Husqvarna DM 650 Workshop Manual page 17

MOTOR
Function
Working method
The way in which the high frequency motor works differs
significantly from a traditional motor with rotor windings and
collector/carbon brushes.
The rotor in the high frequency motor consists of permanent
magnets with a high magnetic force, known as neodymium mag-
nets. The rotor therefore has no windings and electrical compo-
nents.
The stator has several field windings. The high frequency unit,
which is connected to the motor, generates a rotating magnetic
field in the stator and the rotor follows this movement.
In comparison with the traditional motor, the rotor and stator
have essentially swapped functions.
The high frequency motor is considerably more efficient than a
carbon brush motor and its output, in relation to its weight, is sig-
nificantly higher, which is why it is ideal for hand-held machines.
Cooling
The cavity between the stator and the rotor is filled with oil. This
oil leads and distributes the heat out towards the motor housing.
An outer jacket surrounds the motor housing and the space has
channels for cooling water. The photo below shows the structure of
the motor housing and cooling jacket.
The water is first directed through the motor and then on to the
spindle shaft and the drill. The machine must not be operated
without water cooling.
Testing in the workshop
Water does not need to be connected for motor cooling for short-
term testing with the motor without load.
Service actions
The motor will probably not require any service actions during
the service life of the machine. Repairs to this type of motor are
complicated and require both special knowledge and special tools,
and this work is not really of a type which can be carried out at a
regular service workshop. Therefore, a failed motor will be replaced
by a complete new motor.
Rotor
The rotor has permanent magnets of neodymium and therefore has
no electrical components such as windings and carbon brushes.
The gear wheel that drives the primary shaft in the gear housing is
attached to the shaft through shrinking. The gear wheel cannot be
replaced separately.
Thyristor
The thyristor is the motor's temperature sensor and is an integral
part of the motor. The thyristor cannot be replaced separately.
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