A permanent magnet synchronous motor includes at least two series-connected windings for each phase, and is configured to be driven by selecting the windings using a multi-inverter driving device configured to switch between an inverter for low-speed drive and an inverter for high-speed drive. A ratio of an induced voltage constant of at least one group of windings constituting the windings for the high-speed drive and a d-axis inductance is larger than a ratio of an induced voltage constant of all the series-connected windings to the d-axis inductance.

A method for starting a drive motor. The drive motor includes a motor stator with stator coils and a motor rotor, and a control electronics system and a power electronics system which supply power to the stator coils with a predefined coil voltage and a predefined constant start-up rotation frequency to generate a rotating field to drive the motor rotor. The method includes supplying power to at least one stator coil with a coil voltage corresponding to a start value, increasing the coil voltage in steps, monitoring an electric current flowing through the power electronics system, and, when a specific minimum voltage drop is detected, terminating the increasing of the coil voltage in steps, and performing a safety increase of the coil voltage by increasing a start-up voltage value by a predefined safety value to a first operating voltage value where the motor rotor is drivable in an unregulated mode.

A method for starting a drive motor. The drive motor includes a motor stator with stator coils and a motor rotor, and a control electronics system and a power electronics system which supply power to the stator coils with a predefined coil voltage and a predefined constant start-up rotation frequency to generate a rotating field to drive the motor rotor. The method includes supplying power to at least one stator coil with a coil voltage corresponding to a start value, increasing the coil voltage in steps, monitoring an electric current flowing through the power electronics system, and, when a specific minimum voltage drop is detected, terminating the increasing of the coil voltage in steps, and performing a safety increase of the coil voltage by increasing a start-up voltage value by a predefined safety value to a first operating voltage value where the motor rotor is drivable in an unregulated mode.

At least one example embodiment discloses a method of controlling an alternating current (ac) machine. The method includes determining or retrieving a current limit for the ac machine, determining a characterized peak current value based on a voltage-to-speed ratio of the ac machine, determining current command values for the ac machine based on at least one of the torque command limit and a torque command for the ac machine, determining current command values for the ac machine based on the torque command limit and controlling the ac machine based on the current command values.

A method is for a network synchronization of a permanently excited three-phase machine including a soft starter, including thyristors, and mechanical bypass contacts for bridging the thyristors in the network operation. The method includes generating a first control signal, to initiate switching the mechanical bypass contacts to become conductive, after a criterion is reached while running up the three-phase machine on the soft starter, a time at which the first control signal is generated representing actuation time of the bypass contacts; generating ignition pulses for the thyristors within a time period, running from the actuation time to a contact time of the bypass contacts, using a second control signal; and operating the three-phase machine in the network operation via the bypass contacts. Each ignition pulse for a thyristor is generated when a phase current measurement indicates that the current strength in the assigned phase has fallen below a threshold value.

A method is for a network synchronization of a permanently excited three-phase machine including a soft starter, including thyristors, and mechanical bypass contacts for bridging the thyristors in the network operation. The method includes generating a first control signal, to initiate switching the mechanical bypass contacts to become conductive, after a criterion is reached while running up the three-phase machine on the soft starter, a time at which the first control signal is generated representing actuation time of the bypass contacts; generating ignition pulses for the thyristors within a time period, running from the actuation time to a contact time of the bypass contacts, using a second control signal; and operating the three-phase machine in the network operation via the bypass contacts. Each ignition pulse for a thyristor is generated when a phase current measurement indicates that the current strength in the assigned phase has fallen below a threshold value.

A motor driving controller, comprising a rotary position detection device generating a position detection signal corresponding to a rotary position of a rotor of a motor; a control circuit selecting a first driving control signal for performing rectangular wave driving or a second driving control signal for performing driving with an overlapped energization period longer than an overlapped energization period in the rectangular wave driving, based on the position detection signal, thereby to output a driving control signal; and a motor driver outputting a driving signal to a stator coil of the motor based on the driving control signal, wherein the control circuit outputs the first driving control signal at time of starting, and the control circuit outputs the second driving control signal when a rotary state is detected on the basis of the position detection signal.

A thyristor starter accelerates a synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter by intermittently setting DC output current to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. A second controller controls the firing phase of a thyristor in a converter such that DC output current of the converter matches a current command value, based on a detection signal of a position detector. In the first mode, the current command value is set such that the current value is higher as the rotation speed of the synchronous machine is higher.

A thyristor starter accelerates a synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter by intermittently setting DC output current to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. A second controller controls the firing phase of a thyristor in a converter such that DC output current of the converter matches a current command value, based on a detection signal of a position detector. In the first mode, the current command value is set such that the current value is higher as the rotation speed of the synchronous machine is higher.

An electric motor (10) has a stator (20) having a number S of stator poles (21, 22, 23, 24, 25, 26); a rotor (40) having a rotor magnet (40′), which rotor magnet (40′) has a number R of rotor poles (41, 42, 43, 44, 45, 46), R being equal to S, and the rotor (40) or the stator (20), or both, exhibiting a magnetic asymmetry. The asymmetry facilitates startup. The electric motor has a single-phase winding arrangement (30) with first (11), second (12) and third (13) terminals. Current can be made to flow, selectively, from either the first or the second terminal, through certain coils, to the third terminal (13). There is an output stage (50), preferably an H-bridge. The W total coils comprise a plurality of subgroups (TG1, TG2) of coils. A method for current flow through an electric motor utilizes these sub-groups (TG1, TG2) for current flow.