Grundfos MS Series - Current Consumption Measurement; Winding Resistance Measurement

English (GB)
23
2. Current
consumption
TM00 1372 5092
Measure the amps of each
phase while 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.
For the MS6000P, the
current consumption must be
measured between the sine
wave filter and the motor.
On three-phase motors, the difference between the
current in the phase with the highest consumption
and that with the lowest consumption must not
exceed 5 %. Otherwise, or if the current exceeds the
rated current, the following faults may occur:
• The contacts of the motor-protective circuit
breaker burn.
– Replace the contacts or the control box for
single-phase operation.
• There is poor connection in leads, possibly in the
cable joint.
– See item 3.
• The mains voltage is too low or too high.
– 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 assembly for overhaul.
• The resistance value of the motor windings
deviates too much (three-phase operation).
– 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 the current consumption are
normal.
3. Winding
resistance
TM00 1373 5092
Disconnect the submersible
drop cable from the motor-
protective circuit breaker or
sine wave filter. Measure the
winding resistance between
the leads of the drop cable.
Three-phase motors: The deviation between the
highest and lowest value must not exceed 10 %. If
the deviation is higher, pull out the pump assembly.
Measure motor, motor cable and drop cable
separately, and repair/replace the defective parts.
Note: On single-phase, 3-wire motors, the operating
winding will assume the lowest resistance value.