Question

For each question, circle your choice and write a sentence or two explaining why.

4. A single-phase motor is needed for a clock. The torque and efficiency do not matter, but it is critical that it run at a constant speed, even if the mechanical load varies or the motor bearings age. Of the motors below, which is the best choice? a) shaded pole motor b) capacitor start, capacitor run motor c) hysteresis motor d) permanent split capacitor motor Your rationale for your choice: __________________________________________________ ___________________________________________________________________________ ___

5. A motor that operates the fan in your friend’s window air conditioner is not working correctly. The fan blades spin, but not fast enough to move any appreciable amount of air. The motor is not overheated and doesn’t smell burned. When you switch the unit off, and manually spin the fan, it moves freely. While holding the fan, you switch the unit on – it has poor torque. Checking the motor, you see one capacitor, but the value is small, 6 microfarads. The most likely problem is a) bad centrifugal switch b) bad rotor bearings c) bad start capacitor d) bad run capacitor e) burned start windings f) burned run windings Your rationale for your choice

Answer 1