VSI : Basic 2 Level Inverter

One of the most common variable speed drives is the Voltage Source Inverter which

can have the configuration shown in this picture. The front end is a diode rectifier,

transforming the fixed frequency fixed voltage supply into a DC voltage. The DC Link

consists of a capacitor bank in parallel with the DC bus.

The inverter has two IGBTS per phase.

With this configuration, two voltage levels can be applied on each motor phase: either

DC+ or DC-, resulting in a 2-level switching topology.

The output to the motor, the phase to phase voltage, has three levels.

For instance, if IGBT’s 1 and 4 are On, the line to line voltage between phases U and V

will be full positive DC bus.

There are redundant combinations when 1 and 2 or 4 and 6 are On: for both of them,

the line voltage UV is 0 volts.

If 6 and 2 are On, the line to line voltage UV will be the full negative DC bus.

Forbidden switching combinations 1 and 6 On or 2 and 4 On would result in a short

circuit of DC+ to DC-.

#screenrepairs #expensivetechnologyrepair #wirelesstechnology