Kabushiki Kaisha Yaskawa Denki

Tetsuo Kawano

Koji Kawamoto

Richard L Pratt

Takayuki Yamakawa

Toshio Miyano

Yoichi Yamamoto

Hidetoshi Ryu

Brian Mackinnon

Tatsumi Tsuruta

Frederick C Lach

Noriyuki Takada

It is an object of the invention to provide a pump jack pump-off control method and a pump jack control apparatus in which, even when the speed of a pump jack is reduced due to generation of a pump-off condition, the pump jack is not caused to stop due to the motor overload abnormality or the coagulated crude oil and, even when the pump-off condition is generated, the reduction of the production capacity of the pump jack can be prevented as much as possible. On detecting the pump-off condition, while the pump jack is in operation with the speed thereof being reduced, or while the pump jack is in operation at the lowest speed, according to the overload warning signal of an ac electric motor, the pump jack is switched over to its intermittent operation. Also, the pump jack can be operated in such a manner that the stroke speed of the pump jack in the up stroke operation can be switched from a sinusoidal wave form over to a rectangular wave form, or, in the operation of the pump jack by an inverter, the pump jack can be operated such that it can carry out its up stroke operation with a limit imposed on torque.

Pump jack pump-off control method and pump jack control apparatus

A pump off control method comprises detecting the speed of the induction motor and an instantaneous value of secondary current of the induction motor. Down stroke time in every cycle of the pump jack is detected. An average value of instantaneous values of the secondary current of the induction motor in the down stroke time in said every cycle is calculated. An average value reference of the secondary current of the induction motor to be compared with calculated average value of the instantaneous values of the secondary current of the induction motor is set. The calculated average value of the instantaneous values of the secondary current is compared with the average value reference after the down stroke end in each cycle. An occurence of pump off is detected if the calculated average value of the instantaneous values is greater than the average value reference.

Pump-off control method of pump jack

Rope steadying control method and apparatus for crane or the like

Growing community of inventors

Fukuoka, Japan

Tetsuo Kawano