QUESTION 2 (a) List any four (4) advantages of an auto-transformer compared with
ID: 2291249 • Letter: Q
Question
QUESTION 2 (a) List any four (4) advantages of an auto-transformer compared with a conventional two-winding transformer (4.0 marks) b) A 120/480-V, 10-KVA two-winding transformer is to be used as an auto-transformer to supply a 480-V circuit from a 600-V source. When it was tested as a two-winding transformer at rated load and unity power factor, its efficiency was 0.979 11) Draw a diagram of the connections as an auto-transformer. Show, clearly, how you derived the auto-transformer from the two- wioding transformer (2) Determine its kVA rating as an auto-transformer (3) Determine its efficiency as an auto-transformer at ful-load, with a 0 85 lagging power-factor. (9.0 marks) (1.0 mark) 5.0 marks)Explanation / Answer
a)
Advantages:
Auto transformer uses single winding so its lesser is size, lesser in cost due to less copper in winding.
In autotransformers part of the power is transferred to the secondary though conduction, which makes it to require less magnetic core and less copper.
Unfortunately autotransformers can’t be used in circuitry where galvanic isolation is a requirement.
Can be used to step up/down the voltage for small amount where needed like from 110 to 120 or 13.2 kV to 13.8 kV.
Apparent power increases since the leakage flux is reduced.
Reduces the budget since you need not to have a separate transformer to step up/down the voltage for this small amount.
Auto transformer uses single winding so its lesser is size, lesser in cost due to less copper in winding. ... Due to single winding it doesn't allow isolation from primary to secondary.