Motor Controls, IEC vs. NEMA
William & Patti FeldmanNEMA controls are primarily used in the North American market. IEC controls, which are internationally accepted and readily available all over the world, are, however, gaining significant market share in the U.S.
Though both NEMA and IEC motor controls are listed in accordance with UL standards for North American use, differences between them can affect how a particular motor control meets customer expectations.
For the same ratings, IEC motors are 30% - 80% more compact than NEMA motors and save 20% to 60% panel space.
However, NEMA controls have a reserve capacity built into the sizing system, supporting use of a lower rated motor that can accommodate higher duty rates, enabling longer product life in applications with high duty cycle rates. For example, a 10 hp NEMA motor at 480 volts has the capacity for 30 amps.
With IEC motor controls, the device is matched to the application. Reserve capacity is not built in, resulting in the need for specifying a higher rated motor to accommodate heavy duty cycles. For the same amp capacity, the application would possibly need a 20 hp motor at 480 volts to accommodate the same frequent initial surges, notes Tom Fowler, staff product specialist for motor control products at Schneider Electric.
Another notable differentiator between NEMA and IEC motor controls is how worn out parts are addressed. For NEMA motor controls, for which serviceability and maintainability are generally considered strengths, there are a wide variety of replacement parts (and field accessories) and parts can be individually changed, though that can require skilled labor.
There are generally no replacement parts for IEC contactors under 100 amps. If a part wears out, the entire unit requires change-out, but that can usually be handled by maintenance staff.
Photo courtesy of Schneider Electric