Electrical short-cicruit monitoring arrangement for variable-speed, three-phase motors, including their feed lines
First Claim
1. An electric short-circuit monitoring circuit for a variable speed three-phase motor and the supply lines thereto, said circuit being of the type having a constant-current, d.c.-link converter with a line-commuted system-end thyristor converter, an intermediate reactance circuit, and a self-commuting machine-end converter, said monitoring circuit comprising:
- means for monitoring the magnitude level of a ripple voltage superimposed on an output of said d.c.-link converter as a consequence of motor voltage commutation and supplied to each of the three motor phases connected to the output;
means for filtering the ripple voltages to obtain harmonic frequency voltages thereof;
means for comparing the harmonic frequency ripple voltage magnitude level for each of the phases to a preset reference voltage amplitude;
means for generating an interrupt signal in the event that the magnitude of any one of the harmonic frequency ripple voltage levels falls below the preset voltage amplitude reference andmeans for interrupting the power supply to the motor in response to the interrupt signal.
1 Assignment
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Accused Products
Abstract
An electrical short-circuit monitoring arrangement for a three-phase motor, including its supply lines, whose speed is controlled by a constant-current d.c.-link converter. The harmonic ripple voltage superimposed on the motor voltage generated as a consequence of the commutation by the constant-current d.c.-link converter at the output of the converter is determined, filtered, and supplied to a phase-monitoring unit, which when dropping below a selected amplitude variable of the harmonic voltage of at least one phase, triggers the switching module whose switching mechanism activates a disconnect switch to interrupt the motor circuit upon occurrence of a switchoff signal.
18 Citations
7 Claims
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1. An electric short-circuit monitoring circuit for a variable speed three-phase motor and the supply lines thereto, said circuit being of the type having a constant-current, d.c.-link converter with a line-commuted system-end thyristor converter, an intermediate reactance circuit, and a self-commuting machine-end converter, said monitoring circuit comprising:
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means for monitoring the magnitude level of a ripple voltage superimposed on an output of said d.c.-link converter as a consequence of motor voltage commutation and supplied to each of the three motor phases connected to the output; means for filtering the ripple voltages to obtain harmonic frequency voltages thereof; means for comparing the harmonic frequency ripple voltage magnitude level for each of the phases to a preset reference voltage amplitude; means for generating an interrupt signal in the event that the magnitude of any one of the harmonic frequency ripple voltage levels falls below the preset voltage amplitude reference and means for interrupting the power supply to the motor in response to the interrupt signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification