The driver operates the switch by holding the gear lever to change the gear, thus cutting off current to the electromagnet and disengaging the clutch. When the electromagnetic clutch is used in automobiles, there may be a clutch release switch inside the gear lever. Other applications include packaging machinery, printing machinery, food processing machinery, and factory automation. This type of clutch is used in some lawnmowers, copy machines, and conveyor drives. When the clutch is fully engaged, there is no relative slip, assuming the clutch is sized properly, and thus torque transfer is 100% efficient. Slippage normally occurs only during acceleration. In most designs, springs hold the armature away from the rotor surface when power is released, creating a small air gap.Ĭycling is achieved by interrupting the current through the electromagnet. When current is removed from the clutch, the armature is free to turn with the shaft. In most instances, the rotor is constantly rotating with the input all the time. Within a relatively short time, the load is accelerated to match the speed of the rotor, thereby engaging the armature and the output hub of the clutch. The armature is pulled against the rotor and a frictional force is generated at contact. The rotor portion of the clutch becomes magnetized and sets up a magnetic loop that attracts the armature. When the clutch is actuated, current flows through the electromagnet producing a magnetic field. Another disadvantage is higher initial cost. Consequently, the maximum operating temperature of the clutch is limited by the temperature rating of the insulation of the electromagnet. However, because the activation energy dissipates as heat in the electromagnetic actuator when the clutch is engaged, there is a risk of overheating. Single-face clutches make up approximately 90% of all electromagnetic clutch sales.Įlectromagnetic clutches are most suitable for remote operation since no mechanical linkages are required to control their engagement, providing fast, smooth operation. Since the clutches started becoming popular over 60 years ago, the variety of applications and clutch designs has increased dramatically, but the basic operation remains the same today. Over the years, EM became known as electromagnetic versus electro-mechanical, referring more about their actuation method versus physical operation. This is why they used to be referred to as electro-mechanical clutches.

Electromagnetic clutches operate electrically but transmit torque mechanically.

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