In a variable speed generator/motor device including a variable frequency power converter, a direct current voltage device including a voltage type self-excited converter, an automatic voltage adjuster, and a converter current adjuster that controls unit converters, a first three-phase branch circuit is provided between the direct current voltage device and an alternating current system; a second three-phase branch circuit is provided between the variable frequency power converter and a three-phase squirrel-cage induction machine; a first load switch is provided between the first three-phase branch circuit and the second three-phase branch circuit; a measurement current transformer is provided between the three-phase squirrel-cage induction machine and the second three-phase branch circuit.

Monitoring conditions of an electric motor using stator current and voltage signals from power supplied to the motor is disclosed herein. The stator voltage and current signals may be used to calculate instantaneous power values which may be used to calculate slip. The slip may be used to monitor for a locked rotor condition during startup of the motor. The slip value may be used to provide thermal protection to the electric motor.

Monitoring conditions of an electric motor using stator current and voltage signals from power supplied to the motor is disclosed herein. The stator voltage and current signals may be used to calculate instantaneous power values which may be used to calculate slip. The slip may be used to monitor for a locked rotor condition during startup of the motor. The slip value may be used to provide thermal protection to the electric motor.

In a variable speed generator-motor apparatus, a power converter includes six two-terminal arms each formed by serially connecting k unit converters that can output arbitrary voltage, an AC rotating electric machine includes an armature winding with 60-degree phase zone formed from a double layer coil, the armature winding being divided into first and second pole sides to form double star connection by binding neutral points and to be drawn out as two sets of three-phase terminals; three-phase terminals on the first pole side are connected to first terminals of three arms, and second terminals of the three arms are star-connected to a first terminal of a DC power supply; three-phase terminals on the second pole side are connected to second terminals of remaining three arms, and first terminals of the three arms are star-connected to a second terminal of the DC power supply.

In a variable speed generator-motor apparatus, a power converter includes six two-terminal arms each formed by serially connecting k unit converters that can output arbitrary voltage, an AC rotating electric machine includes an armature winding with 60-degree phase zone formed from a double layer coil, the armature winding being divided into first and second pole sides to form double star connection by binding neutral points and to be drawn out as two sets of three-phase terminals; three-phase terminals on the first pole side are connected to first terminals of three arms, and second terminals of the three arms are star-connected to a first terminal of a DC power supply; three-phase terminals on the second pole side are connected to second terminals of remaining three arms, and first terminals of the three arms are star-connected to a second terminal of the DC power supply.

A PM line-start motor, preferably motors having a power of at least 5 kW, and a switch-on method therefor are provided. The motor includes a rotor and a stator having a stator winding designed as a pole-reversible rotary field winding. With the aid of the pole-reversible rotary field winding, the regenerative braking torque generated during the asynchronous high-run operation can be avoided, preferably by use of a sequence controller to control the changeover of the pole-reversible rotary field winding in the run-up phase.

As a configuration of carrying out a turning operation of a brushless synchronous power generation apparatus, there are provided a synchronous generator, an AC exciter, a rotary rectifier attached to an armature of the AC exciter, and short-circuiting means which three-phase short-circuits armature windings of the AC exciter, wherein the armature windings of the AC exciter are short-circuited, causing the AC exciter to operate as an induction motor, thus rotating the rotor shaft of the synchronous generator.

As a configuration of carrying out a turning operation of a brushless synchronous power generation apparatus, there are provided a synchronous generator, an AC exciter, a rotary rectifier attached to an armature of the AC exciter, and short-circuiting means which three-phase short-circuits armature windings of the AC exciter, wherein the armature windings of the AC exciter are short-circuited, causing the AC exciter to operate as an induction motor, thus rotating the rotor shaft of the synchronous generator.

A rotor for an LSIPM comprises a plurality of permanent magnets defining a number of poles (P) of the LSIPM, and a plurality of rotor bars spaced about the rotor defining a rotor bar area (BA). The rotor bars are formed of a conductive material having an associated conductivity (.sub.RB). End members are disposed on axial opposite ends of the rotor core. The end members are in electrical contact with the rotor bars. The end members are formed from a material having an associated conductivity (.sub.EM). Each end ring member has a minimum geometric cross sectional area (ERA) and outer diameter that generally corresponds to the rotor core outer diameter. The ERA is greater than 0.5 times the rotor bar area per the number of poles (BA/P) times a ratio of the rotor bar material conductivity to the end member material conductivity (.sub.RB/.sub.EM).

A rotor for an LSIPM comprises a plurality of permanent magnets defining a number of poles (P) of the LSIPM, and a plurality of rotor bars spaced about the rotor defining a rotor bar area (BA). The rotor bars are formed of a conductive material having an associated conductivity (.sub.RB). End members are disposed on axial opposite ends of the rotor core. The end members are in electrical contact with the rotor bars. The end members are formed from a material having an associated conductivity (.sub.EM). Each end ring member has a minimum geometric cross sectional area (ERA) and outer diameter that generally corresponds to the rotor core outer diameter. The ERA is greater than 0.5 times the rotor bar area per the number of poles (BA/P) times a ratio of the rotor bar material conductivity to the end member material conductivity (.sub.RB/.sub.EM).