Checking Of Motor And Cable - Andritz SU8 Serie Instructions De Service

Series SU8

6.1.Checking of motor and cable

1. Supply voltage Measure the voltage between the phases
by means of a voltmeter.
On single-phase motors, measure
between phase and neutral or between
two phases, depending on the type of
supply.
Connect the voltmeter to the terminals in
the motor starter.
2. Current Measure the amps of each phase while
consumption the pump is operating at a constant
discharge head (if possible, at the
capacity where the motor is most heavily
loaded).
For maximum operating current, see
nameplate.
Items 3 and 4: Measurement is not necessary when the supply voltage and the current consumption are normal.
3. Winding Disconnect the submersible drop cable at
resistance the motor starter.
Measure the winding resistance between
the leads of the drop cable.
4. Insulation Disconnect the submersible drop cable at
resistance the motor starter.
Measure the insulation resistance from
each phase to earth (frame).
Make sure that the earth connection is
made carefully.
The voltage should, when the motor is loaded, be within the
specified range. The motor may burn if there are larger
variations in voltage. Large variations in voltage indicate poor
electricity supply, and the pump should be stopped until the
defect has been remedied.
On three-phase motors, the difference between the current in
the phase with the highest consumption and the current in the
phase with the lowest consumption should not exceed 5 %.
If so, or if the current exceeds the full load current, there are the
following possible faults:
• The contacts of the motor starter burnt. Replace the contacts
or the control box for single-phase operation.
• Poor connection in leads, possibly in the cable joint. See item
3.
• Too high or too low supply voltage. See item 1.
• The motor windings are short-circuited or partly disjointed.
See item 3.
• Damaged pump is causing the motor to be overloaded. Pull
out the pump for overhaul.
• The resistance value of the motor windings deviates too much
(three-phase). Move the phases in phase order to a more
uniform load. If this does hot help, see item 3.
For three-phase motors, the deviation between the highest and
the lowest value should not exceed 5 %.
If the deviation is higher, pull out the pump.
Measure motor, motor cable and drop cable separately, and
repair/replace defective parts.
Note: On single-phase, 3-wire motors, the operating winding
will assume the lowest resistance value.
If the insulation resistance is less than 0,5 MΩ, the pump
should be pulled out for motor or cable repair.
Local regulations may specify other values for the insulation
resistance.
Table 3: Checking of motor and cable
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