Method and apparatus for an emergency lowering kit

摘要

A method and apparatus are disclosed for lowering a load on a direct current hoist motor during an electrical power interruption, the method including but not limited to determining in a crane processor that the electrical power interruption has occurred; and providing a brake assist current to shunt field on the direct current hoist motor to produce a counter torque in the hoist motor.

主权项

1. A method for lowering a load on a direct current hoist motor during an electrical power interruption to the direct current hoist motor, the method comprising:
determining in a crane processor that an electrical power interruption to the direct current hoist motor has occurred; and providing a brake assist current to a shunt field on the direct current hoist motor to produce a counter torque in the direct current hoist motor; electrically connecting a variable resistance brake assist resistor in series with a dc power supply and the shunt field wherein a brake assist resistance value for the variable resistance brake assist resistor is controlled by the crane processor; and varying the brake assist resistance value proportionately to a measured hoist hook speed to proportionately increase the brake assist value to proportionately provide counter torque with an increase in hoist hook speed.