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The centrifugal start motor
This type of motor is an induction motor. The difference between this and other motors is that the start winding is energized by a mechanical switch. This switch is normally closed so that when the motor is started, the start winding will be energized. As the motor speeds up to 75% of its normal speed, weights on the rotor, (note the pic above left) move against the springs and a disc moves out that opens the switch (bottom left).
These motors are commonly used as fan duty motors. The have higher starting torque than PSC motors, so they can be used for belt drive fans that have heavy blower wheels. If more torque is necessary, this type of motor can be ordered with up to 3 start capacitors. For a look at how this motor works, check the video below.
These motors are commonly used as fan duty motors. The have higher starting torque than PSC motors, so they can be used for belt drive fans that have heavy blower wheels. If more torque is necessary, this type of motor can be ordered with up to 3 start capacitors. For a look at how this motor works, check the video below.
Troubleshoot of the centrifugal start motor.
Beyond the usual bearing failures common to all motors, this motor has some special problems.
Most of these problems are connected to the start switch. These motors sometimes operate in dirty conditions. If the start switch gets enough dirt in it, it may not make. In this case, the start winding does not energize. The motor will hum but will not start. If left on for a minute or so, the internal overload will open to shut it down. There is an interesting way to determine if this has happened. If the motor is cool to the touch (overload reset), you can lightly strike the side of the motor with a hammer. That may shake loose the switch and get the motor started. This only a temporary fix and just tells you what the problem is. The switches are not available for most motors and motor will have to be replaced.
Another problem is the switch sticks closed. This problem usually results in a burned up start winding.
If the rotor shaft does not move easily then, of course, the bearings have failed. The video below illustrates problems with this motor.
Most of these problems are connected to the start switch. These motors sometimes operate in dirty conditions. If the start switch gets enough dirt in it, it may not make. In this case, the start winding does not energize. The motor will hum but will not start. If left on for a minute or so, the internal overload will open to shut it down. There is an interesting way to determine if this has happened. If the motor is cool to the touch (overload reset), you can lightly strike the side of the motor with a hammer. That may shake loose the switch and get the motor started. This only a temporary fix and just tells you what the problem is. The switches are not available for most motors and motor will have to be replaced.
Another problem is the switch sticks closed. This problem usually results in a burned up start winding.
If the rotor shaft does not move easily then, of course, the bearings have failed. The video below illustrates problems with this motor.