EP0010979A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
AC electric motor driving circuit having overload protection circuitry
Assignee: Fanuc Corp
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Filing: 1979-11-02
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Granted: —
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Expires: 1999-11-02
Abstract
Abstract Overcurrent protection circuitry for an electric motor driving circuit (3) has an overcurrent detector (r,, r 2 , r 3 , 10) monitoring current (for example i 1 ) flowing to the motor (4). The circuitry is such that when an overcurrent is detected current delivery from the driving circuit (3) is interrupted (for example through the operation of comparator 10a, resetting flip-flops 93a, 93b, and through AND gates 94a, 94bto turn off current delivery transistors Q, and Q 2 ). The circuitry then operates so that current delivery is restored after the interruption (for example by pulses from pulse generator 96 acting to set flip-flops 93a and 93b). Upon such a restoration if detector (10) still detects an overcurrent current delivery is again interrupted (by resetting flip-flops 93a, 93b). The result is that the drive circuit (3) is allowed to supply current intermittently but not above a value preset in the overcurrent detector even when the motor is overloaded, thereby allowing the motor to run continuously without observable halt in operation.
Inventors
- 👤 Shigeki Kawada
- 👤 Hiroshi Ishida
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 03:55
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/53; H02M7/537; H02M7/5387; H02M7/53871; H02M7/53875; H02H; H02H7/00; H02H7/08; H02H7/0833; H02H9/00; H02H9/02
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
93 words
Overcurrent protection circuitry for an electric motor driving circuit, comprising: an overcurrent detector for monitoring current delivered from an output of the driving circuit to the motor; means for interrupting current delivery operation of the driving circuit in response to a signal from the overcurrent detector when the detector detects an overcurrent; and means operable to cause restoration of current delivery operation of the driving circuit after such an intermption; arranged so that when such a restoration occurs if an overcurrent is again detected current delivery is interrupted again and is subsequently restored.
Claim 2
Dependent Claim
93 words
Overcurrent protection circuitry for an electric motor driving circuit, comprising: an overcurrent detector for monitoring current delivered from an output of the driving circuit to the motor; means for interrupting current delivery operation of the driving circuit in response to a signal from the overcurrent detector when the detector detects an overcurrent; and means operable to cause restoration of current delivery operation of the driving circuit after such an intermption; arranged so that when such a restoration occurs if an overcurrent is again detected current delivery is interrupted again and is subsequently restored.
Claim 3
Dependent Claim
38 words
Overcurrent protection circuitry as claimed in claim 1, for a driving circuit having an inverter circuit for driving an A.C. motor, wherein the overcurrent detector is for monitoring A.C. current delivered from an output of the inverter circuit.
Claim 4
Dependent Claim
17 words
Overcurrent protection circuitry as claimed in claim 3, for an inverter circuit of the kind employing transistors.
Claim 5
Dependent Claim
174 words
Overcurrent protection circuitry as claimed in claim 1, 2 or 3, for a speed control system which includes an inverter circuit for converting a direct current into a polyphase alternating current in the form of a rectangular wave by the switching action of transistors, and an inverter control circuit for regulating the output frequency of the inverter circuit to a prescribed value, an A.C. motor being made to rotate by the alternating current supplied thereto by the inverter circuit, wherein the overcurrent detector is for monitoring current that flows through the output side of the inverter circuit, the means for interrupting current delivery operation interrupt the operation of the inverter control circuit, and the means operable to cause restoration of current delivery operation restore operation of the inverter control circuit for fixed periods, the operation of the inverter circuit being interrupted when the current flowing through the transistors thereof is caused by an overload in the A.C. motor to attain a predetermined value, and restored after the lapse of a fixed period of time.
Claim 6
Dependent Claim
48 words
Overcurrent protection circuitry as claimed in any preceding claim, wherein the overcurrent detector includes: an overcurrent value setting device, and a comparator for making a comparison between an output voltage produced by said overcurrent value setting device and a voltage proportional to the current monitored by the detector.
Claim 7
Dependent Claim
39 words
Overcurrent protection circuitry as claimed in claim 4, or as claimed in claim 5 when read as appended to claim 4, wherein the overcurrent detector monitors each output phase of the polyphase alternating current provided by the inverter circuit.
Claim 8
Dependent Claim
23 words
Overcurrent protection circuitry as claimed in claim 5, wherein the voltage developed by the overcurrent value setting device is capable of being varied.
Claim 9
Dependent Claim
66 words
Overcurrent protection circuitry as claimed in claim 4, wherein the means operable to cause restoration of current delivery operation comprise a flip-flop circuit and a pulse generator arranged so that the inverter control circuit,when in the interrupted state, is restored to the operative state by an output signal from said flip-flop circuit when the flip-flop circuit is set by a pulse generated by said pulse generator.
Claim 10
Dependent Claim
30 words
Overcurrent protection circuitry as claimed in claim 8, wherein the oscillation frequency of the pulse generator is higher than that of the power source employed for driving the A.C. motor.
Claim 11
Dependent Claim
20 words
Overcurrent protection circuitry as claimed in any preceding claim, in operative combination with the drive circuit and the electric motor.
References Cited (Backward Citations)
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