On the issue of dynamic braking as applied to a mine hoist with an asynchronous drive

Abstract

In practice, it may be necessary to lower people down a mine shaft at a reduced speed compared to the full speed of lifting the load. This makes it necessary to use braking operations, which in practice are often carried out using a mechanical brake. However, prolonged operation of a mechanical brake is accompanied by undesirable phenomena: excessive heating and wear of the brake pads, which necessitates the use of cooling devices and frequent replacement of worn pads with new ones. Electric braking systems are free from these drawbacks, of which in the case under consideration both counter-current (counter-switching) and dynamic braking can be used. To be able to implement the counter-current mode, the lifting unit must be equipped with a load rheostat, which, compared to an ordinary starting rheostat, must be designed for longer operation. In addition, this rheostat must have additional sections with a correspondingly increased resistance to be able to obtain small braking moments. The main disadvantage of counter-current braking is its uneconomical nature, due to the significant consumption of energy from the network. As is known, the power consumed in the counter-current mode from the network depends on the magnitude of the braking torque and synchronous speed and does not depend on the actual speed of descent. The energy consumed from the network is inversely related to the speed of descent.