Electromagnetic Clutch Research Paper

ELECTROMAGNETIC CLUTCH
An electromagnetic clutch is a clutch which operate electrically but transmit torque mechanically and is engaged and disengaged by an electromagnetic actuator.
The electromagnetic clutch is most suitable for remote operation since no linkages are required to control its engagement. It has fast and smooth operation. But because of its energy dissipation as heat in the electromagnetic actuator every time the clutch is engaged, there is a risk of overheating. Consequently the maximum operating temperature of the clutch is limited by the temperature rating of the insulation of the electromagnet. This is a major limitation. Another disadvantage is higher initial cost.
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These clutches can be used for both dry and wet. The heat dissipation capability could be increased by running the clutches in an oil bath, which makes them ideally suited for multiple speed gear boxes and machine tool applications.
Multiple disk clutches operates through an electrical actuation but transmit torque mechanically. When current is passed through the clutch coil, the coil act as an electromagnet and it produces magnetic flux lines. These lines of flux are transferred through the small air gap between the field and the rotor. The rotor portion of the clutch becomes magnetized and sets up a magnetic loop, which attracts both the armature and friction disks. The attraction of the armature squeezes the friction disks and transfer the torque from the inner driver to the out disks. The clutch slips until the input and output RPMs are same. The output disks are connected to a gear or pulley via drive cup. When the current is removed from the clutch, the armature is free to turn with the shaft. Springs holds the friction disks away from each other, so that there is no contact when the clutch is not engaged, creating a minimal amount of

Engagement
Whenever the clutch is required to actuate, voltage/current is applied to electromagnet, in return produces magnetic field. The rotor portion of the clutch becomes magnetized and sets up a magnetic loop which attracts the armature. The armature is pulled against the rotor and a frictional force is generated at contact. Within a relatively short time, the load is accelerated to match up the speed of the rotor, thereby engaging with the armature and the output hub of the clutch. In most cases, the rotor is constantly rotating with the input all the time.
Disengagement
When current/voltage is removed from the clutch, the armature is free to turn with the shaft. In most of the designs, springs hold the armature away from the rotor surface when power is released, creating a small air gap.
Cycling
Cycling is achieved by turning the voltage/current to the electromagnet on and off. Slippage normally occurs only during acceleration. When the clutch is fully engaged, there is no relative slip, assuming the clutch is sized properly, and thus torque transfer is 100% efficient.