Method and apparatus for controlling a brushless DC motor

A control apparatus for a brushless DC motor which has a permanent magnet rotor and a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comprising:

• a plurality of first comparison circuits, one provided for each phase, for comparing a specified reference voltage with the stator winding terminal voltages;
• a circuit detecting rotor position in response to the first comparison circuits, based on induced voltages generated in the stator windings which are non-conducting when the motor is rotated, the circuit switching conduction to each stator winding in response to detection of the rotor position;
• a conduction circuit for selectively supplying a first conduction pattern in which all the stator windings take higher voltages than the specified reference voltage and a second conduction pattern in which all the windings take a lower voltage than the specified reference voltage while the rotor is stopped;
• a second comparison circuit for comparing a reference output determined for each conduction pattern and the output of the first comparison circuits when the conduction circuit is supplying the first and second conduction patterns;
• and
• an abnormality detection circuit for detecting abnormalities based on the comparison results of the second comparison circuit.

A control apparatus for a brushless DC motor which has a permanent magnet rotor and a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comprising:

• a plurality of first comparison circuits, one provided for each phase, for comparing a specified reference voltage with the stator winding terminal voltages;
• a second comparison circuit comparing comparison outputs of the first comparison circuits with a reference signal;
• a circuit for detecting rotor position in response to the second comparison circuit, based on induced voltages generated in the stator windings which are non-conducting when the motor is rotated, the circuit switching conduction to each stator winding in response to detection of the rotor position;
• a conduction circuit for supplying multiple conduction patterns in which windings of one phase or two phases are at lower voltages than a specified reference voltage and a remaining stator winding is at a higher voltage than the specified reference voltage while the motor is stopped;
• a third comparison circuit for comparing a reference output determined for the conduction patterns with the output of the second comparison circuit when the conduction circuit is conducting;
• and
• an abnormality detection circuit for detecting abnormalities based on the comparison results of the third comparison circuit.

A control apparatus for a brushless DC motor which has a permanent magnet rotor and a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comprising:

• a plurality of first comparison circuits, one provided for each phase, which compare a specified reference voltage with the stator winding terminal voltages;
• a circuit which detects rotor position in response to the first comparison circuits, based on induced voltages generated in the stator windings which are non-conducting when the motor is rotated, the circuit switching conduction to each stator winding in response to detection of the rotor position;
• a conduction circuit which supplies multiple conduction patterns in which windings of one phase or two phases are at lower voltages than a specified reference voltage and a remaining phase stator winding is a higher voltage than the reference voltage while the brushless motor is stopped;
• a second comparison circuit which compares a reference output determined for the conduction pattern and the outputs of the first comparison circuits during conduction by the conduction circuit;
• and
• an abnormality detection circuit which detects abnormalities in response to the comparison results of the second comparison circuit.

An air conditioner having a sealed compressor and a compressor motor, which is built into the sealed compressor, having a permanent magnet rotor and a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comprising:

• a plurality of first comparison circuits, one provided for each phase, for comparing a specified reference voltage with the stator winding terminal voltages;
• a circuit for detecting rotor position in response to the first comparison circuits based on induced voltages generated in the stator windings which are non-conducting when the motor is rotated, the circuit switching conduction to each stator winding in response to detection of the rotor position;
• a conduction circuit for supplying a specific conduction pattern to each stator winding when the rotor is stopped;
• a second comparison circuit which compares a reference output determined for the conduction pattern with the outputs of the first comparison circuits when the conduction circuit is conducting;
• and
• an abnormality detection circuit which detects abnormalities based on the comparison results of the second comparison circuit.

An air conditioner having a sealed compressor and a compressor motor, which is built into the sealed compressor, having a permanent magnet rotor and a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comprising:

• a plurality of first comparison circuits, one provided for each phase, for comparing a specified reference voltage with the stator winding terminal voltages;
• a second comparison circuit comparing comparison outputs of the first comparison circuits with reference signal;
• a circuit for detecting rotor position in response to the second comparison circuit, based on induced voltages generated in the stator windings which are non-conducting when the motor is rotated, the circuit switching conduction to each stator winding in response to detection of the rotor position;
• a conduction circuit for supplying multiple conduction patterns in which windings of one phase or two phases are at lower voltages than a specified reference voltage and a remaining stator winding is at a higher voltage than the specified reference voltage while the motor is stopped;
• a third comparison circuit for comparing a reference output determined for the conduction patterns with the output of the second comparison circuit when the conduction circuit is conducting;
• and
• an abnormality detection circuit for detecting abnormalities based on the comparison results of the third comparison circuit.

A method for controlling a brushless DC motor which has a permanent magnet rotor, a 3-phase stator winding for applying a rotating magnetic field to the permanent magnet rotor, comparison circuits, one for each phase, which compare a specified reference voltage with the stator winding terminal voltages, a circuit which detects rotor position based on the outputs of the comparison circuits and an inverter circuit which switches conduction to each stator winding in accordance with the detected rotor position, comprising the steps of:

• detecting abnormalities based on the outputs of the comparison circuits;
• outputting a specified frequency and voltage from the inverter in a state in which connection between the stator windings and the inverter is broken when an abnormality is detected in the detecting step;
• measuring output inter-phase voltages of the inverter when the connection is broken;
• and
• determining an abnormality of the comparison circuits when the inter-phase voltages obtained by the measuring step are approximately the same value, and determining an abnormality of the inverter otherwise.