GB1004819A - Magnetic clutch coolant control - Google Patents

Abstract

1,004,819. Correspondence control. LOUIS ALLIS CO. Feb. 12,1964 [Feb. 21,1963], No. 5853/64. Heading G1N. Fluid cooling of a magnetic clutch is controlled by varying the rate of flow of coolant in dependence upon an electrical signal indicative of the instantaneous rate of heat generation in the clutch. The horse power loss in the clutch is indicative of the rate of heat generation. Inductor drum 20 of the clutch is driven by induction motor 11, and clutch rotor 21 drives load 12. The current supplied to field coil 25 on rotor 21 controls the output speed and torque of the clutch. A voltage indicative of this current is derived at 55 and applied to multiplier 60, e.g. a Hall device. A tachogenerator 41 on the clutch output shaft 13 provides a signal indicative of the output speed and from this signal, after rectification, is subtracted a reference voltage representative of the speed of induction motor 11. The difference represents the slip in the clutch and is also applied to multiplier 60. The product is stated to be proportional to the rate of heat generation. This signal is balanced against a reference value from battery 66 and the difference actuates either relay 68 or 69, depending on the polarity. As a result a motor 36 is driven to open or close a valve 35 controlling the flow of coolant to jacket 30 surrounding the clutch. In a modification a signal proportional to the horse power input to the clutch is supplied to the multiplier, instead of the clutch field current. A transformer is inserted in one of the input lines to induction motor 11 and the rectified secondary current is supplied to the multiplier. It is stated that the resultant product is also proportional to the horse power loss in the clutch. Instead of tachogenerator 41 a slip generator may be mounted on the output shaft of the clutch. This consists of a three phase rotor and a twelve phase stator, the stator windings being connected through rectifiers to a common positive output terminal, while the other ends of the windings are commonly connected to a negative terminal. The terminals are interconnected by a smoothing capacitor. The rotor is energized from the same source as driving motor 11 and is mounted so that it rotates in the opposite direction to the rotating field which it generates. At non- synchronous speeds an output is produced which is indicative of the continued slip of induction motor 11 and the clutch. A voltage representative of the slip of the induction motor is subtracted. Where wide variation in the rate of heat generation is likely, valve operating motor 36 may also drive the slider of potentiometer 67.