Lesson -13 - nptelwith thyristors. Control over the output dc voltage is obtained by controlling the
conduction interval of each thyristor. This method is known as phase control and
..... commutation of the outgoing thyristor it is essential that this interval is larger
than the turn off .... 13.4 Gate Drive circuit for three phase fully controlled
converter.Module 2 - nptelA gate turn-off thyristor (GTO) also may be used, in which case, it may be turned
off by applying a short negative pulse to its gate, but is turned on by a short
positive .... If mth pulse starts at and its width is m t? = ? m ? , the average output
voltage due to p number of pulses is found as. ( ) m m m p dc m 1. 2. V. 2Vsin t d
t? ? +?.LINE COMMUTATED CONVERTERSalso commutated in a similar manner because the gate is ineffective to achieve
commutation. The reverse voltage that serves to turn OFF a thyristor or diode is
called the commutating voltage. We can turn OFF a thyristor by injecting a
reverse bias across it and "force" it to turn OFF. For example, if the converter is a
rectifier, ...dc motor control using chopper - ethesis@nitr - NIT RourkelaResults 6 - 20 ... cathode-gate voltage which in turn induces the forward current to fall and the
GTO switch off. GTO thyristors suffer from long switch off times, whereby after the
.... 4. Ra is the armature resistance in ohms. 5. La is the armature inductance in
Henry. Now the torque equation will be given by: Td = Jd?/dt +B?+TL.
