Power converter lab manual by chaturvedula

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
A
Lab Manual
On
POWER CONVERTERS LAB
By
U P KUMAR CHATURVEDULA, M.Tech (PhD), MIEEE
Associate Professor, EEE
M.TECH –POWER ELECTRONICS AND DRIVES

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING PAGE 2
LIST OF EXPERIMENTS
S. No Name of the Experiments
1
SINGLE PHASE HALF WAVE CONTROLLED CONVERTER WITH RESISTIVE-
INDUCTIVE LOAD
2
SINGLE PHASE FULLY CONTROLLED CONVERTER WITH RESISTIVE-
INDUCTIVE LOAD
3
SPEED CONTROL OF 3-PHASE SLIP RING (WOUND ROTOR) INDUCTION
MOTOR
4
THYRISTORISED DRIVE FOR DC MOTOR WITH CLOSED LOOP CONTROL
5
THYRISTORISED DRIVE FOR PMDC MOTOR WITH SPEED MEASUREMENT &
CLOSED LOOP CONTROL
6
SPEED MEASUREMENT OF PMDC MOTOR WITH CLOSED LOOP CONTROL
7
IGBT USING SINGLE 4 QUADRANT CHOPPER DRIVE FOR PMDC MOTOR
WITH SPEED MEASUREMENT AND CLOSED LOOP AND CONTROL
8
SINGLE PHASE CYCLO CONVERTER BASED AC INDUCTION MOTOR
CONTROLLER
9
THREE PHASE INPUT THYRISTORISED DRIVE 3HP DC MOTOR WITH CLOSED
LOOP CONTROL
10
THREE PHASE INPUT IGBT DRIVE FOR 4 QUADRANT CHOPPER OF 3HP DC
MOTOR WITH CLOSED LOOP CONTROL

SINGLE PHASE HALF WAVE CONTROLLED CONVERTER
WITH RESISTIVE-INDUCTIVE LOAD
Expt No:
Date:
Aim:
To design single phase half wave controlled converter with resistive-
inductive load and verify the output waveforms by assembling the circuit.
Apparatus required:
1. Single phase half wave controlled converter kit
2. Patch chords
3. CRO
4. Voltmeter (0-30V)
Circuit diagram:
Pulse generator
A1
G1
R
Vo
K1
L
Io
1
2
Is
Single Phase half wave controlled converter
Vs
SCR-1
24V AC supply
Connection Procedure:
1. Connect G1K1 of firing circuit to G1K1 of SCR-1
2. Connect P terminal of 24V AC input to anode A1 of SCR-1
3. Connect N terminal of 24V AC input to RL load
4. Connect Cathode K1 of SCR-1 to RL load

5. Connect voltmeter across resistor and inductor.
6. Connect CRO probe across the RL load
Experimental procedure:
1. Switch on the CRO
2. Switch on the kit
3. Note down the peak value of AC input voltage Vm,triggering
angle  and conduction angle 
4. Adjust the firing angle gradually and note down output DC
voltage.
5. Calculate output DC voltage
6. Plot the Vm vs Angle (Triggering angle and conduction angle)
Model calculation:
As in the case of a resistive load, the thyristor T becomes forward
biased when the supply voltage becomes positive at ωt = 0. However, it does
not start conduction until a gate pulse is applied at ωt = α. As the thyristor
turns ON at ωt = α the input voltage appears across the load and the load
current starts building up. However, unlike a resistive load, the load current
does not become zero at ωt = π, instead it continues to flow through the
thyristor and the negative supply voltage appears across the load forcing the
load current to decrease. Finally, at ωt = β (β > π) the load current becomes
zero and the thyristor undergoes reverse recovery.

From this point onwards the thyristor starts blocking the supply
voltage and the load voltage remains zero until the thyristor is turned ON
again in the next cycle. It is to be noted that the value of β depends on the
load parameters. Therefore, unlike the resistive load the average and RMS
output voltage depends on the load parameters. Since the thyristors does not
conduct over the entire input supply cycle this mode of operation is called the
“discontinuous conduction mode”.
However, I
ORMS
can not be obtained from V
ORMS
directly. For that a
closed from expression for i
0
will be required. The value of β in terms of the
circuit parameters can also be found from the expression of i
0
.

Tabular form:
S.No Triggering Angle Calculated output
voltage
Measured
output voltage
1.
2.
3.
4.
5.

Model output waveforms:
Result:
Thus the single phase half wave controlled converter is designed and
the output waveforms are plotted.

SINGLE PHASE FULLY CONTROLLED CONVERTER WITH
RESISTIVE-INDUCTIVE LOAD
Expt No:
Date:
Aim:
To design single phase fully controlled converter with resistive-
inductive load and verify the output waveforms by assembling the circuit.
Apparatus required:
1. Single phase fully controlled converter kit
2. Patch chords
3. CRO
4. Voltmeter (0-30V)
Circuit diagram:
Is
K1
G3
G1
G1
L
R
G2
G3
Pulse Generator
G4
A1
G4
T3
G2
A3
Single phase fully controlled converter with Resistive-Inductive Load
A2
T2
A4
T4
K4 K2
Vm
sinwt(24V
Ac supply)
T1
V0
Io
K3

