5:1speed range required
2:1self-ventilated limit
IC416forced cooling solves it
The duty
A process line needs a constant 49 Nm from 290 to 1,450 rpm (10 to 50 Hz on the inverter), with occasional running to 60 Hz.
The motor
EM3-132M-4-7.5: MN 49.4 Nm, IE3, Class F insulation with Class B rise. EMPD's standard guidance for inverter duty is variable torque 10:1 and constant torque 2:1 with a self-ventilated (IC411) motor.
The problem
The shaft-mounted fan's airflow falls with speed. At 25 Hz (2:1) the motor still carries full torque within its thermal limit; at 10 Hz it would not. Oversizing helps a little but wastes efficiency at the main operating point.
The solution
- Forced ventilation (IC416): a separately powered fan cools the motor at any speed, so full torque is available down to 10 Hz.
- Above 50 Hz the inverter weakens the field: torque falls in proportion to 50 ÷ f. At 60 Hz, 49.4 × 50 ÷ 60 = 41 Nm is available, enough for occasional high-speed running at reduced load.
- Insulation: Class F VPI windings cope with inverter voltage peaks; with long motor cables, fit an output reactor or dv/dt filter at the drive.
10–50 Hz constant 49.4 Nm with IC416 forced cooling
50–60 Hz 49.4 × 50/f → 41 Nm at 60 Hz (constant power)
Application study: an engineering example worked by EMPD with catalogue data. Your application is confirmed by our engineers before quotation. Send us your duty.
