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L1 L2 Checking
Single Phase
Power
Fig.18
}
These tests should give
a
reading of full line voltage.
Three Phase Motors
Touch a voltmeter lead to:
• Power leads L1 and L2
• Power leads L2 and L3
• Power leads L3 and L1
Single Phase Motors
Touch one voltmeter lead to each of the lines supplying
power to the pump L1 and L2, (or L1 and N for 11SV circuits).
Preliminary Checks
Supply Voltage
To check the voltage being supplied to the motor, use a voltmeter. Be careful, since
power is still being supplied to the pump. Do not touch the voltmeter leads together
while they are in contact with the power lines.
Evaluation
When the motor is under load, the voltage should be within
10%
(+
or -) of the
nameplate voltage. Anyvariation larger than this may indicate a poor electrical supply
and can cause damage to the motor windings. The motor should not be operated
underthese conditions. Contact your power supplierto correct the problem or change
the motor to one requiring the voltage you are receiving.
Current Measurement
To check the current, use an ammeter. To do so, fCmuw these steps:
1. Make sure the pump is operating
2.
Set the ammeter to the proper scale.
3. Place the tongs of the ammeter around the leg to be measured.
4.
Compare the results with the amp draw information on
the motor nameplate.
S.
Repeat for the other legs.
Evaluation
If the current draw exceeds the listed nameplate amps, or if
the current imbalance is greaterthan
5%
between each leg on
three phase units, then check the following:
• The voltage supplied to the pump maybe too high or too
low.
o
The contacts on the motor starter may be burned.
o
The terminals in the starter or terminal box may be
loose.
• There may be a Winding defect. Check the Winding and
insulation resistance
• The motor windings may be shorted or grounded.
Fig.19
C::=::::J
Page 11
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