Connection Procedure:
5. Connect P terminal of 24V AC input to anode A1 of SCR-1
6. Connect N terminal of 24V AC input to anode A3of SCR-3
7. Connect Cathode K1 of SCR-1 to cathode K3 of SCR-3
8. Connect Anode A4 of SCR-4 to anode A2 of SCR-2
9. Connect Anode A1 of SCR-1 to cathode of K2 of SCR-2
10.Connect load Resistor and inductor across the terminals SCR-1
cathode and supply –ve terminal
11.Connect voltmeter across resistor and inductor.
12.Connect CRO probe across the RL load
Experimental procedure:
1. Switch on the CRO
2. Switch on the kit
3. Note down the peak value of AC input voltage Vm,triggering
angle  and conduction angle 
4. Adjust the firing angle gradually and note down output DC
voltage.
5. Calculate output DC voltage
6. Plot the Vm vs Angle (Triggering angle and conduction angle)
Model calculation:

The circuit diagram of a single phase fully controlled bridge converter
is shown in figure. It is one of the most popular converter circuits and is
widely used in the speed control of Dc machines. The single phase fully
controlled bridge converter is obtained by replacing all the diode of the
corresponding uncontrolled converter by thyristors. Thyristors T
1
and T
2
are
fired together while T
3
and T
4
are fired 180º after T
1
and T
2
.
From the circuit diagram of Fig (a) it is clear that for any load current
to flow at least one thyristor from the top group (T
1
, T
3
) and one thyristor
from the bottom group (T
2
, T
4
) must conduct. It can also be argued that
neither T
1
T
3
nor T
2
T
4
can conduct simultaneously.
For example whenever T
3
and T
4
are in the forward blocking state and
a gate pulse is applied to them, they turn ON and at the same time a
negative voltage is applied across T
1
and T
2
commutating them immediately.
Similar argument holds for T
1
and T
2
. For the same reason T
1
T
4
or T
2
T
3
can
not conduct simultaneously. Therefore, the only possible conduction modes
when the current i
0
can flow are T
1
T
2
and T
3
T
4
. Of coarse it is possible that at
a given moment none of the thyristors conduct.
This situation will typically occur when the load current becomes zero
in between the firings of T
1
T
2
and T
3
T
4
. Once the load current becomes zero
all thyristors remain off. In this mode the load current remains zero.

Consequently the converter is said to be operating in the discontinuous
conduction mode. Fig (b) shows the voltage across different devices and the
dc output voltage during each of these conduction modes.
It is to be noted that whenever T
1
and T
2
conducts, the voltage across
T
3
and T
4
becomes –v
i
. Therefore T
3
and T
4
can be fired only when v
i
is
negative i.e, over the negative half cycle of the input supply voltage.
Similarly T
1
and T
2
can be fired only over the positive half cycle of the input
supply. The voltage across the devices when none of the thyristors conduct
depends on the off state impedance of each device. The values listed in Fig
(b) assume identical devices.
Under normal operating condition of the converter the load current
may or may not remain zero over some interval of the input voltage cycle. If
i
0
is always greater than zero then the converter is said to be operating in the
continuous conduction mode. In this mode of operation of the converter T
1
T
2
and T
3
T
4
conducts for alternate half cycle of the input supply.
However, in the discontinuous conduction mode none of the thyristors
conduct over some portion of the input cycle. The load current remains zero
during that period.
Model calculation:

Tabular form:
S.No Triggering Angle Calculated
output voltage
Measured
output voltage
1.
2.
3.
4.
5.
Model output waveforms:
Result:
Thus the single phase fully controlled converter is designed and the
output waveforms are plotted.

SPEED CONTROL OF 3-PHASE SLIP RING (WOUND ROTOR)
INDUCTION MOTOR
Expt No:
Date:
Aim:
To control the speed of a 3- phase slip ring induction motor using
Rotor resistance inverter Module and study the motor performance under No
load and Load condition.
Apparatus required:
S.NO Name of the Apparatus Range Type Qty
1. Voltmeter 0-200V MI 1
2. Ammeter 0-10A MI 1
3. Inverter module 3,5HP, 200V,10A - 1
4. Slip ring induction motor 5HP,10A,1000rpm Wound rotor 1
5. Tachometer 0-10000rpm Analog 1
6. Rheostat 200/2A Wire Wound 1
Circuit Diagram:
R
L
A
O
A
Speed control of three phase wound rotor Induction motor
Y
D
Ex.
R
V
B
3 Phase
Auto
Transformer

A
A
L
O
Stator R=200
ohms/2A
B
D
R
Ex.
R
Rotor
V
Speed control of three phase wound rotor Induction motor
Y
200V,3 phase Isolation Transformer
Theory:
The synchronous speed of a 3 phase induction motor can be changed
either by changing the frequency, a) variable frequency source must be
available or by changing the no of poles where there must be provision to do
so, on the winding of the motors. The speed control can also be achieved by
variation of an external rotor resistance method.
Procedure:
1. Fuse rating is taken as 5% of full load current.
2. The range of all meters selected according to the rating of the
motor.
Under NO Load:
1. Circuit connections are made as shown in figure.
2. Keeping the frequency control knob of the inverter in the minimum
position, the TPSTS is closed.
3. The inverter is operated over the full range available and the
speed, voltage, frequency and current are recorded for every 5Hz
increase in the frequency.
4. Then inverter control knob is brought to minimum position and the
TPSTS is opened.
5. The graphs of f Vs V, f Vs N, f Vs stator current are plotted.

