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On a 400 V supply, the current of small three-phase motors ranges from 0.64 A to 8.99 A depending on power and number of poles: a 0.25 kW motor draws less than 1 A, a 4 kW motor around 7.5–9 A. The table below shows the nameplate currents of the models in the HEM Motor catalogue.
| Power (kW) | 3,000 rpm (A) | 1,500 rpm (A) | 1,000 rpm (A) |
|---|---|---|---|
| 0.25 | 0.64 | 0.66 | 0.77 |
| 0.37 | 0.89 | 0.92 | 1.04 |
| 0.55 | 1.24 | 1.31 | 1.43 |
| 0.75 | 1.64 | 1.75 | 1.93 |
| 1.1 | 2.31 | 2.48 | 2.69 |
| 1.5 | 3.06 | 3.30 | 3.59 |
| 2.2 | 4.35 | 4.52 | 5.09 |
| 3 | 5.71 | 6.02 | 6.84 |
| 4 | 7.45 | 7.95 | 8.99 |
Values are the nameplate ratings of the models in the HEM Motor catalogue; they may differ for other brands or series.
How to read the table
At the same power, a 6-pole (1,000 rpm) motor draws more current than a 2-pole (3,000 rpm) one; the low-speed motor has a higher magnetising current and a lower power factor (cos φ). For example, at 0.75 kW the 3,000 rpm model draws 1.64 A and the 1,000 rpm model 1.93 A. The electricians' rule of thumb of "2 A per kW" does not hold in this range; for 0.25–1.1 kW motors the current per kW rises to 2.1–3.1 A.
The connection changes the current
The 0.25–3 kW models are rated 230/400 V: on a 400 V supply they are connected in star (Y) and draw the current shown in the table. The 4 kW models are rated 400/690 V and are connected in delta (Δ) at 400 V. If the terminal links are fitted wrongly, the motor either lacks power or draws excessive current.
Example: protection setting
The 1.5 kW 1,500 rpm 90L-4 motor has a nameplate current of 3.30 A. Assumption: the motor is star-connected at 400 V and fully loaded. The motor protection circuit breaker is chosen so that its setting range includes 3.30 A, and it is set to 3.3 A; setting it higher leaves the winding unprotected. For details see the question on what current a thermal overload relay should be set to.
All models in these power ratings are listed with their current prices in the aluminium frame electric motors category. Send a photo of your old motor's nameplate on WhatsApp and we will identify the equivalent model from its current and connection data.