Electricity: motive power systems – Braking – Dynamic braking
Patent
1997-09-11
2000-06-20
Salata, Jonathan
Electricity: motive power systems
Braking
Dynamic braking
318375, H02P 300
Patent
active
060781572
DESCRIPTION:
BRIEF SUMMARY
RELATED ART
The invention is based on a circuit for operating an electric motor of the generic type having a semiconductor component contained in a circuit in parallel with the motor.
U.S. Pat. No. 3,487,282 discloses a generic circuit having a thyristor that is contained in a circuit in parallel to a motor. The thyristor is provided for short-circuiting the motor to permit fast braking. A switching transistor that connects a connection of the electric motor to a voltage source as a function of a control signal is provided for switching the electric motor on and off. The inductive voltage peak appearing at the electric motor during the connected-off process is eliminated by a diode switched in parallel to the electric motor.
The abstract of JP 1043082 discloses a further circuit that has a bidirectional thyristor (triac) switched in parallel to the motor. This thyristor is switched on due to a stop signal, causes a short-circuit current and brakes the motor by means of a short-circuit brake.
It is the object of the invention to provide a circuit for operating an electric motor which, with simple means, permits the damping of inductive voltage peaks and braking of the electric motor.
SUMMARY AND ADVANTAGES OF THE INVENTION
The above object generally is achieved according to the present invention by a circuit for operating an electric motor having a triac that is contained in a circuit in parallel to the electric motor, and a control signal that is produced by a signal generator for the triac, with the control signal enabling the current path in one direction in the triac. A further control signal that is dependent on the voltage appearing at a connection of the electric motor is provided for the triac and enables the current path in the opposite direction in the triac.
The circuit of the invention can be embodied particularly inexpensively. In accordance with the invention, a bidirectional thyristor (triac) is provided that is connected in parallel to the electric motor. The triac includes two thyristors that operate in anti-parallel and are integrated into a single silicon crystal. The component includes only one control electrode, by way of which the current path can be enabled (triggered) in the two directions by a pulse, depending on the polarity of the external voltage. The bidirectional thyristor is referred to hereinafter as a triac. The triac takes over both the damping of the inductive voltage peak during the switch-off process of the electric motor and the short-circuiting of the electric motor during the braking process. To embody the circuit of the invention, only a single semiconductor component is required that is also available in a configuration of a surface-mounted device (SMD). The SMD embodiment requires little space on a printed circuit board, and can be attached automatically, resulting in cost advantages in mass production.
The triac provided in accordance with the invention is acted upon by a first control signal that is dependent on the voltage appearing at the electric motor. The first control signal is therefore suited for damping the inductive voltage peak during the switch-off process of the electric motor. The triac is acted upon by a second control signal produced by a signal generator. The second control signal is suited for braking the electric motor.
The basic features of the invention particularly permit reliable operation of the electric motor in applications providing a separation of the circuit from a voltage source by means of a switch. In particular, the first control signal, being a function of the voltage appearing at the electric motor, ensures, in connection with the triac, the damping of the inductive voltage peak during the switch-off process of the electric motor, even after the switch has been opened.
A measure that can be implemented particularly simply provides that the first control signal, being dependent on the voltage appearing at the electric motor, is obtained from the motor voltage by means of a diode. The diode connected directly to a connection o
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patent: 3487282 (1969-12-01), Gasiorek et al.
patent: 4104571 (1978-08-01), Gurwicz et al.
patent: 4271383 (1981-06-01), Endo
patent: 4275341 (1981-06-01), Huber et al.
patent: 4423363 (1983-12-01), Clark et al.
patent: 5463540 (1995-10-01), Jones
patent: 5705903 (1998-01-01), Hastings
Grass Ansgar
Seiler Hartmut
Kunitz Norman N.
Robert Bosch GbmH
Salata Jonathan
Spencer George H.
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