System under Load:
1. The fuse rating is chosed as 120% of the full load current.
2. Circuit connections are made as shown in figure. The centre Zero
DC ammeter is placed between two rotor terminals.
3. Keeping the frequency control knob of the inverter in the minimum
position, the TPSTS is closed.
4. The machine is brought to a speed of about 1000rpm using the
inverter (frequency knob).
5. The machine is load gradually using the brake drum arrangement.
As the load increases from minimum to maximum the two spring
balance readings, stator line current, rotor current and the rotor
frequency are noted. The TPSTS is opened.
6. The graphs of Torque Vs rotor current, Torque Vs rotor frequency
and Torque Vs stator current are plotted.
Rotor frequency measurement:
1. The centre Zero ammeter will oscillate at rotor frequency. It can be
calculated by observing the time for 10 oscillations. T= Time for 10
oscillations.
Rotor frequency, fr =10/T Hz.
Formulae used:
Torque = 9.81 R (S1 S2) Nm
R = r (t/2) m
Where, Rotor= effective radius of brake drum.
Model graph:

PROCEDURE:
1. Power circuit connections are made as shown in the circuit diagram
.connect three phase input to the three phase auto transformer or
directly to the three phase load. The output of the autotransformer
terminals are connected to the respective R,Y & B stator terminals of
three phase wound rotor induction motor .The rotor terminals of the
three phase wound rotor induction motor is connected to the three
phase input of respective R,Y & B terminals of three phase wound rotor
induction motor power circuit consists of diode rectifier and a load
resistance
2. Connect the rheostat load ammeter and voltmeter to suitable points
3. Check all the connections and confirm connections made are correct
before switching on the equipments
4. Keeping auto transformer at minimum position switch on the rectifier
circuit to rotor using three phase MCB
5. Now switch on three phase mains supply
6. Increase the autotransformer voltage slowly for suitable value such
that motor rotates
7. Note down voltage V and current I in the meters
8. Calculate resistance R =V/I
9. do experiment for different resistance values by varying rheostat and
note down corresponding rpm
10. Plot a graph of load resistance against speed

Tabulation
S.No
Frequency
F(Hz)
Rotor
current
Is(A)
Rotor
voltage
V(v)
Speed
N(rpm)
Rotor
Resistance
R=V/I 
Results:

THYRISTORISED DRIVE FOR DC MOTOR WITH CLOSED
LOOP CONTROL
Expt No:
Date:
Aim:
To control the speed of the 1HP DC motor using Thryistorised Drive for
Closed Loop control.
Apparatus:
1. Voltmeter 0-200V MC 1
2. Ammeter 0-5A MC 1
3. Thyristorised Drive Control
with Closed loop control
1HP, 200V,5A - 1
4. DC Shunt Motor 1HP,5A,1500rpm shunt 1
6. Rheostat 360/1.2A Wire Wound 1
7. CRO - - 1
Theory:
Rectifier converts AC supply to DC Supply with thyristor , variable DC
supply 0V to maximum can be obtained from a fixed AC source by triggering
( Turning ON ) SCR i.e by applying gate current to the SCR at any desired
instant when the SCR is applied with positive voltage to anode. Unlike diode ,
SCR can block the forward voltage when gate current is not supplied .Hence
converters using SCR’s are termed as controlled rectifier .Normally for DC
power Requirement such as in DC drives single phase full wave half
controlled rectifier are used.

Circuit Diagram:
Ra
230V AC
Supply
FF
La
A
AA
T2
DF
A
RR
T1
1 5
4 8
1HP DC
shunt
Motor
T1
Field
Vs
V
D3
D1
D1
D2
360
ohms/1.2A
230V AC
Supply
D4
D2
F
R
Vs
(0-30V)
Thyristorised Drive for 1HP DC shunt motor with Speed
Measurement & Closed loop control
T1
1 5
4 8
(0-2A)
Eb
Single Phase Half Controlled Bridge with Motor Loads
When the single phase semi- converter is connected with R-L/Motor
load a freewheeling diode must be connected across the load. During positive
half cycle T1 is forward biased &b T1 is fired at wt= . the load is connected
to the input supply through T1 and D1 during period wt  .During the
period from wt(+) ,the input voltage is negative and free wheeling
diode Df is forward biased ,Df conducts to provide the continuity of current in
the inductive load. The load current is transferred from T1 and D1 to Df , and
thyristor T1 and D1 are turned off at wt =  .During negative half cycle of
input voltage , thyristor T2 is forward biased and the firing of T2 at wt=(+)
will reverse bias Df is turned off and the load connected to the supply
through T2 and D2

