DC Motor Speed Control by Four Quadrant Chopper

LAP 4
DC motor speed control by four-quadrant chopper
NAI SOKNOV
E20170539
LECTURED BY:
LIM PHING
ENGINEERING’S DEGREE
DEPARTMENT OF ELECTRONIC AND ENERGY ENGINEERING
INSTITUTE OF TECHNOLOGY OF CAMBODIA
PHNOM PENH
2020-2021
DC motor speed control by four quadrant chopper
1. Objective
 Understand about the chopper and its classification
 Operation of each chopper class
 Understand the basic of PWM (pulse width modulation) generation
 Control speed of DC motor and its direction by four quadrant chopper both closed loop
and opened loop.
2. Experiment procedure
 Pulse width modulation (PMW)
1) Pulse width modulation (PWM) is the signal get from the comparison of two signal.
Figure 1 PWM signal
2) PWM is essential because it is the great way to control the amount of power
delivered to the load without dissipating any waste power. It is also used to control
the speed of the motor or the brightness of the LED and the most importantly is
controlling the electronic switch such as Thyristor, Transistor, or IGBT.
3) Generate PWM
 Create triangle signal and constant signal the compare to each other
 If 𝑉𝑑𝑐 ≥ 𝑉𝑡𝑟 PWM=1
 If 𝑉𝑑𝑐 < 𝑉𝑡𝑟 PWM =0
Figure 3 PWM generating
Figure 2 PWM signal
 Introduction to chopper
1) Chopper is DC-DC converter, that change fixed DC power to variable DC power
that can be adjusted to desire among.
2) According the changing the switch position, there are 5 classes of choppers.
3) Given the circuit and the operation of each class
 Class A
Figure 4 circuit of class A chopper

Figure 5 Wave form of class A chopper
 When chopper is ON, supply voltage V is connected to the load.

 When chopper is OFF, V is disconnected from the load then 𝑣𝑜 = 0, then the
current still flow in the same direction into FWD.
 Class A chopper is the first quadrant chopper.
 Class B chopper
Figure 6 Circuit of class B chopper

Figure 7 Wave form of class B chopper
 When the chopper is ON, E induct the current through L and R in a direction
opposite.
 During the chopper is ON the inductor L is storing the energy.
 When chopper is OFF, Diode conduct, and the energy that is stored in L is
return to the supply.
 Second quadrant chopper
 Class C chopper
Figure 8 the circuit of Class C chopper

Figure 9 Wave form of Class C chopper
 When CH1 is ON, load current is positive. The output voltage is equal to V
and the load receive the power from voltage source V.
 When CH1 is off, L discharge then push current to flow throw D2 in the
same direction with zero output voltage.
 When CH2 is triggered, the voltage E force current to flow in the opposite
direction throw L and CH2.
 When CH2 is OFF, the energy stores in L drive the current through D1 and
supply. The current become negative and 𝑣0 = 𝑉
 First and second quadrant chopper
 Class D chopper
Figure 10 circuit of Class D chopper

Figure 11 Wave form of Class D chopper
 When CH1 and CH2 is ON the same time, the output voltage 𝑣0 = 𝑉
and the current flow throw load is positive.
 When CH1 and CH2 is OFF the energy that store in L will push the
current to flow throw D3 and D2 to voltage source with the same
direction of current. 𝑣0 = −𝑉
 Average load voltage is negative if 𝑡𝑜𝑛 < 𝑡𝑜𝑓𝑓
 It is two quadrant Chopper
 Class E chopper
Figure 12 Circuit of Class E chopper
 When CH1 and CH4 are triggered, the current 𝑖0 flow in the positive
direction from CH1 to CH2 and 𝑣0 = 𝑉. First quadrant.
 When CH1 and CH4 are OFF the energy that is stored in L will push 𝑖0
through D2 and D3 in the same direction, but 𝑣0 = −𝑉. Fourth
quadrant.
 When CH2 and CH3 is ON, the current 𝑖0 flow in opposite direction and
𝑣0 = −𝑉. Third quadrant.
 When CH2 and CH3 is OFF the current will flow from D1 to D4 cross
the load, 𝑣0 = −𝑉. Second quadrant.
4) The chopper class E is given with a DC source 𝑉 = 240𝑉, a load consists a resistance
𝑅 = 1Ω, an inductance 𝐿 = 0.02𝐻, and a source 𝐸 = 50𝑉 in series
a. Construct the Chopper is Simulink.
Figure 13 Chopper class E in MATLAB Simulink
b. Verify the four-quadrant of this chopper

 First IGBT AND IGBT 3 is triggered
Figure 14 wave form of class E chopper
 CH1 and CH2 is ON, 𝑖0 > 0, 𝑣0 = 250. First quadrant.

