Goulds Pumps VS - IOM - Manual (Page 23)

15
Resistance measured between the power cable
leads after splicing the power cable to the motor
leads will indicate the resistance of the power
cable plus the motor windings. The motor winding
resistance is obtained by the formula below. The
calculated value should be within the limits speci-
fied in the motor manual.
Motor Winding = Reading taken - Cable resistance
Resistance
= at Power Cable - from Table 2
A higher winding resistance than shown in the
motor manual indicates a possible burned (open)
winding, an open cable, a loose connection, or the
wrong motor (different HP or voltage than readings
being referenced).
A considerably lower winding resistance than
shown in the motor manual indicates a possible
shorted (burned together) winding or the wrong
motor.
Unequal resistance between the windings on a
three phase motor indicates a burned winding or a
faulty connection.
TABLE C. 1 – NORMAL INSULATION RESISTANCE VALUES BETWEEN ALL LEGS AND GROUND
Insulation resistance does not vary with rating. Motors of all HP, voltage, and phase rating have the same
insulation resistance ranges.
METER READING
R x 100K R x 10K
CONDITION OF MOTORS AND LEADS OHMS MEGOHMS or or
R x 100,000 R x 10,000
Scale Scale
BENCH TESTS
• A new motor (without drop cable). 20,000,000 + 20+ 200+ 2000 + or 2K +
• A used motor which can be reinstalled 10,000,000 + 10+ 100+ 1000 + or 1 K +
in the well.
• Cable splice after immersion for one 2,000,000+ 2+ 20+ 200+
hour in water.
WELL TESTS Ohm readings are for drop
cable plus motor.
• A new motor or used motor in good 2,000,000+ 2+ 20+ 200+
condition.
• A motor in reasonably good condition. 500,000- 0.5-2.0 5-20 50-200
2,000,000
• A motor which may have been
damaged by lightning or with 0.02-0.5 0.2-5 2-50
damaged leads. Do not pull the pump 20,000-500,000
for this reason.
• A motor which definitely has been
damaged or with damaged cable. 0.01-0.02 0.1-0.2 1-2
The pump should be pulled and 10,000-20,000
repairs made to the cable or the motor
replaced. The motor will not fail for
this reason alone, but will probably
not operate for long.
• A motor which has failed or with
completely destroyed cable insulation. 0-0.01 0-0.1 0-1
The pump must be pulled and the Less than 10,000
cable repaired or the motor replaced.
+ Indicates that the reading should be the value shown or greater. Higher readings indicate better insulation.