Stator - 230 V - Husqvarna DM 330 Workshop Manual

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1
2
mH
20
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 (1 H = 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, figure 1
Remove the inspection cover to the carbon brushes.
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.
Testing, figure 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.
Measurement values DM330 and DM340
Typical measurement values for a full stator are 40 mH for DM330 and
45 mH for DM340. Resistance measurement gives around 0.8 ohm and
0.9 ohm respectively.
If the stator winding is fractured you get the value 0 mH. Resistance measu-
Ω
rement gives a maximum, or immeasurable ohm figure.
Short-circuited winding turns reduce the inductance value. If the value is
30 % below the typical value, the stator is unfit for use.
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
sleeves and ring cable lugs. Repeat the measurement on the other winding.
Typical values for a winding (one of two) are for DM330/DM340: 2.8/3.0 mH
and 0.4/0.3 ohm respectively. Major deviations between the windings indicate
a defect stator.
Dismantling
Loosen the contacts.
Remove both stator screws.
Pull the stator out of the motor
housing.
Dismantling
Loosen both the flat pin contacts from
the circuit board.
Remove the two screws that hold the
stator in the motor housing.
Pull the stator out of the motor housing
by hand.
The round cable lugs are the connec-
tions to the carbon brushes. The flat pin
contacts are the connections to the
circuit board.
525 59 31-26