Electric motor control system for a beam-type pumping load

Claim 2

In combination with a beam-type pumping unit having an electric motor for driving said unit, and a first control circuit for shutting down said motor under pump-off conditions, said first control circuit comprising a power-supply circuit for connecting a source of electric energy to said motor, and a switch connected in said power-supply circuit for disconnecting said motor from said source of electric energy, the combination comprising a. a relay for controlling actuation of said switch, b. an impedance in said power-supply circuit for carrying motor-load current therethrough, c. means for developing a signal proportional to said motorload current, d1 . electronic means for passing said motor-load signal when in one state, and blocking same when in another state, d2 . switch means actuated by said beam for setting the state of said electronic means, e1. a difference amplifier having two input circuits, e2. one of said input circuits being connected to said electronic means (d1. ) and the other being connected to an adjustable normal load signal (e3), e4. second electronic means connected to the output of said difference amplifier (e1) for controlling an electric timing circuit (e5), and e6. third electronic means connected to said timing circuit (e5) for de-energizing said relay (a) whenever said motor-laod signal (c) is not greater than said normal load signal (e3).

Claim 3

The invention according to claim 1, wherein said first electronic means (d1) comprises d1a, a field-effect transistor, d1b. a capacitor, and d1c. circuit means for connecting said capacitor to said field-effect transistor (d1a ), and wherein said switch means (d2) comprises d2a. a pair of mercury switches mounted on said beam, and d2b. circuit means for connecting said switches (d2a ) to said capacitor (d1b ) for charging and discharging same at the beginning of the upstrokes and the downstrokes of said pumping unit, and wherein said second electronic means (e4) comprises e4a. a transistor, e4b. a second capacitor, e4c. circuit means for connecting said transistor (e4a ) to said second capacitor (e4b ) to discharge same and to start a time period of said timing circuit (e5), and wherein said third electronic means (e6) comprises e6a a unijunction transistor, e6b a second transistor, eec circuit means for connecting said unijunction transistor (e6a ) to said second capacitor (e4b ) and to said second transistor (e6b ) to trip said unijunction transistor (e6a ) when the charge has reached a predetermined amplitude and to cause said second transistor (e6b ) to conduct when said unijunction transistor (e6a ) has been tripped, and e6d additional circuit means for connecting said second transistor (e6b ) across the winding of said relay (a) for de-energizing same by short-circuiting when said second transistor (e6b) conducts.

Claim 4

In combination with a beam-type pumping unit having an electric motor for driving said unit, and a first control circuit for shutting down said motor under pump-off conditions, said first control circuit comprising a power-supply circuit for connecting a source of electric energy to said motor, and a switch connected in said power-supply circuit for disconnecting said motor from said source of electric energy, the combination comprising a. a relay for controlling actuation of said switch, b. an impedance in said power-supply circuit for carrying motor-load current therethrough, c. means for developing a signal proportional to said motor-load current, d3. electric switch means for passing said motor-load signal when in one state, and blocking same when in another state, d4. mechanical support means actuated by said beam for actuating said switch means (d3) from one said state to the other for electrically closing said switch only during downstrokes, e7. a difference amplifer having two input circuits. e8.one of said input circuits being connected to said electric switch means (d3), and the other being connected to an adjustable normal-load signal (e9), e10. electronic means connected to the output of said difference amplifer (e7) for controlling an electrical timing circuit (e11), and e12. second electronic means connected to said timing circuit (e11) for de-energizing said relay (a) whenever said motor-load signal (c) is not greater than said normal-load signal (e9).

Claim 5

In combination with a beam-type pumping unit having an electric motor for driving said unit, and a first control circuit for shutting down said motor under pump-off conditions, said first control circuit comprising a power-supply circuit for connecting a source of electric energy to said motor, and a switch connected in said power-supply circuit for disconnecting said motor from said source of electric energy, the combination comprising a. a relay for controlling actuation of said switch, b. an impedance in said power-supply circuit for carrying motor-load current therethrough, c. means for developing a signal proportional to said motor-load current, d3. electric switch means for passing said motor-load signal when in one state, and blocking same when in another state, d4. mechanical support means actuated by said beam for actuating said switch means (d3) from one said state to the other for electrically closing said switch only during downstrokes, e7. a difference amplifer having two input circuits. e8.one of said input circuits being connected to said electric switch means (d3), and the other being connected to an adjustable normal-load signal (e9), e10. electronic means connected to the output of said difference amplifer (e7) for controlling an electrical timing circuit (e11), and e12. second electronic means connected to said timing circuit (e11) for de-energizing said relay (a) whenever said motor-load signal (c) is not greater than said normal-load signal (e9).