When the load is inductive and T1 is triggered first it will conduct with
D1 to pass current through load. When the supply voltage is negative, load
emf will drive current through T1D2. This is an exponentially decreasing
current .When the new negative half cycle begins T1 is in conduction and it
would keep on conducting with D1 as if triggered at wt=0 .In this case load
may not receive the DC power. To ensure proper operation at the beginning
of positive half cycle T2 has to be turned off and similarly T1 should be turned
off when negative half cycle begins .This is achieved by the freewheeling
diode.
This conversion has better power factor due to free wheeling diode.
For R-L load with freewheeling diode the average output voltage can
be found from
Procedure:-
 Connect DC motor and armature terminals to respective points
in the power circuit and speed sensor to feedback terminals
socket. Connect the voltmeter and ammeter to the respective
points
 Circuit connections are made as shown in the circuit diagram
 Check the connections and conform the connections made are
correct before switching on mains supply
 Keeping all the knobs at minimum positions
 Keeping PID switches ON ( down ward) position
 Switch on the field supply to the motor
 Switch on the firing controller POWER supply switch
 Switch on the power circuit .Single phase auto transformer may
be used set the voltage slowly or to avoid sudden surge of
current
 Set the rpm to suitable value through the KNOB SET PRM ( Say
1000 rpm
 Using P,I,D Knobs adjust the running rpm to set rpm by varying
P gain , I timing ,D gain

 Load the motor up to 3-4A load .Note down the speed for
different loads. Observe the current and voltage waveforms
using CPO
 Slowly reduce the load set rpm to minimum value ,reduce
autotransformer voltage, switch Off MCB , Switch off the
triggering circuit ,switch off field supply and remove the
connections
TABULATION:
No Load: S1=0 S2=0
S.No Set RPM No Load Voltage
(VL)
No Load Current
(IL)
Speed in RPM
With Load
S.No
Load in Grams Load Voltage
(VL)
Load Current
(IL)
Speed in RPM
S1 S2
Results:

THYRISTORISED DRIVE FOR PMDC MOTOR WITH SPEED
MEASUREMENT & CLOSED LOOP CONTROL
Expt No:
Date:
Aim:
To Control the speed of the PMDC motor using thyristorised converter
with P, PI and PID controller.
Apparatus:
2. Ammeter 0-0.5A MC 1
3. Thyristorised converter
unit PMDC Module
P,PI,PID
controller
- 1
4. PMDC Motor 12V,0.5HP,1A,
1500rpm
Wound rotor 1
5. CRO - - 1
6. RPS 0-30V Dual 1
Circuit Diagram:
D1
T1
1 5
4 8
Thyristorised Drive for PMDC motor with Speed
Measurement & Closed loop control
Eb
T1
A
(0-30V)
Vs
T2
DF
D2
PMDC
MOTOR
La
(0-2A)
V
230V AC
Supply
Ra

Theory:-
(turning ON) SCR i.e by applying gate current to the SCR at any desired
instant when the SCR is applied with positive voltage to anode. Unlike diode,
power requirement such as in DC drives single phase full controlled rectifier
are used.
Single Phase Half Controlled Bridge with Motor Loads:
When the single phase semi-converter is connected with R-L / Motor
half cycle T1 is forward biased & T1 is fired at wt =  the load is connected to
the input supply through T1 and D1 during period wt .During the period
from wt(+), the input voltage is negative and free wheeling diode Df is
forward biased , DF conducts to provide the continuity of current in the
inductive load. The load current is transferred from T1 and D1 to DF &
thyristor T1 and D1 are turned off at wt = .During negative half cycle of
input voltage , thyristor T2 is forward biased , and the firing of T2 at wt = +
will reverse bias DF .the diode DF is turned off and the load connected to the
supply through T2 and D2.
When the load is inductive and T1 is triggered, first it will conduct with
D1 to pass current through load. When the supply voltage is negative , load
emf will drive current through T1D2 .This is an exponentially decreasing
current .when the new negative half cycle begins T1 is in conduction and it
would keep on conducting with D1 as if triggered at wt=0 . In this case load
cycle T2 has to be turned off and similarly T1 should be turned off when
negative half cycle begins .this is achieved by the freewheeling diode.
This conversion has better power factor due to free wheeling diode
For R-L load with freewheeling diode the average output voltage can be
found from

Vdc(av)=(1/)  

Vm Sin d
= Vm/(-Cos)

Vdc(av)= Vm/(1+Cos)
Procedure:
1. Connect PMDC motor to respective points in the power circuit and
speed sensor to feedback terminals socket. Connect the voltmeter and
ammeter to the respective points
2. Circuit connections are made as shown in the circuit diagram
3. Check the connections and confirm the connections made are correct
before switching on mains supply
4. Keeping all the knobs at minimum position
5. Keeping PID switches ON ( down ward) position
6. Switch on the POWER supply switch
7. Set the rpm to suitable value through the knob SET RPM(say 1000
rpm)
8. Using P, I , D knobs adjust the running rpm by varying P gain , I
timing , D gain
9. Load the motor up to 250 grams load in steps of 50 grams . Note
down the speed for different loads. Observe the current and voltage
waveforms using CRO
10.Slowly reduce the DC voltage to zero , switch off the unit and remove
the connections
Tabulation:
P Controller:
Set RPM =
S.No Load in Grams Load Voltage (VL)v Load Current IL A Speed in rpm
1.
2.
3.
4.

