Question

The motor is connected to a 270 V de source through a H-bridge converter controlled using unipolar switching scheme. The converters operate at 10kHz switching frequency without a filter.

a) Build the circuit required for unipolar switching scheme. Simulate the H-bridge and the motor only (without speed and current controller), for rated speed and 50% rated speed at rated load torque. Sketch the current and speed for 300 ms. Also sketch the carrier, reference, and actual armature voltage for three switching cycles.

Answer 1

To implement the unipolar switching scheme for the H-bridge converter, four power switches are needed. LTspice or PLECS can be used to simulate the H-bridge and the motor's behavior at rated speed and 50% rated speed. The simulation can show the current, speed, carrier, reference, and actual armature voltage waveforms.

Step-by-step explanation:

To build the circuit required for the unipolar switching scheme, you will need an H-bridge converter. This converter consists of four power switches that can be either transistors or semiconductor devices like MOSFETs or IGBTs. The H-bridge is controlled by a microcontroller or a gate driver to switch the power devices appropriately and generate the desired waveform for the motor's operation. Without a filter, the switching frequency of the converter is set at 10kHz.

For the simulation, you can use software like LTspice or PLECS to model the H-bridge and the motor. The rated speed and load torque will determine the required voltage and current in the simulation. You can then plot the current and speed of the motor for 300ms to visualize their behavior at rated speed and 50% rated speed. Additionally, you can plot the carrier, reference, and actual armature voltage for three switching cycles to analyze the voltage waveforms.