Overvoltage suppression technique for variable frequency drives operating reciprocating loads
First Claim
1. A control method for overvoltage suppression of a variable frequency drive (VFD) operating a motor to drive a reciprocating load, comprising:
- controlling the VFD to operate the motor at a select reference frequency;
predicting occurrence of a negative motor torque condition; and
in response to a predicted negative torque condition controlling the VFD to operate the motor at a higher frequency than the select reference frequency.
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Accused Products
Abstract
A motor control for a reciprocating load includes overvoltage suppression. The motor control comprises a variable frequency drive (VFD) operatively connected to a power source for operating a motor to drive the reciprocating load. A sensor determines motor torque. A control unit is connected to the VFD and to the sensor and is adapted to control the VFD in a normal mode to operate the motor at a select reference frequency. The control unit predicts occurrence of a negative motor torque condition based on sensed motor torque and in response to a negative motor torque condition controls the VFD in a negative motor torque mode to operate the motor at a higher frequency than the select reference frequency to prevent the motor from entering a negative slip condition.
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Citations
18 Claims
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1. A control method for overvoltage suppression of a variable frequency drive (VFD) operating a motor to drive a reciprocating load, comprising:
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controlling the VFD to operate the motor at a select reference frequency;
predicting occurrence of a negative motor torque condition; and
in response to a predicted negative torque condition controlling the VFD to operate the motor at a higher frequency than the select reference frequency. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A control for overvoltage suppression of a variable frequency drive (VFD) operating a motor to drive a reciprocating load, comprising:
a control unit adapted to control the VFD in a normal mode to operate the motor at a select reference frequency, and to control the VFD in a negative motor torque mode to operate the motor at a higher frequency than the select reference frequency, whereby the control unit prevents the motor from entering a negative slip condition. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A motor control for a reciprocating load including overvoltage suppression, comprising:
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a variable frequency drive (VFD) operatively connected to a power source for operating a motor to drive the reciprocating load;
means for determining motor torque; and
a control unit connected to the VFD and to the determining means and adapted to control the VFD in a normal mode to operate the motor at a select reference frequency, and to predict occurrence of a negative motor torque condition based on sensed motor torque and in response to a negative motor torque condition controlling the VFD in a negative motor torque mode to operate the motor at a higher frequency than the select reference frequency to prevent the motor from entering a negative slip condition. - View Dependent Claims (14, 15, 16, 17, 18)
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Specification