written 8.8 years ago by | modified 3.2 years ago by |
Mumbai University > Electronics Engineering > Sem7 > Power Electronics 2
Marks: 10M
written 8.8 years ago by | modified 3.2 years ago by |
Mumbai University > Electronics Engineering > Sem7 > Power Electronics 2
Marks: 10M
written 8.8 years ago by | • modified 8.8 years ago |
A separately excited dc motor, fed through single phase half wave converter, is shown in Figure (a) Motor field circuit is fed through a single phase semi converter in order to reduce the ripple content in the field circuit. Single phase half wave converter feeding a dc motor offers one quadrant drive, Figure (b)
The waveforms for source voltage Vs , armature terminal voltage Vt , armature current ia , source current is and freewheeling diode current ifd are sketched in Fig (c) . Note that thyristor current iT=is . The armature current is assumed ripple free.
For single phase half wave converter , average output voltage of converter, Vo = armature terminal voltage, Vt
V0=Vt=Vm2π(1+cosα1)for 0<α1<π
Where Vm = maximum value of source voltage
For single phase semi converter in the field circuit, the average output voltage is given as Vf
Vf=Vmπ(1+cosα2)for 0<α2<π
It is seen from the waveforms of fig 12.7 (c) that
rms value of armature current, Iar=Ia
rms value of source or thyristor current
Iαt=√I2απ−α2π=Iα(π−α2π)1/2
5) rms value of freewheeling diode current,
Ifdr=√I2απ+α2π=Iα(π+α2π)1/2
6) Apparent input power = ( rms source voltage)*(rms source current) =VsIsr
7) Power delivered to motor = EaIa+I2a∗ra=(Ea+Iara)Ia=Vt∗Ia
8) Input supply pf = pf=EaIa+I2araVa.Isr=Vt.IaVa.Isr