Stator - 120 V - Husqvarna K 3000-Electric Workshop Manual

1
mH
A
B
STATOR – 120 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 cover to the carbon brushes.
Break the electric circuit to the rotor by pulling out both the carbon brushes
a little and lock with the spring to the side. Connect one of the test pins to the
carbon brush's cable on the left side.
Disconnect the contact to the stator (grey cable) at the circuit board and
connect to the other test pin.
Measured values
Typical measured values for a correct stator are around 10–12 mH. Typical
Ω
value for resistance measurement is around 0.2–0.3 ohm.
If the stator winding is fractured you get the value 0 mH. Resistance
measurement gives a maximum, or immeasurable ohm figure.
Short-circuited winding turns reduce the inductance value. If the value is
30 % (around 7 mH) 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 the flat pin sleeve (A) and one of
the ring cable lugs (B). Repeat the measurement on the other ring cable lug.
Typical values for a winding (one of two) are for an inductance measure-
ment 4–4.5 mH and for a resistance measurement 0.5–0.6 ohm. Major devia-
tions between the windings indicate a defect stator.
B
13
15