Tachometer check apparatus

• US 4,575,664 A
• Filed: 03/12/1984
• Issued: 03/11/1986
• Est. Priority Date: 03/12/1984
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Johnson, Frederick O.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Ip, Shik Luen Paul
• Application Number:
  US06/588,637
• Time in Patent Office: 729 Days
• Field of Search: 318/311, 318/312, 318/313, 318/314, 318/315, 318/316, 318/317, 318/318, 318/326, 318/327, 318/345 A, 318/490, 318/618, 318/628, 324/160-166
• US Class Current: 388/822
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: Y10S 388/909 Monitoring means
• CPC Class Codes: Y10S 388/91 Operational/differential amplifier
• CPC Class Codes: Y10S 388/916 Threshold circuit
• CPC Class Codes: Y10S 388/921 Timer or time delay means

Abstract

An electronic motor control system is taught herein which utilizes a tachometer check circuit. The tachometer check circuit is an electrical circuit which is interconnected with the output terminals of the tachometer. The circuit is utilized when the tachometer is at standstill to determine if the tachometer is functional, that is, is it internally correctly wired to produce an expected signal upon rotation. If such is the case, then motor start-up may take place. A second test is performed after motor start-up for determining if an appropriate amount of output voltage is being produced by the tachometer during the start-up phase. This is based on expected values of voltage during a short period of time after start-up. If such is not the case, the motor control system is disabled and the motor is stopped. The system is utilized for embodiments which include AC tachometers as well as DC tachometers used on unidirectional or bidirectional rotational systems.

Claims

1. A speed-controlled motor system, comprising:

(a) electric motor means with a rotating member for driving a load at a predetermined angular velocity;

(b) motor controller means interconnected with said electric motor means for causing said rotating member to rotate at said predetermined angular velocity when actuated;

(c) tachometer means with output voltage terminal means interconnected with said rotating member for generating a tachometer means output voltage at said output voltage terminal means which is indicative of the angular velocity of said rotating member, said tachometer means being interconnected at said output voltage terminal means with said motor controller means for providing said tachometer means output voltage thereto for being utilized by said motor controller means to maintain the angular velocity of said rotating member at said predetermined angular velocity within limits; and

(d) combination motor control starter and tachometer checker means interconnected with said tachometer means output voltage terminal means and said motor controller means for simultaneously actuating said motor controller means to cause said rotating member to rotate and initiate a tachometer means check to stop said rotating member from continued rotation if a minimum output check voltage value is not present at said output voltage terminal means at a predetermined time after said motor controller means has been actuated, comprising;

(i) a power supply means;

(ii) voltage time delay means for providing an output feedback signal at the end of said predetermined time unless sooner disabled at a disable terminal thereof;

(iii) disable comparator means interconnected at the input thereof with said tachometer means output voltage terminal means and connected at the output thereof within said voltage time delay means for providing a disabling condition for said voltage time delay means when the voltage on said output voltage terminal means exceeds said minimum output check voltage; and

(iv) switch means connected at one pole thereof between said power supply means and said voltage time delay means and connected at another pole thereof with said motor controller means for simultaneous actuation of said motor controller means and connection of said power supply means to said voltage time delay means so that said output feedback signal will be provided after said predetermined time unless sooner disabled, said disabling occurring if said minimum output check voltage is reached before the end of said predetermined time.