Three Phase Controlled Rectifier Circuit for Characteristic Control

in DC Shunt Motor

Anggara Trisna Nugraha

, Rachma Prilian Eviningsih

, Gramandha Wega Intyanto

Salsabila Ika Yuniza

, Fortunaviaza Habib Ainudin

and Muhammad Fikri Fathurrohman

Marine Electrical Engineering, Shipbuilding Institute of Polytechnic Surabaya, Surabaya 60111, Indonesia

Electrical Engineering, Politeknik Elektronika Negeri Surabaya, Surabaya 60111, Indonesia

Department of Electrical Engineering, University of Jember, Jember 68121, Indonesia

Keywords: Controlled Rectifier, Three Phase, DC Shunt Motor, Characteristic.

Abstract: A modern control of electric motor’s speed in an industry needs a variable direct voltage. Mostly, the variable

of the DC motor speeds needs to be control simply by adjusting the voltage variable at the terminal. In

industries, the usage of DC power is limited. Therefore, the support of rectifier in the DC motors is needed to

change AC voltage to DC voltage. Moreover, industries need a concrete rectifier to increase performance of

its DC shunt motor. The variable direct voltage can be supplied by semiconductor devices such as SCR. The

output voltage of a SCR rectifier depends on the delay angle of the SCR. The aim of this research is to make

a SCR rectifier circuit and applying it for observing the characteristics of a shunt direct current motor. The

result shows the circuit can work to demonstrate the shunt motor characteristic. The support of proper rectifier

will be maximizing the performance of DC shunt motor. So that, supported the productivity in each industry.

This rectifier uses a power transformer which acts as a three-phase line voltage ballast. This is because a

rectifier circuit that uses a thyristor (SCR) cannot withstand relatively high unstable voltages. If the voltage

becomes unstable, it may not be possible to properly control the start time of the thyristor. The ignition angle

of the rectifier circuit is regulated by a control circuit which acts as a pulse angle transmitter (α) in the rectifier

power circuit. The testing on this research is using PSIM software to test the performance of rectifier design

before it applied in a prototype. The testing result show relationship between velocity ꞷ

and armature current

Ia, the relationship between torque (T) and armature current (Ia). The result of this research show that the

greater the delay angle of the rectifier, the lower the output voltage of the rectifier which is equal to the motor

input voltage. When the input voltage to the motor decreases, the motor speed m decreases. The effectiveness

of the usage thyristor component in this experiment is supporting the performance of rectifier. The processor

that use in this rectifier, as a form of launch at the gate, uses the TCA 785 chip, which acts as a gate signal

generator for the thyristor, to operate the thyristor and generate a DC waveform at the output terminal.

Therefore, customize design in this research can be used to test the characteristics of a shunt winding DC

motor.

1 INTRODUCTION

DC motor is basically an electric motor with a speed

that can be controlled simply. Speed control for this

type of motor is carried out by adjusting the voltage

at the input terminal (Angga et al). Therefore,

industries that use DC motors as their driving devices

require a DC (variable) voltage source (Applied

Technology and Computing Science Journal 4.1:31-

46., 2021). Most power plants issue AC voltage, so

https://orcid.org/0000-0002-4482-2829

that distribution to consumers is provided with an AC

voltage source (Febrianto., 2021). Therefore, a

voltage rectifier is needed to change the type of AC

voltage to DC (Fitzgerald et al., 1996). The voltage

rectifier used is a controlled rectifier which aims as a

control system to regulate the speed of a DC motor

(Heraja et al, 1984).

Modern control systems need to control DC motor

speed changes, dynamic braking, smooth start and

stop, or reversal of the motor rotation direction (Jacob

Nugraha, A., Eviningsih, R., Intyanto, G., Yuniza, S., Ainudin, F. and Fathurrohman, M.

Three Phase Controlled Rectiﬁer Circuit for Characteristic Control in DC Shunt Motor.

DOI: 10.5220/0011713700003575

In Proceedings of the 5th International Conference on Applied Science and Technology on Engineering Science (iCAST-ES 2022), pages 107-112

ISBN: 978-989-758-619-4; ISSN: 2975-8246

107

M et al, 1990). All this can be done easily and well

with rectifier devices that use semiconductor

components such as diodes, transistors, thyristors

(SCRs), and triacs (Kenjo.,1995). These

semiconductor devices have no moving parts and are

easy to maintain. In addition, these semiconductor

devices are safer to use in hazardous environments,

such as the presence of flammable gases and vapors,

as there is no spark or arc discharge (M Agus

Praztyio., 2016).

The output voltage generated by the thyristor

component (SCR) depends on the firing angle of the

thyristor (Malvino and Barmawi (1996). The phase

control thyristor is turned on by applying a short pulse

to the gate and turned off by natural commutation.

