This document outlines a session on transformer design that covers modes of heat dissipation, heating and cooling curves, and calculations of heating and cooling time constants. The session will review the previous material, discuss learning outcomes, and present content on insulation classes, construction of transformers, and heating and cooling curves. Students will be evaluated with questions and asked to prepare for the next session, which will wrap up with a review of the key topics covered.

1. Unit 1: Transformer Design: Part 1
Session-1/36
Modes of heat dissipation. Heating and cooling curves. Calculations of
heating and cooling time constants.
Dr. Anand.V.Satpute
(Associate Professor)
Electrical Engineering Department,
MMCOE, Pune

2. Outline:
A. Attendance
B. Review of the previous session
C. Learning Outcomes of the session
D. Content
E. Student’s evaluation
F. Preparation for next session
G. Wrap up

3. B. Review of previous session:
• Basics of Machines
• Working and Construction of Transformer and IM
• CO-PO attainment of CADEM

4. C. Learning Outcomes of the session:
• Heating and Cooling time constant of Transformer
• Modes of Heat dissipation

5. D. Content:
Content Learning /
Methodology
Faculty
Approach
Typical Student
Activity
Skill/
Competency
Developed
Basics of transmission line PPT, Experimentation
Explain Understand
Critical Thinking -
Observation
Classification of Transmission lines
PPT Explains, Guides Remember
Critical Thinking –
Observation
Performance analysis of Single
phase short transmission lines Chalk Board, PPT,
Demonstration
Explain Listen
Critical Thinking –
Observation
Performance analysis of three
phase short transmission lines Chalk Board, PPT Explain Listen
Critical Thinking –
Inference

6. Modes of heat transfer/ Dissipation

7. Insulation Class

8. Construction and Cut Section of
Transformer

9. Construction and Cut Section of
Transformer

10. HEATING AND COOLING CURVES
A machine can be considered as a homogeneous body developing heat internally at uniform
rate and dissipating heat proportionately to its temperature rise.
Let,

11. HEATING AND COOLING CURVES
Assume that a machine attains a temperature rise after the lapse of
time t seconds.
In an element of time “dt” a small temperature rise “d” takes
place.
Then,
Heat developed = p.dt
Heat developed = Gh.dq
Heat dissipated = Sql. dt
Therefore, total heat developed=heat stored + heat dissipated

12. HEATING AND COOLING CURVES

13. Heating time constant
Heating time constant is defined as the time taken by the machine to attain 0.623 of its final steady temperature rise.
HEATING AND COOLING CURVES

14. If motor where disconnected from supply during cooling, there would be no losses taking place and hence, final temperature reached
will be the ambient temperature.
Cooling time constant
Cooling time constant is, therefore, defined as the time required cooling the machine down to 0.368 times the initial temperature rise
above ambient temperature.
HEATING AND COOLING CURVES

15. E. Student’s evaluation
Questions
List Insulation class classification
Classify Material heat dissipation factor

16. • Methods of cooling of transformer
F. Preparation for Next Session:-

17. G. Wrap Up
In this lecture we have learned
∙ Basics of heat dissipation
∙ Insulation class
∙ Heat dissipation of diff. material
∙ Heating and Cooling curves