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Electric Motors/Red Star/Delta Radial Arm Saw Motor Blues

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Koiman wrote at 2016-08-15 21:41:00
What you are describing is a text-book example of a bad centrifugal switch.  This switch is closed when the motor is not turning and allows voltage to pass from the start capacitor to the start windings of the motor.  This capacitor causes the phase shift in the motor windings and a magnetic field that is out of phase with the magnetic field of main motor windings.  The result of this is torque, used to get the motor up to base speed.  As the motor builds speed, the switch should open, removing the capacitor from the start circuit.  When this doesn't happen, the capacitor stays energized and causes the start windings to remain phase shifted from the run windings.  This causes CEMF.  This also allows start windings and start capacitor to stay at in-rush current values, which are 5 times nameplate motor current.  The result of all this current is fried capacitor and potential damage to start windings.  Remove power from saw and check centrifugal switch.  It should be located opposite the motor shaft blade mounts on.  In most cases, the switch will have a large build-up of saw-dust on it, preventing correct operation.


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Harcharan Singh Diocee

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Electric motor winding redesign, AC and DC. Troubleshooting, motors controls generators. Vibration analysis, dynamic balancing, root cause analysis: electrical and mechanical.

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thirty five years electro-mechanical and Senior Management

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Journeyman Motor Rewinder, Millwright, Industrial Electrician, Vibration Analyst level II. Certified Electrical Technician ASTTBC, FSR Class B, in BC. Laser alignment specialist. Marine machinery repairs. Business Management Certificate. Last 19 yrs as Plant Manager

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