Fault protection apparatus for traction motor circuit

• US 4,680,512 A
• Filed: 05/19/1986
• Issued: 07/14/1987
• Est. Priority Date: 05/19/1986
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Melocik, Grant C.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ro, Bentsu
• Application Number:
  US06/864,237
• Time in Patent Office: 421 Days
• Field of Search: 361/23, 361/30, 361/28, 361/29, 318/139, 318/345 C, 318/345 D, 318/345 H, 318/434, 318/445, 318/447, 318/484, 318/599
• US Class Current: 318/139
• CPC Class Codes: H02H 7/0844 Fail safe control, e.g. by comparing control signal and controlled current, isolating motor on commutation error

Abstract

Motor control circuits having fault protection devices are in commercial use today. Such devices typically include logic elements requiring a conditioned power supply, and are incapable of operation directly from the main motor power supply. The subject apparatus includes a timing circuit for monitoring the electrical conduction of a power switching element associated with an electrical motor. The apparatus produces a fault signal in response to the power switching element continuing to conduct for longer than a predetermined continuous period of time. A latch receives the fault signal and responsively produces a blocking signal. An interrupt circuit receives the blocking signal and responsively controllably blocks power from the motor power supply to the electrical motor. Each of the timing, latch, and interrupt circuits is adapted to operate directly from the motor power supply and independent of any intermediate logic power supplies or associated logic devices.

Claims

1. Apparatus for controllably disabling a electrical motor circuit in response to detecting a predetermined condition of a pulse modulated power switching element, said electrical motor circuit including an electrical motor serially connected to a power supply through said power switching element, comprising:

logic means for controllably operating said electrical motor in response to predetermined command signals;

a logic power supply connected between said motor power supply and said logic means and adapted to deliver conditioned electrical power to said logic means;

timing means for monitoring the electrical conduction of said ower switching element and producing a fault signal in resonse to said power switching element continuing to conduct for longer than a predetermined continuous period of time;

latch means for receiving said fault signal and responsively producing a blocking signal;

interrupt means for receiving said blocking signal and responsively controllably blocking power from said motor power supply to said electrical motor, said interrupt means including a line switch having switchable power terminals serially connected between said motor power supply and said electrical motor; and

wherein each of said timing, latch, and interrupt means is adapted to operate directly from said motor power supply independent of said logic power supply and said logic means.

2. Apparatus for controllably disabling an electrical motor circuit in response to detecting a predetermined condition of a pulse modulated power switching element, said electrical motor circuit including an electrical motor serially connected to a motor power supply through said power switching element, comprising:

logic means for controllably operating said electrical motor at a speed and direction responsive to predetermined command signals;

a logic power supply connected between said motor power supply and said logic means and adapted to deliver conditioned constant voltage electrical power to said logic means;

a timing circuit having a R/C timing element and being connected to said power switching element;

a semiconductor switch having a first input terminal connected to said timing circuit and a second input terminal connected to said motor power supply;

a line switch having a control element connected to said semiconductor switch and having switchable power terminals serially connected between said motor power supply and said electrical motor; and

each of said timing circuit and said semiconductor switch being free from connection to said logic power supply.