The controlled thyristor rectifier is a simple and

efficient rectifier for controlling motors with

adjustable speed, from small motors to megawatt

motors (Nugraha et al., 2022).

This research was conducted to make a three-

phase semi-controlled rectifier circuit using SCR

(Petruzella., 2001). This three-phase semi-controlled

rectifier has an input voltage of 3 x 110 VAC and a

variable output voltage of 0 - 220 VDC with a current

of 7.5 amperes. Furthermore, this rectifier circuit is

applied to control the shunt direct current motor by

adjusting the rectifier output voltage (Priyambodo et

al., 2021). From setting the output voltage of this

rectifier, the characteristics of the motor can be tested

(Putra et al., 2021).

Through this research there were several problems

were found in this paper, including the arrangement

of controlled rectifier circuit and the working

principle of the rectifier circuit to regulate the

rotational speed of DC motor. So that, by this study it

will fulfilling some purpose there were knowing the

arrangement of the controlled rectifier circuit and the

working principle of rectifier circuit so it can control

the speed of DC motor.

2 LITERATURE RIVIEW

2.1 Three Phase Controlled Rectifier

Motor control with semiconductor equipment using a

three-phase controlled rectifier circuit using SCR is

shown in Figure 1 (Raysid.,(1999).

Figure 1: Controlled Rectifier Circuit Model 3-Phase with

Thyristor.

This rectifier circuit consists of three thyristors

and three diodes. The ignition angle (α) can be

adjusted in steps from 0 to 180°. During the period

from 30° to 210°, thyristor T1 is forward biased.

When T1 is turned on at t = 30° +, T1 and D1 are

connected and the line voltage Vac appears across the

load. At t = 210°, Vac starts negative and the

freewheeling diode Dm is connected. The load

current continues to flow through Dm. T1 and D1 are

off. Without the freewheeling diode Dm, thyristor T2

is turned on at t = 150° + and T1 remains connected

until freewheeling operation is produced by T1 and

D2. At 60°, any thyristor connected to a diode with

120° freewheeling Dm will not be connected (Realdo

et al., 2021).

If the corresponding line to line voltage is defined

as follows:

𝑉



𝑉



𝑉





√

3𝑉∠  30°

(1)

𝑉



𝑉



𝑉





√

3𝑉∠  90°

(2)

𝑉



𝑉



𝑉





√

3𝑉∠  150°

(3)

Or 𝑉





√

3𝑉∠  150°

(4)

The schematic of a shunt winding DC motor is

described. In this motor, the armature circuit and the

shunt field circuit are connected by a DC power

supply with a fixed voltage Vt. The external field

shear resistance (Rtc) is used in the field circuit to

control the motor speed. Since this motor draws

power from the DC power supply, the motor current

flows into the machine from the positive terminal of

the DC power supply. Three-phase controlled

rectifier circuit has components that are connected so

that it can rectify AC voltage into DC voltage. The

components in a three-phase controlled rectifier

circuit, including:

2.1.1 Thyristor

Thyristors are active electronic components that can

be used like doors, namely, to withstand AC current

iCAST-ES 2022 - International Conference on Applied Science and Technology on Engineering Science

108

or pass AC current using a small input source. The

use of thyristors in electronic circuits is generally

used as a switch. Thyristor is a semiconductor

component that is made of silicon. The thyristor has

three legs including the anode, cathode and gate pins.

2.1.2 Transformator Stepdown

A step-down transformer is a transformer that is

useful for lowering the mains voltage, which is the

opposite of a step-up transformer. In an electronic

circuit, this type of step-down transformer is widely

used in power supplies, both regulated and

unregulated power supplies. The function of this type

of transformer in the field of electronics is already

familiar because it is used to replace batteries.

Without a power supply that uses a step-down

transformer, the battery power supply system in

electronic circuits is very inefficient, especially in

terms of cost.

2.2 Direct Current Motor Shunt

The schematic of a shunt winding DC motor is

described by Sen (1987) as shown in Figure 2 in this

motor, the armature circuit and the shunt field circuit

are connected by a DC power supply with a fixed

voltage Vt.

The external field shear resistance (Rtc) is used in

the field circuit to control the motor speed. Since this

motor draws power from the DC power supply, the

motor current flows into the machine from the

positive terminal of the DC power supply.

The motor equation for steady state operation is as

follows:



I



𝐸



(5)



I



I



(6)







𝜙𝜔



(7)

𝐸



𝑉



𝐼



𝑅



(8)

The armature current (I

) and motor speed ꞷ

depend on the mechanical load connected to the

motor shaft.

Figure 2: The equivalent circuit of a shunt direct current

motor (Priyambodo et al., 2021).

