Electrical Machines Questions and Answers_pag350

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12. A coupling magnetic field inside a rotating machine or static machine like transformers must 
involve with 
I. electrical system to extract energy from electrical system. 
II. mechanical system to extract energy from electrical system. 
a) Only I is true 
b) Only II is true 
c) I and II are true 
d) I and II are false 
View Answer 
Answer: b 
Explanation: The energy conversion which involves both electrical as well as mechanical 
systems must have mutual field. 
13. I. Pulse transformers use soft ferrites. 
II. The transformers used in the radio recievers use air core. 
a) Only I is true 
b) Only II is true 
c) I and II are true 
d) I and II are false 
View Answer 
Answer: c 
Explanation: Pulse transformers are used in isolation transformer and need high permeablity. 
14. Stepping of the core is implemented in the core to 
a) reduce conductor material and copper losses 
b) reduce core loss 
c) to provide mechanical strength 
d) to reduce magnetizing current 
View Answer 
Answer: a 
Explanation: Stepping of the core is done so that the copper material reduces. 
15. Core type transformers have, LV and HV windings are arranged such that 
a) Half LV near the core and half HV outside LV on each limb 
b) LV one one limb and HV on the other 
c) Half LV outside the core and half HV inside LV on each limb 
d) LV and HV windings are sandwiched 
View Answer 
Answer: a 
Explanation: Core windng has first of all both the windings on the same limb and HV is placed 
outside to have tappings to the transformer. 
16. The shell type transformers have, LV and HV windings are arranged such that 
a) Half LV near the core and half HV outside LV on each limb 
b) LV one one limb and HV on the other 
c) Half LV outside the core and half HV inside LV on each limb 
d) LV and HV windings are sandwiched