are those which convert fixed dc voltage to variable ac output voltage and
are generated in the power electronic circuit due to the frequent turn-on and
turn-off of the semiconductor devices. Due to this disturbances in the circuit,
it causes fluctuations in the supply voltage, torque pulsations, low power
factor, , increase of losses, less efficiency, etc.
3. PWM Technique:
technique, a fixed dc voltage is applied to the inverter as a input and a
controlled ac output voltage is obtained by adjusting the ON and OFF period of
the inverter devices.
scheme, there is only one pulse per half cycle and the width of the pulse is
varied to control the inverter output voltage.
scheme, there are several pulses in each half cycle and the width of the pulse
is varied to control the inverter output voltage. This method permits reduction
in harmonic content up to low output voltage.
acts as a comparator, which compares the carrier triangular signal and a dc
7. Pulse Generator:
generates trigger pulses/firing pulses; in order to turn-on the switching/power
8. Voltage source inverter:
the input dc voltage remains constant at low input impedance irrespective of ac
voltage delivered to load.
9. Utility Factor:
It is the
ratio of power delivered by the three-phase inverter when the load is 3-ϕ balanced to
the total power rating of all switching devices of the bridges.
10. Current source inverter:
the input dc current from the dc source is maintained at an effectively
constant level at high input impedance irrespective of load.