Apprentice Lineman Transformer
Theory Test Questions With Complete
Answers
\.Why is a Closed Wye - Closed Delta primary neutral floated? - Answer- To prevent the
backfeed of full primary voltage if a line cutout is blown.
\.Why is a 4th cutout installed on the primary neutral of a closed Wye -closed Delta Bank? -
Answer- To prevent Ferroresonance while switching.
\.On an open transformer bank, what KVA capacity is the bank rated for? - Answer- 86.6% of
nameplate ratings.
\.Expain the term "Backfeed" - Answer- Feeding the primary coil through the secondary coil.
\.What must be done before climbing above a transformer? - Answer- Make sure the tank
ground is intact, de-energize the high side and remove secondary leads.
\.What determines the amount of voltage drop when a transformer is fully loaded? - Answer-
Impedance
\.Explain polarity of a transformer. - Answer- Relative direction of current flow primary to
secondary.
, \.When paralleling or banking transformers, the impedance must be within _____% of each
other? - Answer- 10%
\.What KVA capacity would you have if you convert a closed delta bank to an open delta bank? -
Answer- 57.7% of the original 3 transformers. OR 86.6 of the remaining 2.
\.How much capacity would you gain from using a closed delta bank instead of an open delta
bank? - Answer- (57.7 to 100%) = 42.3%
\.What do you need to do with the neutral connection on a closed wye -closed wye transformer
bank? - Answer- Tie the primary neutral.
\.What purpose does the case ground serve on a transformer? - Answer- To make sure the
transformer case doesn't become energized, and on a single bushing transformer the case
ground is the H2 connection.
\.Name the types of transformer banks you can make with two or three transformers. - Answer-
Wye-Wye, Wye-Delta, Delta-Delta, Delta-Wye, Open Wye-Delta, Open Delta-Delta
\.What does CSP mean? - Answer- Completely self protected
\.On a CSP transformer, what coil is the circuit breaker on? - Answer- Secondary
\.Taps are used for two purposes, name them. - Answer- Control voltage to the customer and
correct low primary voltage *raise the tap to lower the secondary voltage*
\.T or F, Two cutouts and arrestors are needed on a wye connected transformer. - Answer-
FALSE
Theory Test Questions With Complete
Answers
\.Why is a Closed Wye - Closed Delta primary neutral floated? - Answer- To prevent the
backfeed of full primary voltage if a line cutout is blown.
\.Why is a 4th cutout installed on the primary neutral of a closed Wye -closed Delta Bank? -
Answer- To prevent Ferroresonance while switching.
\.On an open transformer bank, what KVA capacity is the bank rated for? - Answer- 86.6% of
nameplate ratings.
\.Expain the term "Backfeed" - Answer- Feeding the primary coil through the secondary coil.
\.What must be done before climbing above a transformer? - Answer- Make sure the tank
ground is intact, de-energize the high side and remove secondary leads.
\.What determines the amount of voltage drop when a transformer is fully loaded? - Answer-
Impedance
\.Explain polarity of a transformer. - Answer- Relative direction of current flow primary to
secondary.
, \.When paralleling or banking transformers, the impedance must be within _____% of each
other? - Answer- 10%
\.What KVA capacity would you have if you convert a closed delta bank to an open delta bank? -
Answer- 57.7% of the original 3 transformers. OR 86.6 of the remaining 2.
\.How much capacity would you gain from using a closed delta bank instead of an open delta
bank? - Answer- (57.7 to 100%) = 42.3%
\.What do you need to do with the neutral connection on a closed wye -closed wye transformer
bank? - Answer- Tie the primary neutral.
\.What purpose does the case ground serve on a transformer? - Answer- To make sure the
transformer case doesn't become energized, and on a single bushing transformer the case
ground is the H2 connection.
\.Name the types of transformer banks you can make with two or three transformers. - Answer-
Wye-Wye, Wye-Delta, Delta-Delta, Delta-Wye, Open Wye-Delta, Open Delta-Delta
\.What does CSP mean? - Answer- Completely self protected
\.On a CSP transformer, what coil is the circuit breaker on? - Answer- Secondary
\.Taps are used for two purposes, name them. - Answer- Control voltage to the customer and
correct low primary voltage *raise the tap to lower the secondary voltage*
\.T or F, Two cutouts and arrestors are needed on a wye connected transformer. - Answer-
FALSE
