What is the current of large 110–355 kW electric motors?

Large three-phase motors between 110 and 355 kW draw hundreds of amps at 400 V: in the HEM Motor catalogue the 110 kW models have nameplate currents of 185–196 A and the 315 kW models 522–526 A. At these ratings, the current is the first piece of data when planning the supply transformer and the starting arrangement.

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

The nameplate current of the 185 kW and 355 kW models and of the 315 kW 1,000 rpm model is not in our catalogue data, so it is not shown in the table; these values are confirmed from the nameplate with the order.

What do these currents change?

• A single motor can draw a current close to the entire connected load of a small plant; transformer rating and the short-circuit power of the network should be checked in advance.
• Direct-on-line starting is rarely suitable at these ratings; star-delta, a soft starter or a frequency converter is considered.
• At this level of current, parallel cables per phase and busbar connections come into play; terminal box entries are planned accordingly.
• Power factor (cos φ) correction is taken into account in the plant switchboard.

Example

The 160 kW 1,500 rpm 315L1-4 motor draws 271 A at 400 V. Assumption: star-delta starting. The winding current is 271 / √3 ≈ 156.5 A; the main and delta contactors are sized for this value, while the supply breaker and main cable are sized for 271 A.

For pre-order checks at high ratings, see the article on ordering a 315 kW motor. The models are in the cast iron frame electric motors category; send photos of the existing motor's nameplate and terminal box on WhatsApp and we will identify the equivalent together.