Question

Electromagnetic Material Practical

Answer 1

Practical Significance

To increase the efficiency of electrical machines and devices like transformer it is necessary to decrease the losses. It is necessary to minimize the core loss; hence the selection of core material is very important.

Competency and Practical Skills

This practical is expected to develop the following skills for the industry identified competency: ‘Plan wiring/cabling activities using relevant materials following safe practices’

i. Construct simple electromagnet

ii. Measure iron losses of various electromagnetic materials.

Practical Outcome

1. Use the coil over core arrangement to determine the iron losses per unit weight of first electromagnetic specimen.

2. Use the coil over core arrangement to determine the iron losses per unit weight of second electromagnetic specimen.

Relevant Affective domain related Outcome(s)

i. Practice good housekeeping with safety measures.

ii. Demonstrate working as a leader/a team member.

iii. Maintain tools and equipment.

iv. Follow ethical practices.

Minimum Theoretical Background

The hysteresis and eddy current losses occur within the core (magnetic material) of machine or devices. For a given magnetic circuit with a core of ferromagnetic material, volume and thickness of the plates are constant and the total core loss can be expressed as follows.

Core loss = Hysteresis loss + Eddy current loss

The core loss of electromagnetic material can be measure with the help of a wattmeter (W) by energizing the N turn coil having negligible resistance from a sinusoidal voltage of known frequency, keeping constant cross sectional area of the core as shown in fig. 1.

Practical set-up / Circuit diagram / Work Situation

Resources Required

Precautions to be Followed

1 The winding used to construct the setup should be well insulated from core.

2 Insulation paper (used for motor rewinding) may preferably use on the core

3 There should not be any loose connections.

4 Select proper range of meters.

Procedure

1. Take old choke of a florescent lamp (Tube Light) or a small transformer.

2. Dismantle the choke / transformer

3. Remove its windings & use its core to form coil over core arrangement.

4. Measure weight of the core.

5. Select a copper wire of suitable gauge & length (So as to have sufficient number of turns).

6. Measure resistance of the winding using multi—meter.

7. Wind copper wire over the selected core.

8. Connect circuit as shown in circuit diagram Fig. 1.

9. Switch “ON” the supply.

10. Apply suitable voltage across the coil over core with help of autotransformer.

11. Note down the readings of all meters in observation Table.

12. Switch “OFF” supply.

13. Repeat the experiment for various electromagnetic cores of same cross sectional area and size.

14. Compare the results of various core material.