Electricity: motive power systems – Induction motor systems
Patent
1992-07-20
1994-05-17
Shoop, Jr., William M.
Electricity: motive power systems
Induction motor systems
318685, 318437, 318 71, H02P 124
Patent
active
053131495
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a current supply control apparatus for an inductance load such as a magnetic bearing, a reluctance type motor, a stepping motor etc., more particularly to a current supply control apparatus capable of actuating a large inductance load without using a high voltage electrical power source, thereby improving a responsibility in a current supply control for an inductance load.
BACKGROUND ART
Conventionally, in the case where a large inductance load has to be actuated, a current supply control circuit is interposed between the inductance load and a high-voltage electrical power source so that an application of high voltage can be controlled by the current supply control circuit. For example, in order to realize a magnetic levitation of a rotor member in a magnetic bearing (i.e. a linear motor) using an electromagnet associated with a large inductance exciting coil, a high voltage is applied to the exciting coil so as to steeply build up an exciting current.
Furthermore, in a reluctance type motor with an exciting coil having a fairly large inductance for its armature, a voltage 5.about.10 times as large as a normal voltage for obtaining a normal motor output torque is applied to a current supply circuit during a building-up period of an exciting current in order to promptly build up the exciting current for preventing the motor output torque from being undesirably reduced. Also, a magnetic energy stored in the exciting coil is returned to an electric power source during a trailing-edge period of the exciting current, thereby quickly decreasing the exciting current to prevent a counter torque from being generated.
However, a voltage required for realizing a magnetic levitation of a rotor member in a magnetic bearing or a voltage applied to an exciting coil of a reluctance motor for building up an exciting coil are so large that a voltage of the electric power source becomes excessively large.
Furthermore, if an applied voltage to a reluctance motor is not sufficient, a building-up and a trailing-edge of an exciting current become so dull that not only a torque reduction appears in its building-up period but a counter-torque occurs in its trailing-edge period. This means that the motor cannot be driven at a high speed.
For example, in the case where a conventional reluctance type motor is driven by a battery as a driving source of an automotive vehicle, the rotational speed of the motor cannot be increased more than several hundreds rpm. Thus, the motor will not have any practical use. A stepping motor also has similar problems.
SUMMARY OF INVENTION
The purpose of the present invention is to provide a current supply control apparatus capable of actuating a large inductance load without using a high-voltage electric power source and also capable of improving a responsibility in a current supply control for an inductance load.
In order accomplish above purposes, the present invention provides a current supply control apparatus for an inductance load comprising: a first and a second switching elements interposed between a DC electric power source and said inductance load; a first and a second diodes inversely connected to respective connecting units each consisting of corresponding one of said first and second switching elements and an inductance load; a current detecting circuit for generating a detecting voltage representing a current flowing in said inductance load; a back-flow preventing diode connected in a forward direction with respect to the DC electric power source on the DC electric power source side; a capacitor connected to said back-flow preventing diode; and a chopper circuit for comparing said detecting voltage of the current detecting circuit with a standard voltage being variably set in a voltage waveform so as to turn on or off said first and second switching elements depending on the result of comparison.
Whereby, when the detecting voltage exceeds the standard voltage, the first and second switching elements are turned off; during this turni
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Kabushikigaisha Sekogiken
Masih Karen
Shoop Jr. William M.
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