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Theoretical syllabus
Week
Regenrating fully controlled interters , examples , dc motor speed control.
𝟏𝒔𝒕
Three face inverters , output voltage wave from with , triggering pulses and
equations.
𝟐𝒏𝒅
Thyristor protection from the high rate change in current and voltage ,
protection from the transient change in source voltage , fully protection circuit
from all possible faults due to current and voltage .
𝟑𝒓𝒅
Dc to ac inverters methods of forcing the thyristor to get off .
𝟒𝒕𝒉
Parallel and senies inverter, single and three phase , control mdthods in
charging frequency and voltage , output wave forms1 .
𝟓𝒕𝒉
Inverter application , emergency power supply , single phase dc motor speed
control.
𝟔𝒕𝒉
Three phase motor control by using a constant ratio of variation frequency and
voltage.
𝟕𝒕𝒉
Choppers , dc to dc inverter frequency constant , line constant .
𝟖𝒕𝒉
Types of choppers , dc motor speed control .
𝟗𝒕𝒉
Ac to ac inverter , single phase voltage requlator , three phase voltage requlator
.
𝟏𝟎𝒕𝒉
General application on single and three induction motor speed control due to
the change in stat or voltage , using the closed loop feedback circuit to control
the dlippery rings of ac motor .
𝟏𝟏𝒕𝒉
Cyclic inverter , ac to dc cyclic inverter , dc to dc cyclic inverter
𝟏𝟐𝒕𝒉
Ac to ac cyclic inverter control black diagram .
𝟏𝟑𝒕𝒉
Using amplitude modulation for speed control.
𝟏𝟒𝒕𝒉
Using polar transistor for ac motor speed control .
𝟏𝟓𝒕𝒉
Fully controlled full wave Rectifier
: -
2Vm
Vd.c = g cos
If α >= 90°
Vd.c = 2Vm cos 120= –Vm
g g
EX:- if L =50 mH , R= 10 Ω , α=30° , V= 325 sin 100
π
t Calculate :-
1- Vd.c
2-
the angle of the load (Ф)
3-
time to commutate the SCR
4-
Discuss the waveform of (I load )
Solution :-
Vd.c = Vo = ∫α^(π+α) Vmsin(wt)d(wt) = (2 Vm)/π cosα
Vd.c = (2*325 )/π cos30° = 179.2 v
tanФ =WL/R
Ф = tan- 1 (100π*50*10-3)/10 = 57.5°
Wtq = β = π – α
tq = (π- α)/w = (π- (π/6))/100π = 8.3 msec
ﺎﻣﺑﺔﯾ ﻣﺣﻟ(Ф) ﺑﻛﺔﯾ ﯾﺧﺄﺗﻟ(α) ﺎﻓﺎﯾﺗﻣﺣﻟﻛﯾﻣﺗﺳﻣ
Converter Control of DC Machines
The speed of a dc motor can be controlled by controlling the dc voltage across its
armature terminals. A
phase controlled thyristor converter can provide this dc voltage source. For a low- power drive, a single-
phase bridge converter can be used ,whereas for a high-power drive, a three- phase bridge circuit is
preferred. The machine can be a permanent magnet or wound field type. The wound field type permits
variation and
reversal
of field and is normally preferred in large power machines.
DC Motor Drives:-
The DC drive is relatively simple and cheap (compared to induction motor
drives). But DC
motor itself is more expensive.
•
Due to the numerous disadvantages of DC motor (esp. maintenance), it is
getting less
popular, particularly in high power applications.
•
For low power applications the cost of DC motor plus
drives is
still economical.
•
For servo application, DC drives is still popular because
of good
dynamic response and ease of control.
•
Future Trend? Not so bright prospect for DC, esp. in
high
power drives
.
Thyristor/SCR drives
Basic single-phase drive
Example
Consider a 500V, 10kW , 20A rated- DC motor with armature resistance of 1 ohm.
When supplied at 500V, the UNLOADED motor runs at 1040 rev/min, drawing a
current of 0.8A (ideally current is zero at no-load).
– Estimate the full load speed at rated values
– Estimate the no-load speed at 250V.
Solution:-
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