PI Controller:
Set RPM =
1.
2.
3.
4.
PID Controller:
Set RPM =
1.
2.
3.
4.
Results:-

SPEED MEASUREMENT OF PMDC MOTOR WITH CLOSED LOOP
CONTROL
Expt No:
Date:
Aim:
To Control the speed of the PMDC motor using P, PI and PID controller
with closed loop control.
Apparatus:
2. Ammeter 0-0.5A MC 1
3. P,PI,PID controller of
PMDC Module
P,PI,PID
controller
- 1
1500rpm
Wound rotor 1
5. CRO - - 1
6. RPS 0-30V Dual 1
Circuit Diagram:
DF
230V AC
Supply
Speed Measurement of PMDC Motor with Closed Loop
Control using MOSFET Chopper
T1
1 5
4 8
S
La
Eb
D1
G
D3 Firing
cicuit
(0-2A)
V
D4
D
Ra
PMDC
MOTOR
A
D2
30V Regulated Power Supply
(0-30V)
Vs

Theory:-
(turning ON) SCR i.e by applying gate current to the SCR at any desired
instant when the SCR is applied with positive voltage to anode. Unlike diode,
power requirement such as in DC drives single phase full controlled rectifier
are used.
Single Phase Half Controlled Bridge with Motor Loads:
When the single phase semi-converter is connected with R-L / Motor
half cycle T1 is forward biased & T1 is fired at wt =  the load is connected to
the input supply through T1 and D1 during period wt .During the period
from wt(+), the input voltage is negative and free wheeling diode Df is
forward biased , DF conducts to provide the continuity of current in the
inductive load. The load current is transferred from T1 and D1 to DF &
thyristor T1 and D1 are turned off at wt = .During negative half cycle of
input voltage , thyristor T2 is forward biased , and the firing of T2 at wt = +
will reverse bias DF .the diode DF is turned off and the load connected to the
supply through T2 and D2.
When the load is inductive and T1 is triggered, first it will conduct with
D1 to pass current through load. When the supply voltage is negative , load
emf will drive current through T1D2 .This is an exponentially decreasing
current .when the new negative half cycle begins T1 is in conduction and it
would keep on conducting with D1 as if triggered at wt=0 . In this case load
cycle T2 has to be turned off and similarly T1 should be turned off when
negative half cycle begins .this is achieved by the freewheeling diode.
This conversion has better power factor due to free wheeling diode
For R-L load with freewheeling diode the average output voltage can be
found from

Vdc(av)=(1/)  

Vm Sin d
= Vm/(-Cos)

Vdc(av)= Vm/(1+Cos)
Procedure:
1. Connect PMDC motor to respective points in the power circuit and
speed sensor to feedback terminals socket. Connect the voltmeter and
ammeter to the respective points
2. Circuit connections are made as shown in the circuit diagram
3. Check the connections and confirm the connections made are correct
before switching on mains supply
4. Keeping all the knobs at minimum position
5. Keeping PID switches ON ( down ward) position
6. Switch on the POWER supply switch
7. Set the rpm to suitable value through the knob SET RPM(say 1000
rpm)
8. Using P, I , D knobs adjust the running rpm by varying P gain , I
timing , D gain
9. Load the motor up to 250 grams load in steps of 50 grams . Note
down the speed for different loads. Observe the current and voltage
waveforms using CRO
10.Slowly reduce the DC voltage to zero , switch off the unit and remove
the connections
Tabulation:
P Controller:
Set RPM =
1.
2.
3.
4.

PI Controller:
Set RPM =
1.
2.
3.
4.
PID Controller:
Set RPM =
1.
2.
3.
4.
Results:-

IGBT USING SINGLE 4 QUADRANT CHOPPER DRIVE FOR PMDC MOTOR WITH
SPEED MEASUREMENT AND CLOSED LOOP AND CONTROL
Expt No:
Date:
Aim:
To Control the speed of the PMDC motor for forward and Reverse with
P, PI and PID controller and closed loop control using IGBT single 4 quadrant
chopper drive.
Apparatus:
1. Voltmeter 0-30V MI 1
2. Ammeter 0-1A MI 1
3. IGBT single 4 quadrant
chopper drive of PMDC
Module
- P,PI,PID
controller
1
1500rpm
Wound rotor 1
5. CRO - - 1
6. RPS 0-30V Dual 1
CH4 OPERATED
CH1 CH2,CH3 OFF
REVERSE
REGENERATIVE
BRAKING
CH3 OPERATED
CH1,CH4 ,CH2
OFF REVERSE
MOTORING
CH2 OPERATED
CH1,CH4, CH3
OFF FORWARD
REGENERATIVE
BRAKING
IL
+VL
-VL
CH1 OPERATED
CH2,CH3 OFF CH4
ON FORWARD
MOTORING
IL
-
+
FOUR QUADRANT OPERATION

Theory:
Chopper Converts fixed DC Voltage to Variable DC Voltage through the
use of semiconductor devices .The DC to Dc Converters have gained
popularity in modern industry .Some practical applications of DC to DC
Converters include armature Voltage control of DC motors converting one DC
voltage level to another level, and controlling DC power for wide variety of
industrial processes .The time ratio controller (TRC) is a from of control for
DC to DC conversion
In four quadrant DC chopper drives a motor can be made to work in
forward motoring mode (first quadrant) , forward regenerative breaking
mode ( Second quadrant) , Reverse motoring mode ( third quadrant) and
reverse regenerative breaking mode( fourth quadrant) .The circuit shown
offers four quadrant operation of a DC motor . Its operation in the four
quadrants can be explained as follows.
Forward Motoring Mode ( I quadrant)
During this mode or first quadrant operation, chopper CH2,CH3 are
kept off , CH4 is kepr on whereas CH1 is operated. When CH1,CH4 are on ,
motor voltage is positive and positive armature current rises .when CH1 is
turned off , positive armature current free wheels and decreases as it flows
through CH4,D2. In this manner controlled operation in first quadrant is
obtained
Forward Regenerative Breaking Mode (II Quadrant)
A DC Motor can work in the regenerative breaking mode only if motor
generated emf is made to exceed the DC source voltage. For obtaining this
mode CH1, CH3 and CH4 are kept off where as CH2 is operated .when CH2 is
turned on , negative armature current rises through CH2,D4,EA ,lA,Ra .When
CH2 is turned off, diodes D1,D4 are turned on and the motor acting as a
generator returning energy to Dc source .This results in forward regenerative
breaking mode in the second quadrant.

