Electromagnetic Clutch Working, Applications, Advantages and Disadvantages

Electromagnetic_clutch_image
The operating principle of the actuator of electromagnetic clutch is an electromagnetic effect, but torque transmission is mechanical. The difference between electromagnetic clutch and the regular clutch is in how they control the movement of pressure plates. In the normal clutch, a spring used to engage the clutch whereas in EM clutch an electromagnetic field is used for engagement.

The electromagnetic clutch comes various forms, including magnetic particle clutch and multi-disc clutch. There are even no-contact clutches such as hysteresis clutch and eddy current clutch. However, most widely used form is single face friction clutch.

Working of electromagnetic clutch

The main components of EM clutch are a coil shell, an armature, rotor, and hub. The armature plate is lined with friction coating. The coil is placed behind the rotor. When the clutch activated the electric circuit energizes the coil, it generates a magnetic field. The rotor portion of clutch gets magnetized. When the magnetic field exceeds the air gap between rotor and armature and then it pulls the armature toward the rotor. The frictional force generated at the contact surface transfer the torque. Engagement time depends on the strength of magnetic fields, inertia, and air gap.
When voltage is removed from the coil, the contact is gone. In most design a spring is used to hold back the armature to provide an air gap when current is removed.

Application of electromagnetic clutch

They can be used for remote application because they do not require linkage to actuate the clutch. They are used in printing machinery, conveyor drives, copier machines and factory automation. In an automobile, it replaces clutch pedal by a simple switch button. A smaller EM clutch is used to drive the compressor of air conditioning system.

Advantage and disadvantage of electromagnetic clutch

Advantage
  • The complicated linkage is not required to control clutch.
Disadvantage
  • High initial cost.
  • Operating temperature is limited because at high-temperature insulation of the electromagnet gets damaged.
  • The risk of overheating during the engagement.
  • The brushes used to energize coils are needed a periodic check.

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