Stator - Husqvarna DM 230 Workshop Manual

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STATOR

Functional test
Breaks in the stator winding are easily identified by carrying out the functional
test described below. In general, short-circuited windings can also be identified,
particularly if the short circuit excludes current in several winding turns. If
the short circuit only excludes a few turns, the measurement is unlikely to
record this. A fault like this has hardly any noticeable effect on the perfor-
mance of the motor either.
Resistance measurement – Ohm (Ω )
Resistance measurement provides an unequivocal answer as to whether the
stator winding is broken. 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 breaks in the stator winding or
short-circuited winding turns.
Preparations, illustration 1
Remove the inspection cover to the carbon brushes.
The stator winding is divided at the circuit board and connected in the follow -
ing way: Disconnect the contacts to the stator, i.e. contacts 2 and 3 as shown on
page 15. Connect the contacts using a cable fitted with flat pin contacts.
Test cables – inductance measurement
Use short test cables and lay these close to each other: the easiest way is to
twist them. Cables run in a coiled way give incorrect readings.
Testing – inductance measurement, illustration 2
You do not need to remove the carbon brushes. Lift these up and lock with the
spring. Connect the test pins to the cables on the carbon brushes.
Measured values
Typical measured values for a complete stator is around 60 mH. Typical value
for resistance measurement is around 1.6 ohm.
If the stator winding is broken 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 falls
below 45 mH, the stator is unusable.
A dismantled stator measured without enclosed rotor produces around 9 mH.
If the value falls below 6 mH, the stator is defective.
Ω
IMPORTANT! When measuring inductance it is particularly important
that no large iron or steel objects are present in the immediate vicinity. If, for
example, the stator is placed on a steel covered work bench, you will get
unusable measured values.
Dismantling
Remove the carbon brushes and
the screws to the cable lugs.
Remove both stator screws.
Pull the stator out of the motor
housing.
Dismantling
Remove the carbon brushes and the
screws to the cable lugs.
Remove the two screws that hold the
stator in the motor housing.
Pull the stator out of the motor housing
by hand.
Reassembly
The round cable lugs are the connections
at the carbon brushes. The flat pin con-
tacts are connected to the circuit board,
position 2 and 3 on page 15.