Electric cluches are used to :
- Engage very large motors to their loads after the motor have reached running speeds.
- Provide smooth starts for operations in which the material being processed might be damage by abrupt starts.
- Start high- inertia loads when starting may be difficult for motor that is sized to handle only the running load.
In general an electric clutch consists of an electromagnet
disc and an armature disc. When disengaged, the clutch couples the two
together, allowing both to rotate. A magnetic field is generated as soon as
current flows through the electromagnet disc. This draws the armature disc into
direct contact with the magnet. The
electromagnet disc is faced with friction material to provide positive
engagement between the two discs. Engage and disengage motions are signaled by a
switch or sensor.
The electric clutch serves two functions in the operation of
the mower. In addition to starting and stopping the power flow to the cutter
blades, the clutch also acts as a brake to assist in stopping blade rotation
when the PTO is switched off. When energized, the magnetic coil in the clutch
pulls the armature into contact with the rotor, which is attached to the engine
crankshaft. The armature begins to rotate, turning the attached pulley, to
drive the mower blades.
When the voltage is turned off, the magnet releases the
armature. The armature is pulled against the brake cover by the armature
springs. The pulley is quickly stopped by the brake, stopping the rotation of
the mower blades. When a machine is new or after a clutch has been replaced, it
needs to be burnished. Burnishing the clutch helps mate the surfaces of the
rotor and armature. When burnishing a clutch, the engine should be run at ¾
throttle. Then engage and disengage the PTO switch approximately 50 times.
Never perform the burnishing procedure while cutting grass.
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