A thyristor starter is configured to accelerate 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 of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.

A thyristor starter is configured to accelerate 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 of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.

A connecting device for motor and supply network is provided, comprising: a Variable Frequency Drive (VFD), a first switch (S.sub.1) and a second switch (S.sub.2), wherein the Variable Frequency Drive (VFD) is connected in series to the first switch (S.sub.1), and the second switch (S.sub.2) is connected in parallel to the series circuit composed of the Variable Frequency Drive (VFD) and the first switch (S.sub.1). The connecting device of the invention further comprises a bidirectional Silicon Controlled Rectifier (SCR) or two anti-parallel single-directional Silicon Controlled Rectifiers (SCR1,SCR2), wherein the bidirectional Silicon Controlled Rectifier (SCR) or the two anti-parallel single-directional Silicon Controlled Rectifiers (SCR1,SCR2) is/are connected in parallel to the second switch (S.sub.2). The connecting device of the present invention would not be subject to high current surge when VFD bypassing, avoids the high cost for the overrating of the cable and the bypassing switch, and is easy to be implemented.

A connecting device for motor and supply network is provided, comprising: a Variable Frequency Drive (VFD), a first switch (S.sub.1) and a second switch (S.sub.2), wherein the Variable Frequency Drive (VFD) is connected in series to the first switch (S.sub.1), and the second switch (S.sub.2) is connected in parallel to the series circuit composed of the Variable Frequency Drive (VFD) and the first switch (S.sub.1). The connecting device of the invention further comprises a bidirectional Silicon Controlled Rectifier (SCR) or two anti-parallel single-directional Silicon Controlled Rectifiers (SCR1,SCR2), wherein the bidirectional Silicon Controlled Rectifier (SCR) or the two anti-parallel single-directional Silicon Controlled Rectifiers (SCR1,SCR2) is/are connected in parallel to the second switch (S.sub.2). The connecting device of the present invention would not be subject to high current surge when VFD bypassing, avoids the high cost for the overrating of the cable and the bypassing switch, and is easy to be implemented.

An inverter system for a vehicle includes: an energy storage device configured to store electrical energy, a first inverter including a plurality of first switching elements and configured to convert the electrical energy stored in the energy storage device into alternating-current (AC) electric power, a second inverter including a plurality of second switching elements different from the plurality of first switching elements, a motor configured to be driven by receiving the AC power converted by the first inverter and the second inverter, current sensors disposed between the first inverter and the motor and the second inverters and the motor, respectively, and configured to detect a current input to the motor, and a controller configured to generate a pulse width modulation (PWM) signal for controlling driving of the motor.

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 current sourced control topology is provided for an AC motor controller that eliminates many of the problems associated with prior art motor controllers that use voltage source inverter (VSI) technologies. By controlling the output of AC current sources such as synchronously controlled down converters to directly drive each motor phase, significant efficiency gains and a reduction in electromagnetic interference is achievable.

This invention provides a frequency converter and bypass frequency conversion control system, and its switching control method, belonging to the technical field of motor drive control. The frequency converter of this invention accesses a network voltage signal with a corresponding first frequency and first phase, wherein the frequency converter is configured to be able to operate in tracking and synchronization mode, and in tracking and synchronization mode, the frequency converter tracks the first frequency and first phase of the network voltage signal in order to basically synchronize the second frequency and second phase of its output voltage signal with the first frequency and corresponding first phase of the network voltage signal. The frequency converter of this invention achieves simple, low cost, fast synchronization with good synchronism.

This invention provides a frequency converter and bypass frequency conversion control system, and its switching control method, belonging to the technical field of motor drive control. The frequency converter of this invention accesses a network voltage signal with a corresponding first frequency and first phase, wherein the frequency converter is configured to be able to operate in tracking and synchronization mode, and in tracking and synchronization mode, the frequency converter tracks the first frequency and first phase of the network voltage signal in order to basically synchronize the second frequency and second phase of its output voltage signal with the first frequency and corresponding first phase of the network voltage signal. The frequency converter of this invention achieves simple, low cost, fast synchronization with good synchronism.

A thyristor starter is configured to accelerate 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 of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.