Grounding and Bonding
Name of the ground wire included in the primary conduit of Transformer T3 in our shop, whose ungrounded conductors are protected by an OCPD
Equipment Grounding Conductor
Proper name for the steel in the ceiling above Transformer T3 where the ground wire lands
Grounding Electrode
Transformer T3 in our shop is a delta/wye transformer with a primary voltage of 480 v and a secondary voltage of 120/208 volts. What is the turns ratio of this transformer and is it a step up or step-down transformer
4:1 Step-Down
The proper name according to the NEC for Transformer T3 is a
Separately Derived System
What are the two types of Overcurrents
Short circuit and Overload
The conductor ran in conduit above Transformer T3, used to provide a connection to the grounding electrode and system bonding point in Transformer T3 in our workshop
Grounding Electrode Conductor
If the ungrounded conductors in the primary conduit feeding Transformer T3 are 3/0. What size Cu does the Grounding Electrode Conductor need to be?
#4 Cu Table 250.66
The primary ungrounded conductors of Transformer T3 land on which terminals
H1, H2, and H3
If I determine that Transformer T3 is not providing the proper output voltage of 120/208. What can I do in the transformer to change the output voltage
Change the coil taps on the high voltage primary
What are the 3 main items that must be marked on molded case circuit breakers
Voltage, Amperage, Interrupting Rating
Name of the conductor that provides the connection between Xo and the system bonding point in Transformer T3 in our shop
System Bonding Jumper
If the ungrounded conductors feeding Transformer T3 are 3/0 and the OCPD protecting those conductors is 100A. What size wire type Cu ground is needed
#8 Cu Table 250.122
X1, X2, and X3
Transformer T3 has primary and secondary protection as required in the NEC. The primary current is 90.2 amps and is protected by a 3 phase 100 amp breaker.
Is this adequate protection based on Article 450 of the code and what is maximum allowable OCPD
Yes, TBL 450.3(B) 2.5 *90.2=225.5 amps, TBL 240.6(A)- 225 amp Maximum OCPD
The primary feeder for Transformer T3 is protected by a 100 amp 3 phase molded case circuit breaker with a 277/480 voltage rating and 18ka interrupting rating.
If the available fault current is 3800 amps at this panel is this properly protected
Yes because 3800 a is less than 18000 amps
The name for the ground ran with the secondary conductors of Transformer T3 in our shop that provides electrical continuity between T3 and the panelboard. It does not have overcurrent protection at its source
Supply Side Bonding Jumper
What size wire type Cu Supply Side Bonding Jumper should be included in the secondary feed from Transformer T3 if the ungrounded conductors are 300 MCM
#2 Cu, Tbl 250.102(C)(1)
Terminal X0 is also known as what since the potential difference between the secondary coils 0 volts is here
neutral point
Transformer T3 requires primary and secondary protection. The secondary conductors are protected by a 225 amp breaker. The secondary rated current is 208.2 amps. Is this adequate protection and what is the maximum size OCPD according to Art 450
TBL 450.3(B)- 1.25 * 208.2= 260.25 amps
Note 1 round up, TBL 240.6(A)- 300 amps
yes
The conductors between the final overcurrent device protecting the circuit and the outlet(s)
Branch Circuit
The white conductor included with the secondary conductors is called a neutral or properly known as a
Grounded Conductor
If a receptacle is fed from circuit #2 of our 120/208v panel with a #12 black, white, and green THHN from a 20 amp QOB breaker. Will this breaker likely trip if a ground fault occurs at the receptacle if the system bonding jumper was not installed at Transformer T3 and explain why
No, Ground fault current will not have a low impedance path to return to the source and facilitate operation of the circuit breaker
Transformers operate on the principal of
Mutual Induction
According to TBL 310.16 @ 75 degrees C, what is the maximum current allowable for 300MCM THHN CU, and is this properly sized for the secondary conductors that land on a 225 Amp Molded Case Circuit Breaker
285 amps, Yes
What type of overcurrent is a ground fault
Short circuit