Power supply circuit of a high speed electric motor

A power control system for an electric motor having at least one magnetic bearing, said system comprising:

• a main power supply;
• a DC link bus connected to said main power supply, said bus supplying power for the electric motor and for a bearing actuator;
• a motor controller;
• a bearing controller;
• a supervisory controller;
• a DC/DC converter supplied from said DC link bus, said DC/DC converter providing low voltage DC power supply for said motor controller, said beanng controller and said supervisory controller,
• said supervisory controller receiving signals from an AC power monitor and a capacitor connected across said DC link bus, said supervisory controller then signaling said motor controller, said motor controller controlling IGBT switches connecting motor winding to the DC link bus in accordance with a position of a rotor of the motor;
• each switch having a parallel diode of a polarity opposing a motor current flow during normal operation of said main power supply;
• wherein, in one of:
• signals of failure from the AC power monitor and of:
• a drop in a voltage across said capacitor, all switches are turned off and an existing current in the motor winding flows through corresponding diodes to the DC link bus, thereby providing an immediate boost to a voltage of the DC link bus;
• when the DC link bus voltage drops, two switches are closed to short circuit the motor winding and immediately initiate flow of a current therethrough;
• and as soon as the current flow reaches a predetermined magnitude, the switches are turned off, whereby a winding voltage rises to above the bus voltage and a generated current is pumped back to the capacitor.