Electricity: electrical systems and devices – Safety and protection of systems and devices – Motor protective condition responsive circuits
Reexamination Certificate
2000-08-08
2001-06-26
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Motor protective condition responsive circuits
C361S093100, C361S115000, C361S062000
Reexamination Certificate
active
06252751
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to distributing alternating current to a plurality of motors and, in particular, to rectifying alternating current to direct current for distribution and fault isolation, and then inverting the direct current to alternating current to drive a plurality of motors.
BACKGROUND OF THE INVENTION
Motor drives are used in a wide variety of applications. Typically, industrial motor drives are designed to accept 60 Hz alternating current (AC) power distribution. Accordingly, each motor drive is connected to a 60 Hz AC bus by input power protection circuitry. The AC power is then rectified and inverted by more circuitry included in each motor drive. Further, power factor correction circuitry is required in each motor drive to maintain a unity power factor.
Prior art solutions have certain drawbacks. Including rectification circuitry, input power protection circuitry, and power factor correction circuitry in each motor drive (including a bulky filters and precharge circuitry), increases size, cost, complexity, and electromagnetic interference. Prior art systems attempt to reduce the electromagnetic interference using filters, but this further increases the system cost.
SUMMARY OF THE INVENTION
Accordingly, a system which reduces duplication of rectification circuitry, input power protection circuitry, and power factor correction circuitry is provided. Systems employing the techniques of the present invention can enjoy reduced electromagnetic interference, reduced conduction losses, reduced size, and lower cost.
In one aspect of the present invention,- an apparatus for distributing a first alternating electrical current to first and second alternating current motors is provided. The apparatus comprises an active rectifier for converting the first alternating electrical current to a direct electrical current. The apparatus further comprises a first motor drive for converting the direct electrical current to a second alternating electrical current to supply the first alternating current motor and a second motor drive for converting the direct electrical current to a third alternating electrical current to supply the second alternating current motor. Still further, the apparatus comprises an electrical bus coupled to the active rectifier, the first motor drive, and the second motor drive for distributing the direct electrical current from the active rectifier to the first and second motor drives.
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Hamilton Sundstrand Corporation
Jackson Stephen W.
Marshall O'Toole Gerstein Murray & Borun
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