GB1058284A - A control system for electric motors - Google Patents

Abstract

1,058,284. Commutating arrangements for dynamo electric machines. GOLAY BUCHEL & CIE S.A. Jan. 31, 1964 [Jan. 31, 1963; Aug. 24, 1963], No. 4311/64. Heading H2A. A motor has a rotor and a stator winding which is energized through a first switching device which operates in accordance with rotor position and a second switching device which operates when an electrical parameter exceeds a set value to over-ride the first switching device and cut off the current supply to the motor winding. As shown, the supply to winding M is controlled by transistor switches 1, 2 which are controlled by rotor position detectors 7, 8. Detectors 7, 8 are controlled by the bi-stable trigger circuit comprising normally conductive transistors 3, 5 for the two directions of current flow in the winding respectively. If, however, the current in winding M rises, the voltage developed across resistor R will rise to a level that changes the trigger circuit to its other stable state thus rendering transistors 3, 5 non-conductive and thereby switching off the supply to detectors 7, 8. When the current falls to a set level control will be restored to detectors 7, 8 by transistors 3, 5 once again becoming conductive. Resistors R, R 1 and R 2 are chosen to give the required upper and lower limit values and this circuit may be used to control the speed of the motor. The diodes 9, 10 are employed, in the normal way, to recover the inductive energy stored in winding M. In a modification two motor windings having high mutual inductance are used and the limit values are set by capacitor 25 and potentiometer 18, Fig. 4 (not shown). A second set of motor windings whose energization is controlled in a similar way may be used. In a further modification the switching transistors are bridge connected with the motor winding connected in one arm of the bridge. Diagonal pairs of transistors are controlled together through a transformer coupling and in one case, Fig 5 (not shown), a low control voltage is used but in a second case, Fig. 6 (not shown), the connection is such that a control voltage is not needed. The limit values are set by resistors 44, 49, potentiometer 46 and diode 45 in the Fig. 5 connection and resistors 60, 61 in Fig. 6. It is stated that the motor may be braked by reversal of the polarity of the switching device and that a magnetically saturable circuit element or multivibrator can be used.