PCB motor controller with POW switching

A system comprising:

• a printed circuit board having three phase conductors for conveying incoming three phase power from a source and for outputting three phase power to a three-phase AC electric motor;
• a power supply mounted on and electrically coupled to the printed circuit board;
• control circuitry mounted on and electrically coupled to the printed circuit board and receiving power from the power supply;
• at least one current sensor that, in operation, senses a current of the incoming power and to provide signals representative thereof to the control circuitry;
• three single pole relays mounted on and electrically coupled to respective phase conductors to receive the incoming power and to provide the outgoing power when closed, the relays each having a direct current operator that receives control signals from the control circuitry to switch in accordance with a point-on-wave switching scheme to close at desired times of an AC waveform of the incoming power and thereby complete current carrying paths from the source through the power conductors to the motor, and to open at desired times to interrupt power to the motor;
• wherein the system comprises only electromechanical switching devices;
• and
• wherein the control circuitry, in operation, utilizes a sensed current for only one phase of the incoming three phase power to open one of the single pole relays prior to opening the other two of the single pole relays in accordance with the point-on-wave switching scheme.

A motor starter comprising:

• a printed circuit board having three phase conductors for conveying incoming three phase power from a source and for outputting three phase power to a three-phase AC electric motor;
• control circuitry mounted on and electrically coupled to the printed circuit board and receiving power from a power supply;
• at least one current sensor that, in operation, senses a current of the incoming power and to provide signals representative thereof to the control circuitry;
• at least two voltage sensors that, in operation, sense voltage waveforms of the incoming power and provide signals representative thereof to the control circuitry;
• three single pole relays mounted on and electrically coupled to respective phase conductors to receive the incoming power and to provide the outgoing power when closed based upon signals from the control circuitry to start the electric motor;
• and
• wherein the control circuitry, in operation, utilizes a sensed current for only one phase of the incoming three phase power to open one of the single pole relays prior to opening the other two of the single pole relays in accordance with the point-on-wave switching scheme;
• and
• wherein the control circuitry, in operation, utilizes sensed voltage for only two phases of the incoming three phase power to close two of the single pole relays prior to closing the other single pole relay in accordance with the point-on-wave switching scheme.