Abstract:
Fractional horse power single phase induction motors have no starting torque of their own. As a
result, these motors are started by auxiliary methods. Now-a- days, single phase induction motors
having large horse power rating are also in use in rural areas and in industries. These large horse
.power single phase induction motors require medium size capacitors for their start and running
purpose. In this thesis static cycloconverter and inverter topologies have been proposed to perform
the function of capacitors. Static converters are used for conversion of ac and dc power to ac and
de having frequency, magnitude and phase other than supply voltage. Several of the conventional
static converters can replace the starting and running capacitors of single phase induction motors.
When sinusoidal supply is switched at every quarter cycle, switched waveform shifted by 90° can
be obtained. This waveform may be utilized in the starting purposes of large hp single phase.
motors. This would replace the bulky capacitorsotherwise required for starting these motors alid
may also serve the purpose of power factor and other type of controls of the motors .. The quarter . cycle switched waveform though fulfils the required phase shift, pulse width modulated switching
is proposed in the thesis for better harmonic performance of output waveform. Analysis and
implementation of the PWM phase shift circuit has been carried out and reported in this thesis to
justify the feasibility of using these circuitsin the practical field. It has been found by analysis that
over modulated sine PWM switched static cycloconverters provide necessary phase shift for motor
start and at the same time keep the low order harmonics of the phase shift circuit output voltage
within acceptable limit. Motor operation by the proposed circuits has not been studied in detail in
this thesis and left for future investigation ..