3 METHODS

This research will be conducted virtually using PSIM

software. Schematic of the design in Figure 1. The

research was carried out with the initial stages of

preparing tools and components that would later be

used to make a controlled three-phase rectifier circuit.

Making a controlled three-phase rectifier circuit

begins with setting and taking the components that

will be used, then pulling the circuit wiring path on

the schematic board, as shown in Figure 1. After that,

the input voltage amplitude setting on each Variac is

set to 110V. After setting up and making the scheme,

the voltmeter and ammeter were installed which aims

to determine the value of voltage and current on the

source side and the load side.

After the circuit is ready, then a test is carried out

by turning on the power supply. During the trial,

sampling of experimental data will be carried out by

recording the values that appear on the voltmeter and

ampere meter measuring instruments to the

experimental results table. This research was

conducted with two types of experiments, namely

experiments with constant loads and experiments

with varying loads. After the experiment is complete,

the power will be turned off.

4 RESULT OF THE STUDY

The specifications of the rectifier made are as

follows:

𝑉



 0  100𝑉



(9)

𝑉



 3  110𝑉



(10)

𝑉



7,5

𝐴

(11)

Three Phase Controlled Rectiﬁer Circuit for Characteristic Control in DC Shunt Motor

109

4.1 Block Diagram

This rectifier uses a power transformer which acts as

a three-phase line voltage ballast. This is because a

rectifier circuit that uses a thyristor (SCR) cannot

withstand relatively high unstable voltages. If the

voltage becomes unstable, it may not be possible to

properly control the start time of the thyristor.

Figure 3: Block circuit diagram.

The ignition angle of the rectifier circuit is

regulated by a control circuit which acts as a pulse

angle transmitter (α) in the rectifier power circuit. The

step-down transformer used has a rated current of 1

amp and an output voltage of 15 volts and is used as

a power source for the processor IC pins. This IC acts

as a sine wave sync and produces a sawtooth wave.

The processor, as a form of launch at the gate, uses

the TCA 785 chip, which acts as a gate signal

generator for the thyristor, to operate the thyristor and

generate a DC waveform at the output terminal.

Capacitors and filters are used to form a better DC

filter. With filter capacitors, when the voltage rises,

the capacitor is charged, and when the voltage reaches

zero, the capacitor discharges that charge to the load.

Whereas in an inductor filter, the inductor

accumulates current when the current decreases, and

the inductor discards the stored current when the

current rises.

4.2 Control Circuit

The control circuit consists of the following:

1. The TCA 785 chip processor SCR trigger

control circuit uses the TCA 785 chip processor

to control the ignition angle of the rectifier

circuit to create a DC voltage variable.

2. Pulse Transformer Driver Circuit A pulse

transformer is used as a component to form a

trigger pulse which is supplied to the gate of the

SCR. The trigger pulse is generated from the

square wave signal generated by the switching

transistor. Transistor-based controllers, on the

other hand, emit pulses from the TCA 785 chip

processor.

Figure 4: Control circuit of three-phase controlled rectifier.

4.3 Testing

Figure 4 is the implementation used for the circuit and

will be simulated for discussion. The following is a

table containing test result data, including the

following:

4.3.1 Measurement with Constant Load,

Torque (T) = 0.1 N-M

Table 1: Measurement data with constant load.

No Trigger

Angle

(α)°

Rectifier

Output

Voltage

(Volt)

Field

Current

(mA)

Anchor

Current

(A)

Load

Current

(A)

Torque

(N-m)

Speed

Motor

(RPM)

1 50 210 90 0,24 0,45 0 2600

2 55 200 86 0,24 0,575 0,1 2500

3 65 180 76 0,28 0,65 0,1 2250

4 75 160 68 0,3 0,675 0,1 2050

5 85 140 60 0,32 0,7 0,1 1875

6 95 120 50 0,34 0,725 0,1 1700

7 105 100 42 0,325 0,775 0,1 1500

8 115 80 32 0,32 0,95 0,1 1150

From the above experiment, the greater the delay

angle of the rectifier, the lower the output voltage of

the rectifier which is equal to the motor input voltage.

When the input voltage to the motor decreases, the

iCAST-ES 2022 - International Conference on Applied Science and Technology on Engineering Science

110

motor speed m decreases. It can also be seen that the

field current decreases as the input voltage to the

motor decreases, and the load current increases as the

voltage decreases. Figure 5 shows a graph of the

rectifier output voltage and motor speed as a function

of the discharge angle at torque T = 0.1 N–m

(constant).

Figure 5: Graph of rectifier output voltage and motor speed

as a function of trigger angle.

4.3.2 Measurement with Changing Load

Table 2: Measurement data with changing load.

