Unit 20 Troubleshooting Electric Motors Flashcards
If a sleeve bearing fails in a small, fractional horsepower motor, the motor is generally replaced. True or false
True
An open winding in an electric motor means that
A wire in one winding is broken.
There is a short circuit in an electric motor winding when
A winding conductor is worn bare and touches another part of the conductor that is also bare.
An open winding or a shorted winding can be determined with which instrument?
An ohmmeter.
A decrease in resistance will cause the amperage to
Increase
A ______ may be used to detect resistances in the millions of ohms.
Megohmmeter
What size of resistor is recommended for shorting across an electrical motor capacitor before checking with an ohmmeter?
A 20,000 ohm, 5 Watt resistor is recommended.
. To determine the capacitance of a capacitor, a _____ should be used.
Capacitor tester
State the physical differences between a run and a start capacitor.
A run capacitor is a metal, oil filled can, whereas a start capacitor is dry and the shell is paper or plastic.
In a three-phase motor in good operating condition, the resistance
Should be the same across all three windings.
Describe what may happen to an electric motor if the drive belt is too tight.
A drive belt that is too tight will strain the bearings so that they wear out prematurely.
A loose connection may result in _____ voltage and _____ current at the motor.
Low,high
. The amperage can be checked with a _____ ammeter.
Clamp-on.
Electric motor roller and ball bearing failure often can be determined by the
Bearing noise.
Motor bearings ______ by the air-conditioning and refrigeration technician.
Are occasionally replaced.
An open winding in an electric motor means that
A wire in one winding is broken.
If there is a decrease in resistance in the run winding,
The motor may draw too much current while it is running.
PSC means
Permanent split-capacitor
Motor bearing failure with roller and ball bearings can often be identified by the
Bearing noise
Mini motors fail because of over tighten belts and incorrect alignment true or false
True
The belt tension gauge uses two
O-rings.
when using the gauge the center to Center measurements must be taken between the
Two shafts
If the drive pulley and driven pulley are not aligned, a strain is imposed on a ____________ of the shaft
Drive mechanism
the pulley maybe aligned with the help of a
straightedge
when the problem is the pulley or drive mechanism, the air conditioning, heating, and Refrigeration technician or motor expert may be responsible for repair
Technician
there are three common electrical motor problems
an open winding
A short circuit from Winding to winding
a short circuit from the winding to ground
open windings in a motor can be found with an
Ohmmeter
Most electrical problems with an electrical motor are _____, _____, and _____.
shorted windings; open windings or grounded windings
If the resistance of the run winding decreases, the ____
Motor will draw too much parent while it’s running
If I condenser fan motor grounds out, it will usually ___
Keep running as the current is only going to ground
