How many amps do medium-sized three-phase electric motors (5.5–22 kW) draw?

Three-phase motors between 5.5 and 22 kW draw roughly 10 A to 43 A at 400 V; the current per kW lies in the 1.7–2.2 A band. The nameplate currents of the models in the HEM Motor catalogue are shown below.

Values are the nameplate ratings of the models in the HEM Motor catalogue; they may differ for other brands or series.

Points to watch in this power range

• All models are rated 400/690 V and run in delta (Δ) on a 400 V supply, so star-delta starting can be used.
• 5.5–11 kW motors are offered in aluminium and cast iron frames, 15–22 kW in cast iron; in the catalogue both frames have the same nameplate current at the same power and speed.
• At start-up the current rises to several times the nameplate value; fuses and breakers are chosen to withstand this brief current as well.

Example: interpreting a measured current

The 11 kW 1,500 rpm 160M-4 motor has a nameplate current of 20.4 A. Assumption: the supply is 400 V and balanced, the motor is delta-connected. A reading clearly below the nameplate value on every phase shows the motor is running at part load; however, current does not fall in direct proportion to load, as the motor also draws a considerable current at no load. A reading permanently above 20.4 A points to overload, low voltage or mechanical strain. If there is a clear difference between phases, voltage unbalance is investigated. For the meaning of no-load current see the question on the current a motor draws at no load.

The measurement should be taken by a qualified electrician with a clamp meter on the cable, with the panel covers closed. You can view the models in these ratings with their current prices on the buy electric motors page, or send a photo of your existing motor's nameplate on WhatsApp and ask for its equivalent.