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Control of Magnetic Clutch Disclosure Number: IPCOM000092816D
Original Publication Date: 1967-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 39K

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Related People

Padalino, M: AUTHOR [+1]


This circuit controls the performance of a magnetic clutch under very stringent time requirements.

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Control of Magnetic Clutch

This circuit controls the performance of a magnetic clutch under very stringent time requirements.

A gate signal establishes when the clutch is to be engaged or disengaged. This signal sets a trigger to the on condition thus enabling driver 1. At the same time the signal turns on driver 2. Transistor T1 supplies a pickup current to the clutch at a rate defined by the time constant T = L(off)/(R1 + R4). Loff is the inductance of the clutch coil when the armature is disengaged. In order to improve the time performance of the device, the current through T1 tends toward an asymptote in excess of the value tolerated by the clutch. If this current is allowed to reach its final value, the clutch can be damaged or the magnetic material can be saturated. Both events are undesirable. To prevent this condition, resistor R4 is used to produce a voltage proportional to idL/dt. The change of inductance taking place while the clutch is engaged is represented by dL. The detection of the negative slope of the current waveform is used to turn off the trigger and hence T1. The time to turn on the clutch is given by

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where i(th) represents the pickup current of the device.

When T1 is turned off, T2 supplies the hold cur rent required to maintain the clutch engaged. When the gate signal is turned off, driver 2 is de-energized and the hold current is reduced below the threshold value i'(th). At such point the clutch is disengaged at a rate def...