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Transformers 1 Flashcards | StudBud
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Transformers 1
Transformers 1
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Answers
1
A ___?___ draws current in a waveform that matches the shape of the voltage waveform.
Harmonic filter
Capacitive load
Non-linear load
Linear load
2
Which of the following shows the primary Wye, higher voltage-secondary Delta, lower voltage.
Empty choice
Empty choice
Empty choice
Empty choice
3
A harmonic is a voltage or current at a frequency that is an integer multiple of the fundamental frequency.
False
True
4
We measure the power
consumed
by a load in?
Ohms
Watts
Amps
Volts
5
When an increase in flux density is no longer possible, the magnetic circuit___?___
will soon explode
no longer supports the core
has reached a point of saturation
will need a capacitor
6
Describe the primary and secondary transformer connections.
Primary-Wye Secondary- Wye single voltage
Primary-Wye. Secondary-Wye single voltage.
Primary-Delta Secondary-Delta Single voltage.
Primary-Delta Secondary-Wye Single voltage
7
This type of transformer is called___?___
Toroidal
Shell
Core
Center winding
8
Three phase DC is normally generated by utilities
True
False
9
The total power in the diagram below will deliver?
240 volts to load 1 & 2
120 volts to load 1 & 2
240 volts to a single load
120 volts to a single load
10
Phasor rotation is the order in which___?___
Each phase crosses zero
Each phase hits its most positive peak.
Each phase hits its most negative peak.
Each winding of a transformer reaches saturation
11
The product of a circuit’s voltage and current is called___?___
Reactive power
True Power
None of these
Apparent Power
12
Ferromagnetic materials are ______?_______
Easily converted from solid to gas
Found in plastic utensils
Not easily magnetized
Easily magnetized
13
Waveform distortion can happen when?
Transformers are operated below the point of saturation
Ultraviolet rays interfere with normal operation of the transformer
Transformers are operated at the point of saturation
The waveforms of a three phase circuit crash into each other
14
____ is Power loss due to currents that are induced into the metal structure of the transformer from the magnetic field.
Eddy current loss
Hysteresis loss
Magnetic coil loss
Voltage drop
15
The coils turns ratio will determine if the transformer is a?
Delta or Wye
Step up or step down
Resistive or Conductive
Positive or Negative
16
Total demand distortion is the ___?___ of the ___?___ to the maximum current load.
Ratio / current harmonics
Amount / Voltage
Frequency / Waveform
Displacement / Reactance
17
The strength of the electromagnetic field is directly related to the___?___
Turns ratio
Current
Voltage
Capacitive reactance
18
Inductance is the ability of a device or circuit to store energy in a magnetic field.
False
True
19
A passive harmonic filter uses___?___ that are tuned to remove harmonic frequencies.
Resistors and LED’s
Carbonadium and Adamantium
Capacitors and inductors
Hemp and steel wool
20
Excess heat in a transformer is caused by___?___
Resistance in the transformer windings.
A high demand factor
Harmonics
Waveform displacement
21
These allow for the output voltage of a transformer to be raised or lowered___?___
Resistors
Coil taps
Adjustment lines
Insulators
22
A harmonics mitigating transformer works by combining waveforms where the positive part of a waveform___?___
Adds to the negative part of another waveform, resulting in cancellation
Adds to the positive part of another waveform resulting in heat.
Subtracts from the positive part of another waveform.
Subtracts from the negative part of another waveform.
23
Magnetism is caused by a magnetic field and is described as?
A force that acts at a distance.
The property in a circuit which opposes change.
The ratio of change in an electric charge.
The property of a conductor that causes EMF.
24
A power supply that has an internal control circuit that
switches
the load current ON and OFF for stable output voltage
Duel trace power supply
Single emitter double collector power supply
low VOC power supply
Switched-mode power supply
25
Using an AC voltage source as opposed to a DC source will strengthen the magnetic field of an electromagnet.
False
True
26
A dry type transformer uses___?___ to cool the coils.
Oil
Powder
Air
Water
27
A ballast provides start-up voltage and maintains constant current through a lamp.
True
False
28
Self-induction is the ability of an ___?___ in a circuit to generate___?___which opposes change in current.
Motor / work
Capacitor / Capacitive reactance
Inductor / Inductive reactance
Conductor / Phase shift
29
Coefficient of coupling is also referred to as___?___
Mutual inductance
Flux expansion
Hysteresis effect
Phase loss
30
Magnetomotive force distributed over the length of a magnet is called?
Magnetic field intensity
Skin effect
Magnetic attraction
Magnetic reactance
31
Over current devices for industrial and commercial operations and ___?___ operate in a similar way.
Electrical distribution system shut off devices.
Commercial over voltage devices
Industrial metering devices
None of these
32
Transformers are rated in kVA because ____ represents the total power (current x voltage) the transformer can supply.
apparent power
reactive power
true power
magnetomotive force
33
Power should be removed from transformers before making tap changes.
True
False
34
Pure Iron should be used as a transformer core to maintain the highest flux density before saturation occurs.
True
False
35
"Lights-out" is a method of?
Powering down a transformer
lock-out tag-out
testing a ballast
synchronizing generators
36
The line voltage is the voltage that is measured___?___
Line to line
Line to neutral
Line to ground
Line to the equipment frame
37
The number of turns, strength of the magnetic field, and ___?___ determine the voltage produced by generators.
Speed of rotation of the rotor
Exciter type
Type of load
None of these
38
The amount of harmonics on a line compared to the frequency of 60 HZ is called
Total harmonic balance
Total harmonic distortion
Total demand power factor
Total demand balance
39
This type of transformer is called___?___
Toroidal
Core
Shell
Disc
40
Permanent magnets might be demagnetized by a ___?___
A stronger magnet
Sharp blow
Sodium hypochlorite
Extreme cold
41
A permanent magnet can ____?___
Also be used as an electromagnet
Not hold its magnetism for very long.
Hold its magnetism for long periods of time.
Have two north poles
42
Magnetomotive force is measured in___?___
Watt-turns
Volt-turns
Amp-turns
Lines of flux
43
Conductors wrapped into a coil will create a?
Weak magnetic field
Strong electromagnetic field
non-linear load
Capacitive charge
44
Current flow through individual windings is called___?___
Winding voltage
Line current
Winding current
Linevoltage
45
The line current in a balanced 3 phase delta system is equal to___?___ times the current in one of the coils.
606
.49
1.73
3.46