Reverse Motoring Mode ( III Quadrant)
This operating mode is opposite to forward motoring mode. Chopper
CH1,CH4 are kept off , CH2 is kept on where as CH3 is operated .When CH3
& CH2 are on , armature gets connected to source voltage Vs so that both
armature voltage and armature current ia is negative .As armature current is
reversed , motor torque reversed and consequently motoring mode in third
quadrant is obtained. When CH3 is turned off , negative armature current
freewheels through CH2 ,D4,Ea,La & Ra ; armature current decreases and
thus speed control is obtained in third quadrant
Reverse Regenerative Breaking Mode ( IV Quadrant)
As in forward braking mode , reverse regenerative braking mode is
feasible only if motor generated emf is made to exceed the source voltage
.For this operating mode CH1,CH2 & CH3 are kept off whereas CH4 is
operated .When CH4 is turned on , positive armature current ia rises through
CH4, D2,Ra, La & Ea .when CH4 is turned off , diodes D2 ,D3 begin to conduct
and motor acting as generator returns energy to Dc source, This leads to
reverse regenerative braking operation of the DC separately excited Motor in
fourth quadrant.
Circuit diagram:
Ph
La
4 Quadrant Chopper Drive for PMDC Motor
-
(0-0.5)A
CH2
Vs
CH4
230V AC
Supply
CH3
G4
N
Ra
io=ia=IL
IL
D1
Eb
-
G2
CH1
(0-30) V
D4
D1
D3
G1
PMDC MOTOR
D4
D2
A
T1
1 5
4 8
D2
+
G3
V
-
VL
+
+
D3

PROCEDURE:
1. Connect motor terminals to respective points in the power circuit &
speed sensor to feedback terminals socket. Connect the voltmeter
& ammeter to the respective points.
2. Circuit connections are made as shown in the circuit diagram.
3. Connect suitable DC voltage using regulated 30V/1A power supply.
4. Check the connections and confirm the connections made are
correct before switching on mains supply & DC power supply.
5. Keeping all the knobs at minimum position switch on the DC power
supply adjust the DC voltage to say 12V. (12V to 15V)
6. Keeping PID switches ON position.
7. Keep the FM/RM switch to upward position for forward rotation.
8. Set the rpm to suitable value through the knob (with in 1000 rpm).
9. Using P, I, D knobs adjust the running rpm to set rpm.
10.Load the motor up to 250 grams load in steps of 50 grams. Note
down the speed for different loads. Observe the current & voltage
waveforms using CRO four chopper operations.
11.Slowly reduce the DC voltage to zero. Change the FM/RM switch to
downward position, do the above procedure for the reverse
rotation.
Tabulation:
Forward Rotation
P Controller:
Set RPM =
1.
2.
3.
4.

PI Controller:
Set RPM =
1.
2.
3.
4.
PID Controller:
Set RPM =
1.
2.
3.
4.
Reverse Rotation
P Controller:
Set RPM =
1.
2.
3.
4.
PI Controller:
Set RPM =
1.
2.
3.
4.

PID Controller:
Set RPM =
1.
2.
3.
4.
Results:-

SINGLE PHASE CYCLO CONVERTER BASED AC INDUCTION
MOTOR CONTROLLER
Expt No:
Date:
Aim:
To construct a single phase cycloconverter circuit and to study
its performance.
APPARATUS:
1. Single Phase Cyclo
Converter Power Circuit
with Firing Circuit
0.5HP,5A,115V - 1
2. Rheostat 200 , 2A Wire Wound 1
3. Isolation Transformer 230V/115-0-
115V
Step down 1
4. Single Phase Induction
Motor
0.5HP
Squirrel Cage 1
5. CRO - - 1
6. Patch Cards - - -
THEORY:
A cycloconverter converts input power at one frequency to output
power at a different frequency with one stage conversion. Cycloconverter is
used in speed control of high power AC drives, induction heating etc. The
experimental circuit shown is for obtaining a single phase frequency divided
output from a single phase AC input. One group of SCR’s produces positive
polarity load voltage and other group produces negative half cycle of the
output.

