Reverse rotation prevention in centrifugal compressor

A controller to operate a heat exchanger system following receipt of a shutdown command, the controller being configured to:

• position inlet guide vanes (IGVs) of a compressor in a first position in the event of at least one of:
• a first precondition being in effect;
• and
• the first and a second precondition both not being in effect;
• position the IGVs in a second position in an event the first precondition is not in effect but the second precondition is in effect;
• ramp a speed of the compressor down until a third precondition takes effect;
• remove power from a motor configured to drive the compressor;
• and
• position the IGVs in the first position once power is removed from the motor.

A heat exchanger system, comprising:

• a compressor comprising inlet guide vanes (IGVs) at an inlet thereof;
• a motor configured to drive the compressor;
• and
• a controller,
• wherein the controller is configured to control the compressor, the IGVs and the motor and, upon receipt of a shutdown command, positions the IGVs in a first position in the event of at least one of a first precondition being in effect and the first and a second precondition both not being in effect, positions the IGVs in a second position in an event the first precondition is not in effect but the second precondition is in effect, ramps a speed of the compressor down until a third precondition takes effect, removes power from the motor and positions the IGVs in the first position once power is removed from the motor.