Current limit control circuit

• US 4,514,665 A
• Filed: 01/05/1983
• Issued: 04/30/1985
• Est. Priority Date: 01/05/1983
• Status: Expired due to Term

• Current Assignee: Towmotor Corporation (Caterpillar Incorporated)
• Original Assignee: Towmotor Corporation (Caterpillar Incorporated)
• Inventors: Pickering, William, Melocik, Grant C.
• Primary Examiner(s): Weldon, Ulysses
• Application Number:
  US06/455,720
• Time in Patent Office: 846 Days
• Field of Search: 361/23-25, 361/27, 361/30, 361/31, 361/33, 361/88, 361/90, 361/91, 361/93, 361/100, 361/101, 361/103, 318/138, 318/139, 318/345 E
• US Class Current: 318/139
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 3/04 Cutting off the power supply under fault conditions protective devices and circuit arrangements in general H01H; H02H
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• CPC Class Codes: H02P 5/68 controlling two or more dc dynamo-electric motors H02P5/46, H02P5/60 take precedence
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y10S 388/903 Protective, e.g. voltage or current limit
• CPC Class Codes: Y10S 388/934 Thermal condition

Abstract

Apparatus (10) is provided for controlling current through a motor (12), including a circuit (14) for generating motor speed command data, a circuit (26) for generating a control signal in response to a maximum value of current through the motor (12), a programmable data processor (72) for generating pulse trains in response to the command data, and a controllable supplying circuit (18) for coupling and decoupling power to the motor (12) in response to the pulse trains and for decoupling power to the motor (12) in response to the control signal independent of the pulse trains. By decoupling power from the motor (12) independent of the control produced by the data processor (72), the current limit is achieved even if the data processor (72) malfunctions, contrary to prior apparatus.

Claims

1. Apparatus (10) for controllably energizing a motor (12), comprising:

a DC electric power source (32) controllably connected to said motor (12);

generating means (14) for producing a predetermined plurality of incremental coded digital motor speed command signals;

first means (22) for receiving said digital motor speed command signals and producing respective predetermined pulse trains in response to each of said received command signals, each of said pulse trains having a predetermined duty factor;

controllable supplying means (18) for receiving said pulse trains and delivering electric current from said power source (32) to said motor (12), said controllable supplying means (18) including a power switching element (88) connected between said power source (32) and said motor (12), and a logic gate (84) having a first input connected to said first means (22), a second input connected to a second means (26), and an output connected to said power switching element (88);

a current shunt connected in series with said motor (12) and said power source (32), and adapted to produce a current signal in response to the magnitude of current delivered to said motor (12);

said second means (26) for receiving said current signal and producing a digital logic blocking signal in response to said current signal exceeding a predetermined magnitude, said second means (22) including a current reference potentiometer (102);

a differential amplifier (92) having a pair of inputs (84) connected across said shunt, and an output;

a first comparator (98) having a first input connected to said differential amplifier (92) output, a second input connected to said reference potentiometer (102), and an output;

a latch (103) having a first input connected to said comparator (98) output, a second input connected to said first means (22) and to said logic gate (84) first input, and an output;

a voltage divider (114); and

,

a second comparator (110) having a first input connected to said latch (103) output, a second input connected to said voltage divider (114), and an output connected to said logic gate (84) second input; and

,

wherein said controllable supplying means (18) is adapted to receive said digital blocking signal and block the delivery of current from said power source (32) to said motor (12) in response to said received blocking signal.