Electricity: motive power systems – Synchronous motor systems
Patent
1997-05-09
1999-05-18
Sircus, Brian
Electricity: motive power systems
Synchronous motor systems
318706, 318799, 340648, G08B21/00
Patent
active
059053542
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a sensor for verifying that a three phase AC motor has stopped rotating, and in particular to sensor technology for also verifying that rotation of the motor due to inertia has stopped after shutting off the motor power source.
BACKGROUND ART
As a sensor for verifying that a motor has stopped rotating, there is, for example one, which uses an electromagnetic pickup (refer to PCT Publication No. WO94/23303 (PCT/JP93/00411)).
With this device, a metal disc having a plurality of metallic protrusions located at even spacing around the surface periphery thereof is secured to a motor rotation shaft, and an electromagnetic pick up, serving as a sensor head, is provided at a location facing the protrusions at a predetermined distance therefrom. When the metal disc rotates with rotation of the motor, fluctuations are produced in a magnetic flux with the passing of the respective protrusion. By subjecting the resultant fluctuations in the output from the electromagnetic pick up, due to these magnetic flux fluctuations, to threshold value processing or the like, using a signal processing circuit, then during rotation of the motor (including rotation under inertia), an output of logic value 0 showing that the motor is rotating (danger side) is produced from the signal processing circuit, while when the motor rotation has practically stopped (safe side), an output of logic value 1 is produced from the signal processing circuit.
However, in devices which use an electromagnetic pickup for the sensor head, the spacing between the protrusions and the electromagnetic pick up is extremely small. Moreover, this spacing must be controlled very accurately. Therefore, the sensor head attachment operation becomes difficult. Furthermore, there is a problem in that the fitted location of the pickup head and related parts must be periodically checked, thus increasing maintenance and inspection costs.
Moreover, the circuit configuration for prohibiting generation of a motor stopped judgment output, for the period including from after shutting off the motor power source until motor rotation under inertia has reduced to a sufficiently slow speed is complicated.
The present invention takes into consideration the abovementioned situation, with the object of providing a motor stopped verification sensor which does not have an electromagnetic pickup type sensor head, thus obviating the need for control of the attachment position, and hence the attachment operation is extremely simple.
SUMMARY OF THE INVENTION
Accordingly, with the motor stopped verification sensor according to the present invention the construction comprises: a sensor section having three signal input lines for respectively connecting to three power supply lines of a three phase AC motor, the three signal input lines being connected such that a closed circuit is made up with one of the three power supply lines as a common power supply line, and the other two power supply lines connected together in parallel, and a high frequency signal of a lower level than the level of a motor drive power source is supplied to the closed circuit from the signal input line connected to the common power supply line, and a difference in the value of the currents respectively flowing in the other two signal input lines is sampled to determine whether to output a motor stopped signal or a motor rotating signal.
With such a construction, there is no sensor head as with the electromagnetic pickup type, thus obviating the need for control of the attachment position. Hence sensor attachment is extremely simple.
Moreover the construction includes provision of: a signal processing circuit for generating an output of logic value 1 corresponding to a high energy condition when a level of a signal sampled by the sensor section is within a predetermined range, and generating an output of logic value 0 corresponding to a low energy condition when outside the predetermined range; and a first on-delay circuit for delaying the output of logic value 1 f
REFERENCES:
patent: 3976919 (1976-08-01), Vandevier et al.
patent: 4520300 (1985-05-01), Fradella
patent: 4661880 (1987-04-01), Futsuhara
patent: 4757417 (1988-07-01), Futsuhara
patent: 5027114 (1991-06-01), Kawashima et al.
patent: 5337206 (1994-08-01), Kadah et al.
patent: 5561358 (1996-10-01), Kuwabara et al.
patent: 5568059 (1996-10-01), Futsuhara et al.
patent: 5568131 (1996-10-01), Sakai et al.
patent: 5677606 (1997-10-01), Otake
patent: 5706153 (1998-01-01), Innes et al.
Futsuhara Koichi
Shirai Toshihito
Tajima Junpei
Sircus Brian
The Nippon Signal Co. Ltd.
LandOfFree
Motor stopped verification sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor stopped verification sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor stopped verification sensor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1761901