Grundfos MS6000, Инструкция по эксплуатации, Страница: 16 / 25

English (GB)
16
1. Checking the motor and cable
1. Supply voltage
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Measure the voltage between the
phases by means of a voltmeter.
Measure on the terminals where
the submersible drop cable is
connected. When the motor is loaded, the voltage should be within the
required voltage quality for Grundfos MS submersible
motors which,measured at the motor terminals,is - 10 %/+
6 % of the rated voltage for continuous operation
(including variation in the supply voltage and losses in
cables).
Check also that there is voltage symmetry in the power
supply lines, i.e. the same difference of voltage between
the individual phases.
Large variations in voltage may cause the motor to burn.
Large variations in voltage indicate poor power supply, and
the motor must be stopped until the defect has been
remedied.
2. Current consumption
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Measure the current of each
phase while the pump is
operating at a constant
discharge pressure (if possible,
at the capacity where the motor
is most heavily loaded). For
maximum operating current, see
nameplate. On three-phase motors, the difference between the current
in the phase with the highest current consumption and the
current in the phase with the lowest current consumption
must not exceed 5 %. If so, or if the current exceeds the
maximum operating current, there are the following
possible faults:
• The contacts of the motor-protective circuit breaker are
burnt.
– Replace the contacts or the control box for
single-phase operation.
• Poor connection of conductors, 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 not help, see item 3.
Items 3 and 4: Measurement is not necessary when the supply voltage and current consumption are normal.
3. Winding resistance
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Disconnect the submersible drop
cable at the motor-protective
circuit breaker. Measure the
winding resistance between the
conductors of the submersible
drop cable. See section
2. Winding resistances .
Note: Include the resistance of
the submersible drop cable. See
section
2.3 Resistance values for
cables .
For three-phase motors, the difference between the
highest and lowest winding resistance must not exceed 10
%. If the deviation is higher, pull out the motor. Measure
motor, motor cable and submersible drop cable separately,
and repair/replace defective parts.
4. Insulation resistance
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Disconnect the submersible drop
cable at the motor-protective
circuit breaker. Measure the
insulation resistance from each
phase to earth (frame). Make
sure that the earth connection is
made carefully. If the insulation resistance deviates from the values in
section
1.1 Insulation resistance , the motor should be
pulled out for motor or cable repair. Local regulations may
stipulate other values of insulation resistance.