14
STATOR – 230 V
Functional test
Fractures to the stator winding are easiest to indicate using the check below.
In general, short-circuited windings can also be identified, particularly if the
short circuit eliminates current in several winding turns. If the short circuit
only eliminates a few turns, the measurement is unlikely to record this. A
fault like this has no noticeable effect on the performance of the motor either.
Resistance measurement – Ohm (Ω)
Resistance measurement provides an unequivocal answer as to whether the
stator winding is fractured. However, the method gives unclear indications for
short-circuited winding turns.
Inductance measurement – Henry (H)
The dimension is “Henry”, abbreviated H (1H = 1000 mH). Inductance
measurement is best applied to both identify fractures in the stator winding or
short-circuited winding turns.
Use short measuring cables and lay these close to each other: the easiest way
is to twist them. Cables run in a coiled way give incorrect readings.
Preparations, illustration 1
Remove the inspection covers for the carbon brushes and right handle half,
see “Wiring diagram, cabling” chapter, page 8.
The stator winding is divided at the circuit board and is connected in the
following way: Pull out the contacts to the stator at the circuit board. Connect
the contacts using a cable fitted with flat pin contacts.
Preparations, illustration 2
You do not need to remove the carbon brushes. Lift these up and lock with the
spring to the side. Connect the test pins to the cables on the carbon brushes.
Measured values
Typical measured values for a correct stator is 40 mH. Resistance measurement
gives around 0.8 ohm.
If the stator winding is fractured you get the value 0 mH. Resistance measure-
ment gives a maximum, or immeasurable ohm figure.
Short-circuited winding turns reduce the inductance value. If the value is
30 % (around 30 mH) below the typical value, the stator is unfit for use.
mH
Ω
1
2
12
A dismantled stator is best tested by measuring both stator windings indivi -
dually. Connect the measurement cables to one of the winding's flat pin sleeve
(A) and ring cable lug (B). Repeat the measurement on the other winding (A/B).
Typical values for a winding (one of two) is 2.8 mH and 0.4 ohm. Major
deviations between the windings indicate a defect stator.
B
A
A
B
