ELECTRICAL ENGINEERING LABORATORY 2

(EEE 240)

EXPERIMENT 1

DC MACHINE

OBJECTIVES

1. To construct the circuit for recording the speed-voltage characteristic of a

separately excited direct-current (DC) motor according to the diagram.

2. To record the speed as a function to the armature voltage of a seperately

excited DC motor, to represent it graphically and to describe it.

3. To connect and start a saparately excited motor for the recording of the

characteristic of a speed and torque for different armature voltage according

to the currentdiagram.

4. To record the characteristic of speed and torque for a separately excited DC

motor and represent it graphically in order to describe the characteristic of

speed and torque.

LIST OF APPARATUS

Equipment

1. Voltage supply (2 units)

2. Voltmeter

3. Ammeter

4. Separately excited DC motor

5. Control unit

6. Display panel

7. Brake

8. Shaft and cover (2 units)

9. Coupling collar

10.Coupling cover

11.Connection mask (code: 3125111)

12.Connection mask (code: 3125101)

THEORY

DC MOTOR

The DC motor has two basic parts: the rotating part that is called the armature and the stationary part that includes coils of wire called the field coils. The stationary part is also called the stator. Figure 12-1 shows a picture of a typical DC motor, Fig. 12-2 shows a picture of a DC armature, and Fig. 12-3 shows a picture of a typical stator. From the picture in Fig. 12-2 you can see the armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates on bearings. You should also notice that the ends of each coil of wire on the armature are terminated at one end of the armature. The termination points are called the commutator and this is where the brushes make electrical contact to bring electrical current from the stationary part to the rotating part of the machine.

The picture in Fig. 12-3 shows the location of the coils that are mounted inside the stator. These coils will be referred to as field coils in future discussions and they may be connected in series or parallel with each other to create changes of torque in the motor. You will find the size of wire in these coils and the number of turns of wire in the coil will depend on the effect that is trying to be achieved.

Figure 1.1: A typical DC motor.

Figure 1.2: The armature (rotor) of a DC motor has coils of wire wrapped around its core. The ends of each coil are terminated at commutator segments

located on the left end of the shaft. The brushes make contact on the commutator to provide current for the armature.

Figure 1.3: The stationary part of a DC motor has the field coils mounted in It.

1. The equivalent circuit of a separately excited DC is shown in Figure 1.1.

2. The power flow diagram of a shunt DC motor is as shown in Figure 1.2.

PROCEDURES

PART A: SEPERATELY EXCITED DC MOTOR, SPEED AND VOLTAGE

CHARACTERISTIC, N= f (v)

1. The connections was set according to the current diagram shown in Figure 1.3.

2. Before starting the motor, the operating elements of the control unit was

adjusted as shown in Table 1.1.

3. The motor was started. An armature voltage value adjusted to 220V (the rated

voltage of the motor).

4. The direction of the motor was checked. By using the display. The motor turn

clockwise. The control unit was adjusted to torque value of 1.0 Nm.

5. The speed measured. The measured value was recorded in Table 1.2(a). the

experiment was repeated with different armature voltage values as shown in

Table 1.2(a).

6. Step 1 to 4 was repeated for the torque of 2.0 Nm and was recorded in Table

1.2(b).

7. The speed was plotted as a function of the armature voltage, N= ƒ (V) in Graph

1.2(a) and 1.2(b).

PART B: SEPERATELY EXCITED DC MOTOR, SPEED AND TORQUE

CHARACTERISTIC AT DIFFERENT ARMATURE VOLTAGE, N=ƒ(r)

1. The connections were set up according to the current diagram shown in Figure

1.5.

2. The operating elements of the control unit were adjusted before starting the

circuit as shown in Table 1.3.

3. The motor was started. The rated load excitation current was adjusted and the

armature voltage was kept to be constant at 50V. the direction of the motor was

checked by using the display. It turned clockwise. The speed measured at no

load ( = 0 Nm) and at other torque values. The measured value recorded in

Table 1.4.

4. The experiment was repeated with different armature voltages and torque value

as shown in Table 1.4. The speed was recorded.

5. The speed was plotted as a function of torque with N = ƒ (Ʈ) for different

armature voltages graphically in Graph 1.4.

RESULT

PART A

Voltage 220 200 180 160 140 120 100 80 60 40 20 0

Speed 2835 2510 2240 2010 1705 1445 1198 888 590 320 72 0

Current Armature(Ia)

1.9 1.9 1.8 1,8 1.7 1.6 1.6 1.5 1.5 1.4 1.3 0

Current Field

(If)

0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

Table 1.2(a) when applying torque 1.0

Voltage 220 200 180 160 140 120 100 80 60 40 20 0

Speed 2540 2380 2120 1890 1570 1320 1055 760 495 215 0 0

Current Armature(Ia)

3 3 3 3 3 2.9 2.9 2.9 2.9 2.8 2.1 0

Current Field

(If)

0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

Table 1.2(b) when applying torque 2.0

Part B

Voltage

50 Volt 100 Volt 150 Volt 200 Volt 220 Volt

Torque

Speed

Current Armature

(Ia)

Speed

Current Armature

(Ia)

Speed

Current Armature

(Ia)

Speed

Current Armature

(Ia)

Speed

Current Armature

(Ia)

0 680 0.2 1280 0.5 1970 0.6 2585 0.7 2900 0.7

0.2 645 0.6 1250 0.7 1956 0,7 2567 0.8 2888 0.8

0.4 612 0.8 1225 0.9 1915 1.0 2533 1.1 2867 1.1

0.6 580 1.1 1200 1.1 1897 1.2 2511 1.3 2840 1.3

0.8 545 1.3 1170 1.3 1866 1.4 2490 1.5 2800 1.8

1.0 524 1.4 1140 1.5 1833 1.7 2460 1.8 2750 1.9

REFERENCES

D.F. Warne,(2000). Newnes Electrical Engineer’s Handbook, Newnes.

Rusnani Ariffin and Mohd Aminudin Murad, (2010).Laboratory Manual Electrical

Engineering Laboratory 2 EEE 240.University Publication Centre (UPENA).

Steven M. Kaplan, (2007). Wiley Electrical and Electronics engineering dictionary.

Wiley-interscience. John Wiley & Sons,INC.

Paul E. Tippens, (2007). Physics (7 th Ed.).McGraw Hill International Edition.

http://www.gallantmotor.com/acvsdc retrieved on 18 march 2013

TABLE OF CONTENT

Topic Page

Introduction

Objectives and Equipments

Procedure

Result

Discussion

Conclusion

Reference