Blocked rotor test

A blocked rotor test is conducted on an induction motor. It is also known as short-circuit test (because it is the mechanical analogy of a transformer short-circuit test),[1] locked rotor test or stalled torque test.[2] From this test, short-circuit current at normal voltage, power factor on short circuit, total leakage reactance, and starting torque of the motor can be found. It is very important to know a motor's starting torque since if it is not enough to overcome the initial friction of its intended load then it will remain stationary while drawing an excessive current and rapidly overheat.[3] The test may be conducted at lower voltage because at the normal voltage the current through the windings would be high enough to rapidly overheat and damage them. The test may still be conducted at full voltage if it is brief enough to avoid overheating the windings or overloading the starting circuits, but requires much more care to be taken while performing the test.[4] The blocked rotor torque test is less significant on wound-rotor motors because the starting torque of these wound-rotor motors depend upon the external resistance added. However, it may still be used to characterise the motor.[3]

  1. ^ U.A.Bakshi, M.V.Bakshi, Electrical Machines - II, p. 6-7, Technical Publications, 2009 ISBN 8184315236.
  2. ^ M.V. Deshpande, Electrical Machines, p. 254, PHI Learning, 2011 ISBN 8120340264.
  3. ^ a b Industrial Power Engineering and Applications Handbook. Newnes. 8 October 2001. ISBN 9780080508634.
  4. ^ "Motor testing methods". Electronic Systems of Wisconsin, Inc. Archived from the original on 2012-12-31.