Motor Failure & Reliability
The most common type of motor used in commercial and industrial applications.
What is the squirrel-cage induction motor?
The general condition that necessitates the use of reduced-voltage starting methods.
What is high starting current
The back and forth movement of a motor shaft is known as this.
What is end play?
The motor condition when one or more windings come into contact with the motor frame.
What is a grounded winding?
The two typical types of flexible couplings used to connect motor shafts to loads.
What are jaw and splined couplings?
A common indication of worn bearings in a motor.
What is excessive heat, noise, or vibration?
A common starting method that reduces current by connecting the motor windings first in a Wye configuration.
What is Wye-Delta?
The common configuration designation for heavy-duty commercial/industrial motors that are Totally Enclosed.
What are TE motors?
The condition in which two or more windings come into contact with each other.
What is a short circuit?
The brief start/stop procedure used during first-time startup to check the motor's direction of rotation.
What is bumping?
The NEMA standard for the maximum allowable voltage imbalance a motor should operate under.
What is 5%?
This method of starting uses a transformer with taps to reduce the voltage applied to the motor.
What is the Autotransformer method?
The test instrument used to check a motor's insulation for deterioration or resistance to ground.
What is the Megohmmeter?
A winding that has a break in its electrical path.
What is an open circuit?
What is often installed after proper alignment is verified to ensure the motor can be returned to the same position after removal?
What are dowel pins?
The single most damaging cause of motor failure, where one phase opens while the motor is running.
What is single-phasing?
A method that uses a resistor or reactor to reduce the voltage applied to the motor windings.
What is the Primary Resistor or Reactance method?
The motor frame must be connected to this when performing a motor insulation resistance test.
What is ground?
Besides heat, noise, or vibration, name one environmental factor that can be a common cause of motor failure.
What is moisture, dust, or dirt?
The procedure performed to establish a motor shaft's electrical center by running the motor with no load.
What is end play adjustment?
A motor is rated for 480V. The voltage variation should not exceed 10% of nameplate voltage, which equates to this amount in volts.
What is 48V? 480V x 0.10 = 48V
This method is used on dual-voltage motors by only energizing one set of parallel windings initially to limit current.
What is Part-Winding?
Name one specialized tool, other than a voltmeter or ammeter, used for motor maintenance according to the materials.
What is a Tachometer or a Vibration Tester?
If a motor's end play is not properly adjusted, it may cause damage to this critical motor component.
What are the bearings?
During the first coupled startup, the motor should be run for this amount of time in an unloaded condition before connecting the load.
What is one hour?