Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2000-03-31
2001-03-27
Nguyen, Matthew (Department: 2837)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S050000
Reexamination Certificate
active
06208536
ABSTRACT:
BACKGROUND INFORMATION
A drive device with a safety device for special operation is described in German Patents No. 43 30 823. In this patent a redundant safety device is provided to monitor the motor, verifying that the motor speed does not exceed a predetermined maximum value in special operation and to interrupt the power supply to the motor when the rotational speed is greater than the predetermined maximum value. To determine the rotational speed, two different signals are detected so that the first signal is obtained from a rotational speed sensor and the second signal is derived in at least one phase feeder to the motor from the variation of current over time detected for this purpose by a second sensor. If the detected rotational speed exceeds a predetermined maximum value, the energy supply to the motor is interrupted by switching a circuit breaker upstream from a power rectifier and in addition switching off the power inverter.
Additional monitoring of the actuation signals for the interruption of the power supply is however not provided. A break in a feeder or a short-circuit is not monitored separately.
SUMMARY OF THE INVENTION
The safety device for a drive according to the present invention is provided with a monitoring system, which evaluates a measured value describing the operating state of the drive in order to ascertain whether an operation in emergency mode should be started to replace operation in normal mode. The monitoring system generates at least one first output signal for an actuating element that influences the power supply to the motor. In the safety device according to the present invention for a drive, an a.c. signal is used in normal operation as the output signal and a d.c. signal is used in emergency operation. Thanks to the pre-definition of the form of the output signal, the d.c. signal transmitted on purpose for emergency operation also applies to the operating state which occurs in case of short-circuit or rupture of the feeder which transmits the output signal. A signal monitoring system is thereby enabled to actuate the appropriate actuating elements for an emergency operation in case of an emergency operation initiated on purpose, as well as in a critical situation caused by a feeder rupture or a short-circuit. No separate system to monitor the operability of the feeder is needed.
In an advantageous further development, the actuating element is assigned a signal monitoring system, which monitors the output signal and actuates the actuating element for an emergency operation when the input signal, which matches the output signal when the feeder is working properly, is a d.c. signal. The signal monitoring system is preferably located in the immediate proximity of the actuating element in order to thus minimize signal transmission errors.
In an advantageous further development, the output signal is transmitted via a bus. The above described safety function can be integrated into the signal processing which is necessary for the exchange of bus signals. A suitable hardware or software design only insignificantly increases the electronics costs, which is necessary in any case to operate the bus system.
REFERENCES:
patent: 4642475 (1987-02-01), Fischer et al.
patent: 5255178 (1993-10-01), Liberati
patent: 680 067 (1992-06-01), None
patent: 43 30 823 (1995-03-01), None
patent: 196 53 421 (1998-06-01), None
patent: 2 281 826 (1995-03-01), None
Boesche Guenther
Kunz Olaf
Weber Rupert
Kenyon & Kenyon
Nguyen Matthew
Robert & Bosch GmbH
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