B - Operations – Transporting – 66 – B
Patent
B - Operations, Transporting
66
B
364/34
B66B 1/30 (2006.01) H02M 7/162 (2006.01) H02P 7/28 (2006.01)
Patent
CA 1130482
Case 2609 MINE HOIST DRIVE ABSTRACT OF THE DISCLOSURE A friction-type mine hoist drive has at least one d.c. motor to drive the hoist. Two six pulse converters are connected in series to provide d.c. power for the motor. A free-wheeling diode is connec- ted across the output of one converter. A control uses a first one of the converters (without the free- wheeling diode) to provide power for the hoist for the first 50% of the speed range and then phases on the second of the converters to add power from 50% to substantially 100% speed. While there is no kvar reduction in the first converter the kvar demand is less than 50% of conventional back to back converter, and the free-wheeling diode across the second converter reduces kvar demand and reduces ripple when the second converter is operating. There is little requirement for fourth quadrant operation because deceleration is normally taken care of by gravity. However the possibility of fourth quadrant operation may be handled in several ways. First, a load value is determined for a particular hoist representing the dividing point between inversion being required and not required when decelerating from full speed. By measuring speed and current when the hoist begins operation, the actual load is determined and the actual load compared with the predetermined load value. If inversion might be required when decelerating from full speed, the hoist can be limited to half speed by locking out the second converter and operating with the first converter. As one alternative the first converter can handle the requirement for inversion by operating in the fourth quadrant when required. As another alternative, a switch can be provided in series with the free-wheeling diode to remove it from continued......... Case 2609 ABSTRACT OF THE DISCLOSURE (continued) the circuit to make both the first and second converters available for fourth quadrant operation.
325421
Eastcott Peter Deh.
Young John A.i.
Canadian General Electric Company Limited
Eckersley Raymond A.
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