3, B5, B35), enclosure / IP rating, insulation class, duty (S1…), efficiency class (IE2/IE3/IE4) and any hazardous-area marking.
A clear, straight-on photo of the full nameplate answers most of a replacement motor quote. Here is what each field tells the supplier.
Identity
- Manufacturer and type / catalogue number — the fastest route to a direct replacement
- Serial number — lets the OEM confirm the exact build
Electrical
- Output power in kW (or HP)
- Voltage and frequency — e.g. 525 V / 50 Hz; note if dual-voltage
- Full-load current and power factor
- Speed in r/min — this tells you the pole count (2-pole ≈ 2900, 4-pole ≈ 1450, 6-pole ≈ 960)
- Efficiency class — IE2, IE3 or IE4
Mechanical
- Frame size — e.g. 132M, 200L, 315S. Sets the shaft height and roughly the mounting
- Mounting designation — B3 (foot), B5 (flange), B35 (foot & flange), V1 (vertical)…
- Shaft diameter and extension length if not standard for the frame
Environment and duty
- Enclosure / IP rating — IP55 is typical for mining; IP66 for washdown
- Insulation class (F, H) and temperature rise
- Duty type — S1 continuous, S2 short-time, etc.
- Hazardous-area marking — Ex d, Ex e, zone / gas group. This is critical and cannot be substituted casually.
Also send
The driven machine (pump, fan, crusher, conveyor) and its data, and whether the motor runs on a drive (VSD). A hazardous-area or drive-fed motor is quoted against its full marking, never as a generic drop-in.
Related questions
Send photos of what remains, the driven machine and its data, the physical dimensions of the motor (shaft diameter and length, mounting-hole pattern, overall length), and the terminal-box arrangement. An equivalent can often be worked back from the frame size and the driven load.
Usually yes — an IE3 or IE4 motor in the same frame, speed and mounting is normally a direct fit. Confirm the shaft, mounting and terminal-box position, and check the starter and cable are still suitable for the (often slightly lower) starting current.
