Method to control stops of an intermittently operating driving motor

Claim 1

A method to control stopping of an electric motor for a pump, the stopping being dependent upon the current consumption of the motor, comprising the steps of: coupling a current signal from one phase of said motor to a transformer, and connecting said current signal from the output of the transformer to a rectifier; rectifying said current signal and coupling said rectified signal to a derivative sensing circuit and an RMS converting filter circuit; generating a derivative signal representing an actual current consumption value in said derivating sensing circuit and coupling said derivative signal to a microprocessor; producing a mean current value in said RMS circuit and coupling said mean current value to said microprocessor, said microprocessor having previous predetermined stored mean values; comparing in said microprocessor the actual current consumption value with a stored mean value of the nearest previous predetermined stored mean values; and stopping the motor when a predetermined difference is detected between the actual current consumption value and the stored mean value of the nearest previous predetermined stored mean values.

Claim 2

A method to control stopping of an electric motor for a pump, the stopping being dependent upon the current consumption of the motor, comprising the steps of: coupling a current signal from one phase of said motor to a transformer, and connecting said current signal from the output of the transformer to a rectifier; rectifying said current signal and coupling said rectified signal to a derivative sensing circuit and an RMS converting filter circuit; generating a derivative signal representing an actual current consumption value in said derivating sensing circuit and coupling said derivative signal to a microprocessor; producing a mean current value in said RMS circuit and coupling said mean current value to said microprocessor, said microprocessor having previous predetermined stored mean values; comparing in said microprocessor the actual current consumption value with a stored mean value of the nearest previous predetermined stored mean values; and stopping the motor when a predetermined difference is detected between the actual current consumption value and the stored mean value of the nearest previous predetermined stored mean values.

Claim 3

A method to control stopping of an intermittently operating electric motor for a pump by detecting the current consumption in one phase of the winding of the electrical motor, comprising the steps of: coupling a current signal from said one phase to a transformer; receiving said current signal from the transformer in a rectifying circuit, and rectifying said current signal; simultaneously coupling said rectified current signal to a derivative sensing circuit and an RMS converting filter circuit; generating in said derivative sensing circuit a derivative sensing signal having a large negative derivative value when the pump begins to pull in air, and coupling said derivative sensing signal to a microprocessor; producing a mean current value in said RMS circuit and coupling said mean current value to an A/D converter in said microprocessor; comparing in said microprocessor said derivative sensing signal representing the actual current value with said mean current value from said converter; and initiating a stopping signal in said microprocessor to stop the motor when a predetermined difference between said actual current value and said mean current value is detected by said microprocessor.

Claim 4

A method to control stopping of an intermittently operating electric motor for a pump by detecting the current consumption in one phase of the winding of the electrical motor, comprising the steps of: coupling a current signal from said one phase to a transformer; receiving said current signal from the transformer in a rectifying circuit, and rectifying said current signal; simultaneously coupling said rectified current signal to a derivative sensing circuit and an RMS converting filter circuit; generating in said derivative sensing circuit a derivative sensing signal having a large negative derivative value when the pump begins to pull in air, and coupling said derivative sensing signal to a microprocessor; producing a mean current value in said RMS circuit and coupling said mean current value to an A/D converter in said microprocessor; comparing in said microprocessor said derivative sensing signal representing the actual current value with said mean current value from said converter; and initiating a stopping signal in said microprocessor to stop the motor when a predetermined difference between said actual current value and said mean current value is detected by said microprocessor.