No Trigger

Angle

(α)°

Rectifier

Output

Voltage

(Volt)

Field

Current

(mA)

Anchor

Current

(A)

Load

Current

(A)

Torque

(N-m)

Speed

Motor

(RPM)

1 85 140

58 0,32 0,4 0 2000

57 0,36 1,15 0,3 1675

56 0,42 1,6 0,45 1500

56 0,54 2,4 0,6 1300

2 105 100

40 0,32 0,42 0 1700

39 0,42 1,55 0,3 1050

38 0,48 1,9 0,35 800

38 0,60 2,5 0,45 500

3 115 80

34 0,37 0,5 0 1500

34 0,35 0,8 0,1 1350

32 0,38 1,4 0,2 900

32 0,42 1,8 0,3 400

Figure 6 shows a graph of the rectifier output voltage

and motor speed as a function of the discharge angle

at torque T = 0 N–m.

From the experimental data above, we can see the

characteristics of the motor, including:

Relationship between velocity ꞷ

and armature

current Ia. In this experiment, the magnetic flux is

assumed to be constant, so m is proportional to Ea,

and if the motor rotation is also constant, Ea will be

constant. Ea and magnetic flux decrease with

increasing load. As the load increases, the rotor speed

decreases and the counter electromotive force (Ea)

decreases. The smaller Ea, the greater the ratio of Ea

to Vt (Ea << Vt). Therefore, the armature current (Ia)

drawn from the source by the motor increases.

Lowering Ea affects speed when slowing down. As

the load increases, the speed will decrease.

Figure 6: Graph of rectifier output voltage and motor speed

as a function of trigger angle.

Figure 7: Graph of velocity as a function of armature

current ꞷ

= f(Ia), Vt constant.

Figure 8: Graph of torque as a function of armature current,

T = f(Ia), Vt konstan.

When viewed through the relationship between

torque (T) and armature current (Ia), when the

terminal voltage Vt is constant, the magnetic

amplifier current (Im) is also constant, so it is

210

200

180

160

140

120

100

2600

2500

2250

2050

1875

1700

1500

1150

500

1000

1500

2000

2500

3000

50 55 65 75 85 95 105 115

Voltage (Volt) Revolution per Minute (RPM)

140

100

2000

1700

1500

500

1000

1500

2000

2500

85 105 115

Voltage (Volt) Revolution per Minute (RPM)

2000

1675

1500

1300

500

1000

1500

2000

2500

0,41,151,6 2,4

Revolution per Minute (RPM)

Load Current (A)

0,3

0,45

0,6

0,2

0,4

0,6

0,4 1,15 1,6 2,4

Torque (N-m)

Load Current (A)

Three Phase Controlled Rectiﬁer Circuit for Characteristic Control in DC Shunt Motor

111

constant. When the terminal voltage is constant, the

torque of the shunt winding motor depends only on

the armature current (Ia). From the torque equation

when T = K.Ia.Φ. Therefore, T depends on the

armature current (Ia). In the above experiment, the

greater the torque, the greater the torque. Torque

characteristics as a function of armature current at

140 volts.

5 CONCLUSIONS

After testing the three-phase controlled rectifier

circuit, conclusions can be drawn, including:

1. In general, the effectiveness of using a thyristor

as the main component of a rectifier using phase

control techniques is very good, but this is

actually a refinement of the trigger pulse

generator control circuit to achieve maximum

performance, depending on the degree. In this

tool, the synchronization of the control signal

processing output with the network input signal

is a very important part because the delay in the

input signal sampling time and trigger pulse

generation for control is increased.

2. In a constant load test, the maximum output

voltage occurs at a trigger angle = 50°, or 210

volts at a motor speed of 2600 rpm. When the

output voltage of the rectifier drops to 80 volts,

the motor speed also drops significantly to 1150

rpm. In this experiment, it was found that as the

delay angle of the rectifier increases, the input

voltage of the motor decreases. When the input

voltage drops, the motor speed m drops.

3. From testing with different loads, at a constant

motor terminal voltage, the motor speed

decreases with increasing load (the torque value

increases). Example: If the motor input voltage

is 140 volts, the motor speed is 2000 rpm and

the torque is 0. Increasing the torque to 0.3 N –

m will decrease the motor speed to 1675 rpm. If

the torque is increased to 0.45Nm, the engine

speed will drop to 1500rpm. Then, when the

torque increases to 0.6 Nm, the engine speed

drops more significantly to 1300 rpm.

4. Adjusting the angle on the thyristor used in this

rectifier can affect the output voltage for the

motor, thus causing a decrease or increase in

RPM. So this controlled rectifier is very suitable

for use when requiring changes in RPM speed

without changing the input voltage value.

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