CIRCUIT DIAGRAM:
T1
G4
V
G2
0
G1
T3
V
Ex.LOAD
V
C2
G3
0
C3
C1
V
MCB
Single Phase Cyclo Converter Power Circuit
C4
T2
T4
C4
1
T4
C3
2
T3
T4
150
180
T1
G2
90
60
T2
T3
V
G4
T2
G3
C3
G4
Single Phase Cyclo Converter
AC Input Supply
120
V
C1
3
Frequency Division
G1
V C1
G1
C2
G2
Firing Angle
Isolation
Transformer 230
V/115 V-0 V-115 V
C2
G3
30
C4
V
0
0
0
Single Phase IM
T1

SCR’s T1 and T3 of the positive group are gated together depending on
the polarity of the input, only one of them will conduct. when upper AC
terminal is positive with respect to O, SCR T1 will conduct, and when upper
AC terminal is negative, SCR T3 will conduct thus in both half cycles of input,
the load voltage polarity will be positive by changing firing angle, the
duration of conducting of each SCR (and there by the magnitude of the
output voltage) can be varied. For the sake of simplicity it is assumed that
the load is positive. Then each SCR will have a conduction angle of ( -) and
turn off by natural commutation at the end of every half cycle of the input. At
the end of each half period of the output, the firing pulses to the SCR’s of the
positive group will be stopped and SCR’s T2 and T4 of the negative group will
be fired.
PROCEDURE:
SINGLE PHASE CYCLOCONVERTER
 The connections are made as shown in the circuit of single phase cyclo
converter with R load (100 Ohm/2A) or motor load with divided by 1
frequency using suitable isolation transformer.
 The gate cathode terminals of the thyristors are connected to the
respective points on the firing circuit.
 Check all the connections and confirm connections made are correct
before switching on the equipments.
 Switch ON power supply & triggering circuit.
 The output wave forms are seen on a CRO.
 The firing angle is varied and AC output voltage across the load is
noted.
 Repeat the above procedure for divided by two frequency.

Tabular Column:
Frequency Division: 1 Frequency Division: 2
S.No
Firing
Angle

Speed in
RPM
S.No
Firing
Angle

Speed in
RPM
Result:

THREE PHASE INPUT THYRISTORISED DRIVE 3HP DC MOTOR WITH
CLOSED LOOP CONTROL
Expt No:
Date:
Aim:
To construct a three phase fully controlled full wave bridge rectifier
and to control speed of the DC motor.
Apparatus:
3. Three Phase Thyristorised
Drive Control with Closed
loop control
1HP, 200V,5A - 1
7. CRO - - 1
THEORY:
In the bridge rectifier all the three arms of SCR’s are connected as
control switches. This is called fully controlled bridge converter. Depending
on the delay angle, the output current can be either continuous or
discontinuous. In fully controlled rectifier the load voltage may be positive or
negative for inductive loads. The power circuit & the control circuits are
provided with the manual.

Circuit Diagram:
D4
(0-200V)
C6
D2
Y
C2
G4
T4
1 5
4 8
T1
B
G1
C3
A
T2
Three Phase Isolation Transformer
G3
DF
T1
G5
T3
G6
A
T3
G4
T5
360
ohms/1.2A
Y/Y Connection
T5
G6
V
Eb
C1
T4
G2
D3
T2
T3
1 5
4 8
Three Phase Firing
Circuit
Field
T6
AA
230V AC
Supply
T4
1HP DC
shunt
Motor
Three Phase Input Thyristorised Drive 3Hp DC Motor With Closed Loop Control
(0-5)A
FF
T6
Vs
A1
C1
C2 RR
La
A2
Ra
C3
G3
T1
1 5
4 8
R
T2
1 5
4 8
Ph
C5
G5
G1
C4
F
N
C4
R
D1
C6
G2
C5

PROCEDURE:
1. Connect motor terminals (field & armature) to respective points in
the power circuit & speed sensor to feedback terminals socket.
2. Circuit connections are made as shown in the circuit diagram. Use
3P auto transformer.
3. Connect 3 pin power cards from power unit (rectifier) to the mains
supply.
4. Switch on the field supply of the motor.
5. Keeping PID switches at ON position, keep all knobs at minimum
position now switch on the firing unit.
6. Switch on the three phase power input.
7. Switch on the Power Circuit through MCB.
8. Adjust the gains of PID knobs (say maximum).
9. Set the rpm through the knob slowly (say 900 rpm). By slowly
increasing auto transformer voltage.
10. Load the motor up to 3/4 Amp load. Note down the speed for
different loads.
11. Release the load slowly. Bring the set rpm knob to minimum
position slowly & all the knobs at minimum position.
12.Switch off power circuit by MCB, switch off firing circuit, and switch
off field supply & remove the connections.
TABULATION:
No Load: S1=0 S2=0
(VL)
No Load Current
(IL)
Speed in RPM

With Load
S.No
(VL)
Load Current
(IL)
Speed in RPM
S1 S2
Results:

THREE PHASE INPUT IGBT DRIVE FOR 4 QUADRANT CHOPPER OF
3HP DC MOTOR WITH CLOSED LOOP CONTROL
Expt No:
Date:
Aim:
To construct a three phase fed closed loop four quadrant chopper drive
circuit and to control the speed of the separately - excited DC motor.
Apparatus:
3. Three Phase IGBT Drive
Control with Closed loop
control
1HP, 200V,5A - 1
7. CRO - - 1
THEORY:
Chopper converts fixed DC voltage to variable DC voltage through the
use of semiconductor devices. The DC to DC converters have gained
popularity in modern industry. Some practical applications of DC to DC
converter include armature voltage control of DC motors converting one DC
voltage level to another level, and controlling DC power for wide variety of
industrial processes. The time ratio controller (TRC) is a form of control for
DC to DC conversion. In four quadrant DC chopper drives, a motor can be
made to work in forward - motoring mode (first quadrant), forward
regenerative breaking mode (second quadrant), reverse motoring mode
(third quadrant) and reverse regenerative breaking mode (fourth quadrant).