 CH1 and CH2 is OFF, 𝑖0 > 0, 𝑣0 = −250 and 𝑣0 become zero
because nomore energy left in the inductor L. Fourth quadrant
 Second IGBT1 and IGBT2 are triggered
Figure 15 Wave form of class E chopper
 CH2 and CH3 is ON, 𝑖0 < 0, 𝑣0 = −250. Third quadrant.

 CH2 and CH3 is OFF, 𝑖0 < 0, 𝑣0 = 250. Second quadrant.
c. Find average voltage of first and third quadrant.

 First quadrant
𝑉𝑎𝑣𝑔 = 𝑉0 = 𝑑𝑉𝑠 = 0.3 × 240 = 72𝑉
𝑉0 − 𝑉𝐸 72 − 50
𝐼𝑎𝑣𝑔 = = = 22𝐴
𝑅 1
 Third quadrant
𝑉𝑎𝑣𝑔 = 𝑑𝑉𝑠 = −30 × 240 = −72𝑉
𝑉𝑎𝑣𝑔 − 𝑉𝐸 −72 − 50
𝐼𝑎𝑣𝑔 = = = −122𝐴
𝑅 1
 One directional speed control DC motor
1. To control one direction DC motor then class A and class B is able to use.
2. Build a circuit of chopper class A with a load separate excited DC machine in
Simulink.
Figure 16 circuit of class A chopper and separate excited DC machine
3. Complete the table

Duty cycle d 25% 50% 75% 99%
𝑉𝑟𝑚𝑠 (𝑉) 120 169.7 207.8 238.8
𝐼𝑟𝑚𝑠 (𝐴) 0.59 0.74 0.94 1.18
𝜔(rad/s) 56.76 115.6 174.4 230.9
Table 1: Result of voltage, current, speed of DC motor for class A chopper
 Bi-directional speed control of DC motor
1. Build a circuit of class E chopper with the same DC motor
Figure 17 class E chopper with DC motor
2. Complete the table

MotorMode CH1 D1 CH2 D2 CH3 D3 CH4 D4
Forward ON OFF OFF conduct OFF OFF ON OFF
Backward OFF OFF ON OFF ON OFF OFF conduct
3. Make a closed loop PI controller to control motor’s speed
Figure 18 PI controller with DC machine

Figure 19 before using controller Figure 20 after using controller
4. Calculate the RMS voltage and current

Target speed 𝑉𝑟𝑚𝑠 (𝑉) 𝐼𝑟𝑚𝑠 (𝐴)
1000 rpm 131.6 10.74
-1000 rpm 81.33 9.05
Using Simulink to measure
3. Conclusion
PWM signal get from the comparison of one signal to triangle signal. It is very important
for controlling the switch electronic, as well as controlling in the chopper circuit. Chopper
is DC-DC converter. Base on main classification there two type of chopper DC chopper
and AC link. If base on the position of switch, there are 5 classes. Chopper circuit play the
main for controlling the speed and the direction of the motor.

DC Motor Speed Control by Four Quadrant Chopper

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LAP 4

DC motor speed control by four-quadrant chopper

Figure 1 PWM signal

Figure 3 PWM generating

Figure 2 PWM signal

Figure 4 circuit of class A chopper

 When chopper is ON, supply voltage V is connected to the load.

Figure 6 Circuit of class B chopper

Figure 8 the circuit of Class C chopper

Figure 10 circuit of Class D chopper

Figure 12 Circuit of Class E chopper

Figure 13 Chopper class E in MATLAB Simulink

b. Verify the four-quadrant of this chopper

 CH1 and CH2 is ON, 𝑖0 > 0, 𝑣0 = 250. First quadrant.

Figure 15 Wave form of class E chopper

 CH2 and CH3 is ON, 𝑖0 < 0, 𝑣0 = −250. Third quadrant.

c. Find average voltage of first and third quadrant.

Figure 16 circuit of class A chopper and separate excited DC machine

3. Complete the table

2. Complete the table

3. Make a closed loop PI controller to control motor’s speed

Figure 18 PI controller with DC machine

4. Calculate the RMS voltage and current

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