Transformers
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Commercial Services
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Motor Calculations
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100
Core type most used
What is closed core
100
Transformer connection for a 120/240, 3Ph, 4W
What is midpoint grounded delta
100
What is a bar type current transformer
100
Typical voltage for small commercial services
What is 120/240, single phase
100
12 Leads
What is a delta connection
100
9 Leads
What is a wye connection
200
Both primary and secondary are on a common winding
What is an autotransformer
200
Most common core assembly method
What is mitered
200
Disconnect installed before the utility meter
What is cold sequence
200
EGC allowed to be smaller than NEC table 250.122
When part of a motor circuit
200
MSCP
What is Motor Short Circuit Protector
200
Two things that determine the synchronous speed of a motor
What is frequency and number of poles
300
TTR is 1:4 and voltage applied is 120volts. The output voltage is ?
What is 480 volts
300
KW/KVA
What is power factor
300
Metal enclosure containing factory mounted bus bars
What is busway
300
Final component of a commercial electrical service
What is a panelboard
300
Max motor rating for more than 1 motor on a single branch circuit
What is 1 HP
300
Minimum disconnect rating for a motor with a full load rating of 100 AMPS
What is 115 amps
400
Three things that need to be the same to parallel transformers
What is winding configuration, voltage and impedance
400
Phase shift on a delta to wye transformer connection
What is 30 degrees
400
Minimum depth of service conductors in conduit to be considered outside the building
What is 18"
400
If a service has more than six disconnects, what is required
What is a main disconnect
400
Max feeder thermal magnetic circuit breaker rating for a group motor load with FLA's of 50, 25 15 and 10
What is 175 amps
400
Maximum HP load rating for a 10 HP motor with a service factor 1.25
What 12.5 HP
500
Percentage capacity difference three transformer delta connection and two transformer open delta connection using the same transformer ratings
What is 57.7%
500
Transformer connection that will have A to ground 480v, B to ground 480v and C to ground 0v
What is a corner grounded delta
500
Kilowatt-hours indicated 
What is 1,657
500
A bussed wireway rated 800 amps or larger must have a short circuit interrupting capacity of ____?
Bussed wireways do not have an interrupting capacity
500
Min feeder ampacity for a group motor load with FLA's of 50, 25, 15 and 10
What is 112.5 amps
500
Which one is the lower voltage motor connection
What is the left