WorksheetsNCCER Electrical Module 7
Total questions: 24
Worksheet time: 12mins
A self-contained meter installation refers to _____.
CT metering
a multiple meter enclosure
a single meter enclosure
meter enclosures with a main disconnect
The winding of a transformer that is connected to the load is known as the _____.
capacitive winding
secondary winding
primary winding
power winding
Conductors connected to the high leg of a four-wire delta system should be color-coded
_____.
red
orange
green
black
The components installed to increase the power factor and decrease the cost of electricity
caused by large inductive loads are _____.
rectifiers
diodes
capacitors
resistors
To ensure maximum safety in a control transformer, the secondary control circuit is _____.
isolated from the primary line circuit
connected to an autotransformer
controlled by taps
less than 120V
The walls and roof of a transformer vault must have a minimum fire resistance of _____.
30 minutes
1 hour
2 hours
3 hours
The type of transformer that can be ventilated, air-cooled, or sealed is a(n) _____
dry-type transformer
nonflammable fluid-insulated transformer
oil-insulated transformer
less-flammable liquid-insulated transformer
Capacitors are covered in _____.
NEC Article 402
NEC Article 424
NEC Article 440
NEC Article 460
Special rules apply to transformers rated higher than _____.
240V
480V
600V
1,000V
The installation of resistors and reactors is covered in _____.
NEC Article 424
NEC Article 440
NEC Article 470
NEC Article 480
A transformer can be checked for shorted turns using a _____.
VOM set to measure resistance
VOM set to measure current
TTR tester
megger
The insulating oil in a liquid-filled transformer should be regularly tested for _____.
conductivity
dielectric strength
acidity
water content
When testing dry-type transformers, check for cracked insulators on transformers over
_____.
240V
480V
600V
1,000V
The symptom of a partial short in the secondary winding of a transformer would MOST
likely be _____.
overheating
no power to the secondary
an ohmmeter reading of infinite resistance
zero voltage across the input terminals
Refer to the figure provided. A multi-tap transformer has 1,620 turns in the primary. There
are 40 turns between each tap. Taps 6 and 3 are connected. Which taps must be connected to
reduce output voltage by 5%?
5 and 4
6 and 2
7 and 2
7 and 4
Refer to the figure provided. Which taps should be connected to increase the secondary
voltage by 5%?
5 and 2
5 and 4
7 and 2
7 and 4
If there are 20 turns in the primary and only 10 in
the secondary and the transformer operates at
120V, the voltage in the secondary is _____.
480V
240V
120V
60V
The least efficient type of transformer is the _____.
open core
closed core
shell type
mitered core
Capacitor circuit conductors must have an
ampacity of not less than _____.
135% of the rated current of the capacitor
150% of the rated current of the capacitor
175% of the rated current of the capacitor
200% of the rated current of the capacitor
Dry-type transformers rated at 1121⁄2kVA or less
may be located out in the open provided they are
separated from combustible material by a distance
of _____.
6" (150 mm)
8" (200 mm)
10" (250 mm)
12" (300 mm)
If the power factor is improved by the addition of a
capacitor, the motor running overcurrent device
must be selected based on the _____.
reduced current
full-load current
125% of the locked-rotor current
200% of the full-load current
Except for motor starting service, insulated
conductors used for connections between resistors
and motor controllers must be rated at not less than
_____.
30°C (86°F)
60°C (140°F)
75°C (167°F)
90°C (194°F)
A transformer reads zero volts across the output
terminals. The cause is most likely _____.
an open circuit
a partially shorted winding
a ground fault
insulation breakdown
When performing maintenance on dry-type
transformers, check for cracked insulators on
transformers over _____.
240V
480V
600V
1,000V
