Electromagnetic Clutch - Stiga MPV 320W Workshop Manual

WORKSHOP MANUAL Chapter EDITION PAGE
MPV 320W / 520W 7 - ELECTRICAL SYSTEM 2017 60 /
64
To check a diode, isolate if from the circuit by disconnecting one end. With a multitester set on the
lowest ohms scale setting, measure the resistance in one direction, reverse the test leads, and
measure in the other direction.
Readings should be high in one direction and low in the other.
• If the readings are the same in both directions, the diode has short-circuited.
• If the readings are high, the diode is open.
• If the readings are the same in both directions, the diode is faulty and must be replaced.
IMPORTANT - Diodes are marked to indicate polarity (a band on one end, an arrow on the side,
or they fit on a holder only one way to prevent inverting the polarity.
• Rectifiers - The battery is charged via an alternator on the engine. A charging circuit contains a
rectifier because alternators produce alternating current (AC) and batteries require direct current
(DC) for charging.
The rectifier may be built into the engine or it may be an external component. It may also contain
a regulator to prevent overcharging the battery.
NOTE - The repair of rectifiers integrated in the engine must be performed by a service centre
authorised by the engine manufacturer, which has access to the information and parts needed for
the checks and repairs.

7.2.9 Electromagnetic clutch

The electromagnetic clutch is used to connect or disconnect, via a switch, the equipment used on
the machine. In addition, the clutch is designed to activate a brake on the output shaft, when it is
disengaged.
The field coil is mounted to a bearing support and does not rotate.
The rotor is attached to the power output shaft and rotates around the field assembly.
The armature is connected to the output pulley.
The armature unit is assembled close to the brake unit rotor. The clutch is engaged by applying
current to the coil connection.
This results in a current flowing through the coil,
magnetizing the coil pulling the armature onto the
rotor with sufficient force to hold the two pieces
together, connecting the output and the input
shafts firmly together.
The force of the armature against the rotor pulls it
away from the brake, hence releasing the brake.
To adjust it, follow the " Setting the electromag-
netic clutch air gap" [ 6.2.9].