2-speed motor controls 1

[thinker]

We consider the usage of 2-speed motor (3x480V, 60 Hz, 6.6 kW, tapped windings YY, switching a number of poles from 2 to 4). This is a dynamometer blower motor, and we need to reduce a blower noise level at low load of the dynamometer. Blower motor supplier (Germany) stated two mandatory conditions of that motor operations: 1. We must start the motor only in low speed mode (4 poles) and 2. There should be a time delay (not specified) when switching from high speed to low speed mode. Unfortunately, there are some communication problems with this vendor, and it is difficult to get a clarification and explanation from them. Question to community: are these requirements common (and known)for 2-speed motors? We never used them before, so any thoughts would be greatly appreciated.

 

[jraef]

Yes they are common requirements for 2 speed motor controls.

Assuming it is a constant HP motor, in the high speed configuration you are trading torque for speed, so at high speed you have less torque and acceleration from a dead stop in that mode may cause an overload.

The time delay between speeds is so that any you eliminate any positive difference in relative frequency between the rotor and line frequency, otherwise it could cause a severe voltage spike. The delay typically needs to be long enough for the motor speed to drop to or below the low speed. Because every application has different inertia, friction, windage etc., this is something you need to observe and time yourself.

JRaef.com
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[thinker]

JRaef, thank you for advice, it was very helpful. Star for you.