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Dc Motor Characteristic.

By:   •  March 22, 2019  •  Term Paper  •  621 Words (3 Pages)  •  173 Views

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UON Newcastle

Lab Report  (5 ) ELEC2132                                                                                                                              20.11.2016

DC MOTOR CHARACTERISTIC

Conducted By :

As shown in the diagram 5 the circuit is connected with the exception that the motor is connected to +5v terminal via the ammeter. 5V dc supply is connected to the trainer and the ammeter is observed as speed of the motor increases. The initial current is measured. In less than a second, the current is read when the speed is stabilized. This exercise for 15V is repeated and the results are checked. They are recorded in the following table.

Voltage

Initial Current (mA)

Stabilised Current (mA)

5

3.6

3.07

15

9.7

4.6

[pic 1][pic 2]

6 At heavy load , armature current Ia  is large and hence ,speed is low which result in decreased back Emf eb . due to decreased Eb, more armature current is allowed . . At this point, the armature current stops decreasing and remains constant.

 The circuit is connected up as shown in the patching diagram of Figure 6. Variable resistor

RV1 is turned fully counterclockwise(min). 15V dc, 0.3A supply is connected.

RV1 is turned clockwise and the ammeter connected in the generator output circuit is read. The generator output voltage and the armature current is observed. They are recorded in the following table.

Load Current (mA)

Generator Voltage (v)

Load resistance (ohms)

Armature Current (mA)

0.018

1.17

0.065

0.43

0.035

1.1

0.0314

0.44

0.061

1.07

0.0175

0.45

0.099

0.992

0.01

0.49

0.145

0.828

0.0057

0.529

[pic 3]

7.As the armature current increases , load resistance decrease and load current increases The generator voltages decreased with increasing load current because of the voltage drop across the load resistance (E=IR).

8. Exercise 6: DC Generator

Aim: To investigate the operation of a dc generator

The circuit is connected up as shown in the patching diagram of Fig7. The power supply is set to 10V output and the output voltage is observed on the oscilloscope. The output voltage is recorded in the following table. This exercise is repeated for 6V, 8V and 12V.

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