⚡ Q·Bank BWSSB AE

• Current transformers are __________________
  series connected type of instrument transformers
• Why is the transformer core laminated?
  To reduce eddy current losses. Laminations are thin sheets of steel insulated from each other by varnish. This increases the resistance to circulating eddy currents, minimizing heat and energy loss.
• Which parameters are determined by the Open Circuit (OC) and Short Circuit (SC) tests on a transformer?
  OC Test: Core loss (Iron loss), Magnetizing reactance (Xm), and Core loss resistance (Rc). Performed on LV side with HV open.
  
  SC Test: Copper loss at full load, Equivalent resistance (Req), and Equivalent leakage reactance (Xeq). Performed on HV side with LV shorted.
• Which parameters are determined by the Open Circuit (OC) and Short Circuit (SC) tests on a transformer?
  OC Test: Core loss (Iron loss), Magnetizing reactance (Xm), and Core loss resistance (Rc). Performed on LV side with HV open.
  
  SC Test: Copper loss at full load, Equivalent resistance (Req), and Equivalent leakage reactance (Xeq). Performed on HV side with LV shorted.
• Which of the following is not a part of transformer installation?
  Exciter
  
  
• Transformer core is generally made of ___________
  By stacking large number of sheets together
  
  
• The purpose of the transformer core is to provide ____________
  Low reluctance path
  
  
• What is the thickness of laminations used in a transformer?
  0.1 mm to 0.5 mm
  
  
• Power transformers other than distribution transformers are generally designed to have maximum efficiency around ______
  Near full-load
  
  
• No-load current in the transformer is ____
  Sinusoidal distorted
  
  
• Core flux in the transformer is _______________
  flat-topped
  
  
• What is the dielectric strength of a transformer oil?
  35 kV
  
  
• The insulating material that can withstand the highest temperature safely is _______________
  Mica
  
  
• For the parallel operation of two single phase transformers it is necessary that they should have ________
  same polarity
  
  
• Transformers operating in parallel mode of operation will share the load depending upon their ___________
  per unit impedance
  
  
• What will happen if the transformers working in parallel are not connected with regard to polarity?
  Incorrect polarity will result in dead short circuit
  
  
• Why transformers connected in parallel should have same voltage ratio?
  To avoid no-load circulating current