Electronic overload relay power source

A device for interrupting the current flow in an electrical power conductor comprising:

• a contactor including at least one pair of contacts connectable to the conductor to open the electrical path of the power conductor and a solenoid having a winding connectable to the power conductor, the solenoid being configured to maintain engagement of the contacts when the winding is energized;
• a switch coupled to the winding to interrupt current flow from the power conductor to the winding upon opening;
• an electronic control unit coupled to the switch and configured to determine when to open the switch;
• and
• a current transformer consisting essentially of a further winding that is magnetically coupled to a conductor which conductor is series connected to the winding of the solenoid the further winding providing electrical power to the control unit when the contacts of the contactor are engaged.

An overload relay operable to apply electric power to a motor from first, second and third power conductors coupled to a three-phase power supply, the relay comprising:

• a contactor including first, second and third pairs of contacts, one of each pair connectable to the first, second and third power conductors, respectively, the other of each pair connectable to an electric motor, the contactor including a solenoid having a winding and closing the pairs of contacts when the winding is energized;
• a switch coupled to the winding to interrupt current flow through the winding when opened, the winding being supplied current from at least one of the power conductors;
• an electronic control unit coupled to the switch and configured to determine when to open the switch;
• and
• a current transformer consisting essentially of a further winding which is magnetically coupled to at least one conductor which supplies current to the winding of the solenoid, the current transformer being connected in series with the solenoid winding, the further winding providing electrical power to the control unit when the contacts of the contactor are engaged.

A device for interrupting the current flow in an electrical power conductor comprising:

• a contactor including at least one pair of contacts connectable to the conductor to open the electrical path of the power conductor;
• a solenoid having a winding connectable to the power conductor, the solenoid being configured to maintain engagement of the contacts when the winding is energized;
• a switch coupled to the winding to interrupt current flow from the power conductor to the winding upon opening;
• a first current transformer magnetically coupled to the power conductor for monitoring the current flow in the power conductor;
• an electronic control unit coupled to the switch and configured to determine when to open the switch based on the current flow monitored by said first transformer;
• and
• a second current transformer consisting essentially of a further winding which is magnetically coupled to a conductor which is series connected between the power conductor and the winding of the solenoid the further winding providing electrical power to the control unit when the contacts of the contactor are engaged.