Electric friction clutch drive

In the electric friction clutch drive, there is no direct mechanical connection between input and output shaft, eliminating mechanical friction and wear. Electrical forces are used to engage the input and output shaft. The three main types are hysteresis, eddy-current, and magnetic particle clutches. In the extrusion industry, the eddy-current drive has been widely applied in the past. The majority of the older extruders were equipped with eddy-current drives. [Pg.50]

The popularity of this drive was, and still is to a large extent, due to the simplicity of the drive. In simple terms, the eddy-current drive consists of a fixed speed AC motor driving a steel drum see Fig. 3.1. [Pg.50]

Inside this drum, a wire-wound rotor is positioned, with a small annular gap between rotor and drum. When a low-level current is applied to the rotor, it is dragged by the rotation of the drum at a somewhat lower rotational speed. When the voltage to the rotor is reduced, the slippage between the rotor and drum will increase. Thus, reduced voltage reduces the rotor speed, since the speed of the drum is constant. By controlling the voltage to the rotor, the rotor speed can be varied or it can be maintained at a steady speed under varying loads. [Pg.51]

Typical operating characteristics for eddy-current drives are [3] [Pg.51]

The efficiency of the eddy-current drive is proportional to the difference between input and output speed. Thus, when an extruder is operated at low speeds for extended periods of time the eddy-current drive would not be a good candidate from an energy consumption point of view. It is possible to reduce this problem by using a two-speed AC motor to drive the eddy-current clutch [3,4]. [Pg.51]

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