Question 1
A step-down transformer has more turns on the primary than on the secondary winding. How does this affect voltage and current on the secondary (ignoring losses)?
Question 2
A transformer has a primary of 240 V and a secondary of 24 V. If the primary has 400 turns, approximately how many turns are on the secondary?
Question 3
Why might an isolation transformer be installed to feed sensitive electronic equipment?
Question 4
Which type of transformer connection is capable of providing a neutral point in a 3-phase system?
Question 5
When paralleling two single-phase transformers, which condition is essential to prevent a short circuit?
Question 6
A 3-phase Delta transformer bank has one transformer fail. The remaining two are reconnected in Open-Delta. What is the new capacity relative to the original bank?
Question 7
If a transformer is humming excessively, what is a likely cause?
Question 8
A 45 kVA transformer bank is connected in a Delta-Delta configuration. If one transformer is removed to operate in Open-Delta, what is the new total kVA capacity?
Question 9
When wiring a transformer in parallel, which property must match exactly to avoid short circuits?
Question 10
If a transformer hums excessively, what is the likely cause?
Question 11
In a transformer, which of the following remains constant between the primary and secondary sides, assuming an ideal transformer with no losses?
Question 12
In a Step-Down transformer with a primary voltage of 600V and a secondary voltage of 120V, what is the 'turns ratio' (primary to secondary)?
Question 13
In a 600V to 120/208V step-down transformer, which side is the secondary?
Question 14
In a 3-phase, 4-wire, 120/208V system, what is the theoretical voltage between any phase conductor and the neutral conductor?
Question 15
A feeder from a 600 V switchboard supplies a 600/120-240 V transformer. The secondary neutral must be grounded. Where is the MOST appropriate location to bond the neutral to the grounding electrode system?
Question 16
On a single-line diagram, a transformer is usually represented by which type of symbol?
Question 17
In a low-voltage doorbell circuit using a transformer, which side of the transformer connects to the 120 V supply?
Question 18
A three-phase, 208 V panelboard feeds a 10 kVA, 120 V/208 V dry-type transformer for a receptacle panel. If the transformer primary current is approximately 28 A, which is the best way to coordinate the primary overcurrent device?
Question 19
In a transformer, if the primary voltage is 480V and the secondary voltage is 120V, what is the turns ratio?
Question 20
What is the primary benefit of a 'zig-zag' grounding transformer?
Question 21
Which transformer connection is capable of providing both 3-phase 480V and 277V lighting loads?
Question 22
Which type of transformer connection creates a 'High-Leg' or 'Stinger' leg?
Question 23
What is the voltage to ground of the 'High Leg' in a 120/240V Delta 4-wire system?
Question 24
What is a 'K-rated' transformer designed to handle?
Question 25
A step-down transformer has a primary voltage of 480V and a secondary voltage of 120V. If the turns ratio is 4:1, what is the secondary current if the primary draws 2A (assume ideal)?
Question 26
Three-phase power is supplied to a building. You measure 208V between Phase A and Phase B, 208V between B and C, and 208V between C and A. You measure 120V between any phase and Neutral. What type of system is this?
Question 27
When wiring a transformer, the 'X' terminals typically designate the:
Question 28
In a transformer, if the primary voltage is 480V and the secondary is 120V, this is a ______ transformer.