The circuit shown offers four quadrant operation of a separately -
excited dc motor. This circuit consists of three phase fed diode rectifier, four
choppers, four diodes and a separately - excited dc motor. Its operation in
the four quadrants can be explained as under.
Forward motoring mode (I quadrant):
During this mode or first - quadrant operation, chopper CH2, CH3 are
kept off, CH4 is kept on whereas CH1 is operated. When CH1, CH4 are on,
motor voltage is positive and positive armature current rises. When CH1 is
turned off, positive armature current free-wheels and decreases at it flows
through CH4, D2. In this manner controlled operation in first quadrant is
obtained.
Forward regenerative braking mode (II quadrant):
A dc motor can work in the regenerative-breaking mode only if motor
generated EMF is made to exceed the dc source voltage. For obtaining this
mode CH1, CH3 and CH4 are kept off whereas CH2 is operated. When CH2 is
turned on, negative armature current rises through CH2, D4, Ea, La, ra.
When CH2 is turned off, diodes D1, D4 are turned on and the motor acting as
a generator returning energy to dc source. This result in forward
regenerative-breaking mode in the second-quadrant.
Reverse motoring mode (III quadrant):
This operating mode is opposite to forward motoring mode. Chopper
CH1, CH4 are kept off, CH2 is kept on whereas CH3 is operated. When CH3
and CH2 are on, armature gets connected to source voltage Vs so that both
armature voltage and armature current ia is negative. As armature current is
reversed, motor torque reversed and consequently motoring mode in third
quadrant is obtained. When CH3 is turned off, negative armature current
freewheels through CH2, D4, Ea, La, ra; armature current decreases and
thus speed control is obtained in third quadrant. Note that during this mode
polarity of Ea is opposite to that shown in fig.
Reverse Regenerative-braking mode:
As in forward breaking mode, reverse regenerative-breaking mode is feasible
only if motor generated EMF is made to exceed the source voltage.

For this operating mode, CH1, CH2 and CH3 are kept off whereas CH4
is operated. When CH4 is turned on, positive armature current ia rises
through CH4, D2, ra, La, Ea. When CH4 is turned off, diodes D2, D3 begin to
conduct and motor acting as generator returns energy to dc source. This
leads to reverse regenerative-breaking operation of the dc separately excited
motor in fourth quadrant.
If the gain of the P controller is less then the error voltage (difference
between set & running) is more. If the gain is increased the error voltage is
reduced. The I controller further reduces the error. If the timing of I
controller is increased almost all the error is reduced. However the D
controller has negligible effect on overall system.
PROCEDURE:
 Connect motor terminals (field & armature) to respective points in the
power circuit & speed sensor to feedback terminals socket.
 Circuit connections are made as shown in the circuit diagram using
three phase auto transformer & three phase isolation transformer.
 Keeping FM/RM at released position for forward rotation & pressed
position for reverse rotation of the motor.
 Connect 3 pin power cards from power unit (rectifier) to the mains
supply.
 Switch on the field supply of the motor.
 Keeping auto transformer at minimum position, switch on the three
phase power input.
 Switch on the Power Circuit through MCB.
 Keeping PID ON switch on the firing unit.
 Set the rpm through the knob (say 1000 rpm).
 Adjust the auto transformer for suitable voltage, maximum 70%.
 Adjust the gains of P, I, D knobs..
 Load the motor up to 1 A load. Note down the speed for
different loads.
 Remove the load, reduce the set speed knob to minimum position,

reduce auto transformer voltage to minimum value. Switch off power
circuit by MCB, Switch off three phase mains supply, switch off firing
circuit, switch off field supply & remove the connections.
 The above experiment may be repeated for the reverse rotation of the
motor.
TABULATION:
Forward Motoring:
No Load: S1=0 S2=0
(VL)
No Load Current
(IL)
Speed in RPM
With Load
S.No
(VL)
Load Current
(IL)
Speed in RPM
S1 S2
Reverse Motoring:
No Load: S1=0 S2=0
(VL)
No Load Current
(IL)
Speed in RPM

With Load
S.No
(VL)
Load Current
(IL)
Speed in RPM
S1 S2
Results:

3Hp DC SHUNT MOTOR
D4
T1
1 5
4 8
(0-200)V
3- Phase Input IGBTfor 4 Quadrant Chopper Drive for 3HP DC
Shunt Motor with Closed Loop Control
+
D1
V
G3
CH2
RR
+
G4
Three Phase Rectifier
Ph
G1
CH4
D2
Y/Y Connection
230V AC
Supply
-
VL
D2
La
-
A
D1
Eb
Three
Phase
Auto
Transformer
360
ohms/1.2A
D1
D3
D3
+
D5
T3
1 5
4 8
CH3
Vs
G2
D4
Ra
R
D3
D4
D6
T2
1 5
4 8
IL
Y
-
R
D2
(0-0.5)A
B
io=ia=IL
F
T4
1 5
4 8
CH1
N
Three
Phase
Input
Voltage
Source
FF

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