SJDE-01APA

SJDE-02APA

SJDE-04APA

SJDE-04APA+SJME-04AMB41

SJDE-08APA

SJME-01AMA41

SJME-04AMA41

SJME-04AWA41

SJME-08AWA41

The inverter consists of three half-bridge units where the upper and lower switch are controlled complimentarily, meaning when the upper one is turned on, the lower one must be turned off, and vice versa. As the power device’s turn-off time is longer than its turn-on time, some dead time must be inserted between the time one transistor of the half-bridge is turned off and its complementary device is turned on. The output voltage is mostly created by a Pulse Width Modulation (PWM) technique, where an isosceles triangle carrier wave is compared with a fundamental-frequency sine modulating wave. The natural points of intersection determine the switching points of the power devices of a half-bridge inverter. This technique is shown in Figure 3-6. The 3 -phase voltage waves are shifted 120o to one another and thus a 3-phase motor can be supplied

The most popular power devices for motor control applications are Power MOSFETs and IGBTs. A Power MOSFET is a voltage-controlled transistor. It is designed for high-frequency operation and has a low-voltage drop, so it has low power losses. However, saturation temperature sensitivity limits the MOSFET’s use in high-power applications. An Insulated-Gate Bipolar Transistor (IGBT) is controlled by a MOSFET on its base. The IGBT requires low drive current, has fast switching time, and is suitable for high switching frequencies. The disadvantage is the higher voltage drop of the bipolar transistor, causing higher conduction losses.

Vector control is the most popular control technique of AC induction motors. In special reference frames, the expression for the electromagnetic torque of the smooth-air-gap machine is similar to the expression for the torque of the separately excited DC machine. In the case of induction machines, the control is usually performed in the reference frame (d-q) attached to the rotor flux space vector. That’s why the implementation of vector control requires information on the modulus and the space angle (position) of the rotor flux space vector. The stator currents of the induction machine are separated into flux- and torque-producing components by utilizing transformation to the d-q coordinate system, whose direct axis (d) is aligned with the rotor flux space vector. That means that the q-axis component of the rotor flux space vector is always zero: