Transformer Theory
The amperage of a single phase transformer is found by dividing the KVA rating of transformer by the primary or ___ voltage.
What is secondary voltage?
The formula that is used for single phase transformers Short-Circuit Fault current.
What is FLA/IMPEDANCE?
FLA/Z?
The table used for calculating the OCPD device for a transformer rated over 1000 volts.
What is TABLE 450.3 (A)?
This is the NEC Article that covers "Over-current Protection".
What is Article 240?
Defined as an area including a basin with a toilet and/or shower.
What is bathroom? Article 100 definitions
The windings of a open-delta connected system only pull what percentage of the line current.
What is 58%?
The square root of 3.
What is 1.732?
What NEC article would be used to determine the next larger standard size OCPD?
What is SECTION 240.6 (A)?
This type of fuse is used when a high in-rush current is expected at start-up.
What is a "dual-element time-delay fuse?
How many #12THHN conductors can you legally install in a 3/4" EMT conduit?
What is 16? Annex C Table C.12
Chap 9 Table 5 #12 0.0133
Chap 9 Table 4 3/4" 40% 0.213
0.213/0.0133 = 16.02
Voltage reading phase to phase on a 277/480 volt wye system.
What is 480 volts?
The number you get if you divided 480 by 277.
What is 1.732?
The NEC article that covers Motor installations.
What is Article 430?
Using table 450.3 (B) what would the maximum OCPD need to be set at for a 480 volt 3 phase transformer rated at 30 KVA. Providing primary only protection?
What is A 50 AMP OCPD?
30000/(480 x 1.73) = 36.13
36.13 x 125% = 45.15 240.6(A) allows 50 amp
The rated ampacity of a 4/0 AWG, XHHW-2 copper conductor.
What is 260 amps?
Table 310.16
This transformer configuration produces these secondary voltages phase to ground, 120, 120, 208.
What is a "Delta"?
The ratio of a 7200 volts to 240 volts.
What is 30:1?
This NEC Article covers working space around equipment.
What is Article 110?
The maximum number of disconnects that can be grouped together without requiring a "Main" disconnect.
What is 6? 230.71(A)(B)
The article that covers the installations of Hydromassage tubs.
What is ARTICLE 680? Part VII of 680
If the transformer voltage is increased the current will do this.
What is DECREASE?
Assuming a pf of 1.0, a single phase 10kVA transformer will produce a load of _____amps @ 240V.
What is 42 Amps? 41.667 Amps
This NEC Article covers "Capacitors".
What is NEC Article 460?
OCPD shall be provided in each ungrounded circuit conductor and shall be located here.
What is at the point where conductors receive their supply? 240.21
This Article covers the installations of Generators.
What is ARTICLE 445?