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ELO 21 chapter 14,15,19,20|Study Hacks:92 Key Questions for Effortless Learning Study Solutions: Clear Answers for Confident Exam Prep$7.99
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ELO 21 chapter 14,15,19,20|Study Hacks:92 Key Questions for Effortless Learning Study Solutions: Clear Answers for Confident Exam Prep
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Module
ELO 21 chapter 14,15,19,20
Institution
ELO 21 Chapter 14,15,19,20
A center-tapped 120/240 V secondary coil has the two parts of the coil inside the tank arranged in parallel. What would be the voltage between the X1 and the X3 terminals? - ️️Placing the two secondary coils in parallel allows the complete coil to be used to provide 120 V. The voltage between X...
ELO 21 chapter 14,15,19,20|Study
Hacks:92 Key Questions for Effortless
Learning
A center-tapped 120/240 V secondary coil has the two parts of the coil inside the tank arranged in
parallel. What would be the voltage between the X1 and the X3 terminals? - ✔ ✔ Placing the two
secondary coils in parallel allows the complete coil to be used to provide 120 V. The voltage between X1
and X2 would measure 120 volts, but between X1 to X3 would measure zero because nothing would be
connected to X3.
A customer pays a utility more per kWh when power is supplied at a primary voltage. (true or false) - ✔
✔ false
a large inductive load causes the power factor to go ______ - ✔ ✔ down
A transformer coil must have a potential difference across it in order to operate. What two types of
connections are possible to get a voltage across a transformer coil? - ✔ ✔ Wye or delta (parallel or
series).
A transformer with a 240 V secondary has a 60-to-1 turns ratio. What is the primary voltage feeding this
transformer? - ✔ ✔ 240 × 60 = 14.4 kV
A voltmeter can be used to verify that a socket-based meter will not be plugged into a short circuit. (true
or false) - ✔ ✔ true
An insulated or bare jumper should be carrying at least________percent of the load current before
cutting a conductor. - ✔ ✔ 30-33%
At the main panel, the phase-to-phase voltage readings of a delta 240 V service are lower than normal
and one phase-to-phase voltage reading is 0 V. For example, the readings are 210 V, 210 V, and 0 V.
What is the likely cause? - ✔ ✔ When one phase of a primary feeder loses power, the voltage at a
wye-delta transformer bank will have a reduced voltage on two of the phase-to-phase readings and 0 V
on the third phase-to-phase reading.
Can a single-bushing transformer be installed on a delta circuit? - ✔ ✔ No, the primary coil is
connected phase-to-phase and needs two insulated bushings.
Can the wye secondary of a wye-wye bank be connected to the same bus as the wye secondary of a
delta-wye bank of the same secondary voltage? - ✔ ✔ There is always an angular displacement or
phase shift with a wye-delta or a delta-wye transformer bank. The secondary will be 30° out of phase
with the primary. This means that a wye secondary of a wye-wye bank, which has a 0° angular
, displacement, cannot be connected in parallel with a wye secondary of a delta-wye bank, which has a
30° angular displacement.
Can two phases of a delta primary supply a three-phase, open-delta service? - ✔ ✔ To feed an open-
delta three-phase secondary service, three primary wires are needed. A wye primary would need two
phases and a neutral, and a delta primary would need three phases.
chapter 15 - ✔ ✔ ...
chapter 18 - ✔ ✔ ...
chapter 19 - ✔ ✔ ...
Energy consumption is the volts × amperes used by a customer. What is the largest variable measured
by a kilowatt-hour revenue meter? - ✔ ✔ amperes
How can ferroresonance be prevented when energizing a three-phase transformer bank? - ✔ ✔ Use
a three-phase gang switch.
Keep some load on the transformer.
Temporarily ground the floating neutral.
How can one CT be used to meter a 120/240 V three-wire service? - ✔ ✔ Both 120 V conductors go
through one CT. To have the current in the two opposite polarity 120 V legs go through the CT in the
same direction, the two wires go through the CT from opposite directions. The current from the two legs
adds together to double the secondary current.
How can the probability of a voltage surge be reduced while working with live-line tools on a
transmission line?
Answer text - ✔ ✔ block the automatic reclosure on all circuit breakers connected to circuit, do not
work when lighting is in the area
How can the second point of contact be eliminated when doing rubber-glove work? - ✔ ✔ isolate all
secondary points of contact. (cover-up, PPE)
How does a set of capacitors installed on a distribution feeder benefit the electrical system? - ✔ ✔
Installing a capacitor is the most economical way to improve the voltage on a feeder and also benefit
the whole electrical system. When the power factor of the circuit improves, there is less apparent power
needed to feed the load and, therefore, less current and less voltage drop. Capacitors can be in a
substation or downstream on a distribution circuit.
How many elements are in a meter that is normally used in a three-wire service? - ✔ ✔ Two,
typically, energy can be metered with one less element than the number of wires in the service.
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