METHOD FOR PROTECTING ELECTRIC DRIVE OF A PUMP AT FAILURE IN LIQUID SUPPLY AT ITS INLET

This invention relates to pump-building. A method for protecting the electric drive of a pump at failure in liquid supply at its inlet comprises measuring the electric parameters of the electric drive, forming the signal controlling the unit switch-off, with comparing the signal to prescribed value and switching off the unit. At that, as electric parameter active power is used. Control signal is formed as being proportional to the product of amplitude value of the voltage and instant value of current corresponding to the amplitude value of voltage at given instant. As prescribed value values of operational active power of the electric drive are used, those are set. Signal for the unit switch-off is formed with a delay, value of the delay is changed depending on the value of the time interval between the end and the repetitive beginning of failures of liquid supply at the inlet of the pump. At that, comparison of the time interval between the end and the repetitive start of failures in supply to prescribed value is performed. In the case of the interval being smaller than the prescribed one time delay for formation of the signal for the unit switch-off is decreased, for instance, by a multiple, and at its achieving zero value and coincidence with prescribed value of the delay of the signal for switching-off the unit formation at permanently present failure of supply signal is given for the unit switch-off at the control signal being smaller than the prescribed one. This invention provides exclusion of wrong signals for electric drive switch-off at failure in liquid supply at the inlet of the pump, and obtaining prescribed reliability and accuracy for different wells without additional adjustment. Изобретение относится к насосостроению. Способ защиты электропривода насоса при срыве подачи жидкости на его входе состоит в измерении электрических параметров электропривода, формировании сигнала, который управляет отключением агрегата, сравнении сигнала с заданной величиной и отключении агрегата. При этом как электрический параметр используют активную мощность. Управляющий сигнал формируют пропорционально произведению амплитудного значения напряжения и мгновенного значения тока, который соответствует амплитудному значению напряжения в данный момент времени. Как заданную величину используют значение активной рабочей мощности электропривода, которое задается. Сигнал на отключение агрегата подают с задержкой, значения которой изменяют в зависимости от значения интер