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Electronics Engineering QUESTION #11741
Question 1
A thermal imaging camera shows a hot spot on a three-phase bus bar connection at phase B. All three phases carry equal load current. The most probable cause is:
  • Phase B overloaded compared to A and C
  • Loose or corroded connection causing increased contact resistance✔️
  • Ambient temperature variation across the switchboard
  • Phase B is closer to the heat source of the incoming transformer
Correct Answer Explanation
Under equal current loading, a hot spot on one phase bus connection is almost always caused by a high-resistance joint — loose bolts, corrosion, oxidation, or insufficient contact area. Power dissipated: $P = I^2 R_{contact}$. Even a small increase in contact resistance at high current causes significant heating. The fix is to re-torque, clean, and re-terminate the connection.