The document, presented by Dr. R. Raja, discusses the heating and cooling curves of electrical drives, depicting heat development and dissipation in machines. It defines heating and cooling time constants, illustrating how a machine reaches a steady temperature rise over time. The content is part of a lecture from Muthayammal Engineering College's Department of Electrical and Electronics Engineering.

1. Presented by
Dr. R. RAJA, M.E., Ph.D.,
Associate Professor, Department of EEE,
Muthayammal Engineering College, (Autonomous)
Namakkal (Dt), Rasipuram – 637408
MUTHAYAMMAL ENGINEERING COLLEGE
(An Autonomous Institution)
(Approved by AICTE, New Delhi, Accredited by NAAC, NBA & Affiliated to Anna University),
Rasipuram - 637 408, Namakkal Dist., Tamil Nadu, India.
Electrical Drives and Control
Heating and Cooling Curves

2. 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,
Relation Ship Between Temperature Rise and Time:
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3.  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
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6. 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.
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Cooling time constant
Contd..

9. Thank You
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