Motor drive system and method

An electrical motor drive configured to start a progressive cavity pump in a normal mode of operation in a water pumping system, the electrical motor drive comprising a controller including control logic configured to perform a method comprising:

• performing repeated starting attempts to overcome stiction in the progressive cavity pump by attempting to supply power to an electrical motor driving the progressive cavity pump at increasing power levels in each starting attempt and supplying the power at the increasing power levels if the power is available from a power source;
• and
• after each starting attempt:
• reducing the power applied to the electrical motor to a reduced power level;
• determining a rotational speed of the electrical motor at the reduced power level;
• determining if the rotational speed matches a speed corresponding to the reduced power level applied to the electrical motor;
• if the rotational speed does not match the speed corresponding to the reduced power level, and a predetermined number of the starting attempts has not been reached, performing a next starting attempt;
• and
• if the rotational speed does match the speed corresponding to the reduced power level, entering the normal mode of operation.

A water pumping system comprising:

• a progressive cavity pump;
• an electrical motor coupled to the progressive cavity pump;
• and
• an electrical motor drive to power the electrical motor, the electrical motor drive configured to start the progressive cavity pump and to drive the progressive cavity pump in a normal mode of operation after starting the progressive cavity pump, the motor drive including a controller comprising control logic configured to perform a method comprising:
• performing repeated starting attempts to overcome stiction in a progressive cavity pump by attempting to supply power to an electrical motor driving the progressive cavity pump at increasing power levels in each starting attempt and supplying the power at the increasing power levels if the power is available from a power source;
• and
• after each starting attempt:
• reducing the power applied to the electrical motor to a reduced power level;
• determining a rotational speed of the electrical motor at the reduced power level;
• determining if the rotational speed matches a speed corresponding to the reduced power level applied to the electrical motor;
• if the rotational speed does not match the speed corresponding to the reduced power level, and a predetermined number of the starting attempts has not been reached, performing a next starting attempt;
• and
• if the rotational speed does match the speed corresponding to the reduced power level, entering the normal mode of operation.