Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 2, 3 and 4
 1 and 3
 1, 2 and 4
 1, 2, and 3

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Electrical Machines
In a transformer

 OC test is conducted on LV side and SC test is conducted on HV side
 OC test is conducted on HV side and SC test is conducted on LV side
 both OC and SC tests are conducted on LV side
 both Oc and SC tests are conducted on HV side

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