Why EC Motors Are More Efficient than AC Motors

What Is an EC Motor?

Electronically commutated (EC) motors are highly efficient, programmable, brushless DC motors utilizing a permanent magnet rotor and a built-in inverter. Basically, it is a DC motor (in a DC motor the mechanical commutation switches the direction of the current) with a built-in VFD and a DC to AC transformer. However in EC motors, the mechanical commutation and the brushes are replaced by an electrical commutation. The major advantages are that they are extremely efficient, especially at reduced speeds compared to traditional motors. Also, they have a built-in speed controller eliminating the need for a separate VFD. (At this time they are only available up to about 6.5 hp.) 

Why are EC Motors more efficient than AC Motors? 

• EC motors are electronically commutated synchronous motors. No slip between electrical rotating fields (stator) and mechanical speed on shaft (rotor) due to the permanent magnets. (Slip means that the speed of the electrical rotating fields is higher than the mechanical speed on shaft.)
• Insignificant rotor losses, rotor magnet field is created by the permanent magnets.
• With an asynchronous AC motor, the rotor magnet field is caused by an induced current in the short circuited rotor windings Losses.
• All TMI external rotor motors are asynchronous AC motors (Slip)
• Most of these are voltage controllable, so we say the motors are “soft” Higher Slip (Higher Losses) 

Download the TMI ECblue Motor Brochure.