Magnetic bearing compressor protection

A vapor compression system, comprising:

• a condenser for transferring heat from a working fluid to an external fluid medium;
• a first compressor and a second compressor in fluid communication with the condenser, at least one of the first compressor and the second compressor comprising:
• an electric motor for driving a rotating shaft;
• a magnetic bearing for levitating the rotating shaft when in an active mode, the magnetic bearing disposed adjacent to the electric motor;
• and
• a touchdown bearing configured to rotate and support the rotating shaft when the magnetic bearing is in an inactive mode, the touchdown bearing disposed adjacent to the rotating shaft;
• a check valve in fluid communication with the condenser and at least one of the first compressor and the second compressor;
• a controller configured to control at least one of the first compressor and the second compressor, the controller configured to receive a shutdown command for one of the first compressor and the second compressor, the controller in communication with at least one sensor disposed within the compressor in shutdown, the sensor configured to monitor at least one of a rotational speed of the rotating shaft and a differential pressure over the check valve for a preset time, wherein the controller maintains the magnetic bearing in the active mode at least during the preset time and further wherein the controller is configured to put the other of the first compressor or the second compressor into shutdown when the rotational speed or the differential pressure over the check valve for the preset time does not reach an acceptable threshold within the preset time;
• and
• an isolation valve positioned between an evaporator and the first compressor, the isolation valve configured to prevent flow of the working fluid into the first compressor
• wherein the isolation valve is in communication with the controller, the controller configured to close the isolation valve when the rotational speed of the rotating shaft of the first compressor does not reach the acceptable threshold within the preset time.