IE4 AC Motor

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Running an IE4 AC Motor on a Drive

An IE4 AC motor holds its rated efficiency at the frequency it was designed for and most of these machines now spend their working lives behind a variable speed drive rather than straight across the line so the drive settings belong in the specification next to the class
DRG Motor supplies IE4 units for that duty where the saving comes from matching the speed to the process instead of throttling flow at a valve or closing a damper and then paying for the resistance every hour of every shift
On a centrifugal load a modest reduction in speed cuts the power drawn by far more than the same reduction on a conveyor which is why pump and fan drives are the first ones converted in almost every plant and why the payback figures quoted for one duty never transfer to the other

What the Class Delivers

  • Lower power draw for the same shaft output because the class is measured not claimed

  • Less waste heat which keeps the winding cool when the drive holds the motor at part speed for hours

  • Running cost that appears on the electricity bill rather than on the purchase invoice

  • Frame and bearing strength for the shock a drive removes at start but not at stop

  • Insulation and construction suited to being fed from a drive rather than from the line

Duties That Suit Variable Speed

IE4 AC motors earn their keep where the load moves through the day rather than sitting at one point and the size of the saving follows the shape of that movement rather than the size of the motor

Pump groups that follow demand rather than a valve
Fans and ventilation running at part flow for most of the shift
Compressor packages with variable capacity control
Conveyor and material handling with soft starting
Process plant where line speed is set from the controller

What the Plant Notices

The meter is where the change shows first and by the largest amount
Holding a pump at the speed the process needs removes the throttling loss entirely
A soft start every morning saves couplings belts and gearboxes as much as it saves current
The payback is quickest on drives that never stop and slowest on those started twice a shift

Sizing One Correctly

An IE4 AC motor is worth its price where the drive runs long hours and the load varies and it is worth rather less on a machine that starts twice a shift and runs flat out in between
Send the duty cycle the speed range and the behaviour of the load at start and the model can be confirmed together with a plain answer on whether a lower class would do the same work for less money on that particular machine