Motor drive system for an electric mining shovel
First Claim
1. In a drive system for a mining machine having a hoist motor, a crowd motor and a swing motor, the combination comprising:
- a rectifier circuit having inputs connected through lines to a source of a.c. power and an output terminal at which d.c. power is produced;
disconnect means connected to said lines and being operable in response to a disable signal applied to a power enable input to disconnect said rectifier circuit from said a.c. power source;
a d.c. bus connected to said rectifier output terminal;
a set of inverters, each having an input connected to said d.c. bus, each having an output connected to one of said motors and each being operable in response to signals from an associated inverter control circuit to deliver power to its attached motor from said d.c. bus and to regenerate power to said d.c. bus from its attached motor; and
a power monitor and control circuit which includes;
a. voltage sensing means coupled to said a.c. power source for generating an analog signal which is proportional to the voltage applied to the inputs of said rectifier circuit;
b. comparator means connected to said voltage sensing means for generating a preselected logic signal when said analog signal drops below a predetermined level;
c. timer means connected to said comparator means and being enabled by said preselected logic signal to generate said disable signal to said disconnect means power enable input when said preselected logic signal is present for a preselected time interval; and
d. means connected to said d.c. bus for generating a reduction signal to each of said inverter control circuits which reduces the power delivered by said inverters to their attached motors when the voltage of said d.c. bus drops below a preselected level.
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Accused Products
Abstract
A motor drive system for a mining shovel includes three a.c. motors which are driven by associated inverter circuits that receive power from a common d.c. bus. The d.c. bus connects to the a.c. power lines through a disconnect switch and a rectifier circuit and a chopper circuit is employed to dissipate power when the d.c. bus voltage rises due to motor regeneration. A power monitor and control circuit monitors the a.c. line voltage and the d.c. bus voltage and it controls the various system elements in such a manner as to maintain the d.c. bus voltage within an operating range. When the d.c. bus voltage cannot be maintained within the operating range, the disconnect switch is enabled to shut down the machine.
104 Citations
6 Claims
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1. In a drive system for a mining machine having a hoist motor, a crowd motor and a swing motor, the combination comprising:
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a rectifier circuit having inputs connected through lines to a source of a.c. power and an output terminal at which d.c. power is produced; disconnect means connected to said lines and being operable in response to a disable signal applied to a power enable input to disconnect said rectifier circuit from said a.c. power source; a d.c. bus connected to said rectifier output terminal; a set of inverters, each having an input connected to said d.c. bus, each having an output connected to one of said motors and each being operable in response to signals from an associated inverter control circuit to deliver power to its attached motor from said d.c. bus and to regenerate power to said d.c. bus from its attached motor; and a power monitor and control circuit which includes; a. voltage sensing means coupled to said a.c. power source for generating an analog signal which is proportional to the voltage applied to the inputs of said rectifier circuit; b. comparator means connected to said voltage sensing means for generating a preselected logic signal when said analog signal drops below a predetermined level; c. timer means connected to said comparator means and being enabled by said preselected logic signal to generate said disable signal to said disconnect means power enable input when said preselected logic signal is present for a preselected time interval; and d. means connected to said d.c. bus for generating a reduction signal to each of said inverter control circuits which reduces the power delivered by said inverters to their attached motors when the voltage of said d.c. bus drops below a preselected level. - View Dependent Claims (2, 3, 4, 5)
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6. In a drive system for a mining machine having a set of motors which each connect to provide separate machine motions, the combination comprising:
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a set of inverters, each inverter associated with one of said motors and each connected to deliver energy to its associated motor or to receive energy regenerated by its associated motor; a d.c. bus connected to each of said inverters to deliver energy to them and to receive energy from them which is regenerated by their associated motors; a rectifier circuit having an input connected to an a.c. power line and an output connected to said d.c. bus, said rectifier circuit being operable to deliver energy to said d.c. bus from said a.c. power line; and power monitor and control circuit means coupled to said d.c. bus and each of said inverters, said power monitor and control means being responsive to a drop in the energy delivered to the d.c. bus by said rectifier circuit to reduce the energy demanded by said inverters from said d.c. bus and to enable energy regenerated by any of said motors to be applied through its associated inverter to said d.c. bus, whereby energy generated by one or more machine motions is employed to maintain other machine motions which demand energy.
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Specification