Turns Ratio Worksheet: Transformer Turns Ratio and Input/Output Problems, 2 primary windings, delta, wye,, Motor Drives (12+13), Vocabulary on Transformers (for Electrical Machines & Drives), Drive mechanism and Transformers, Transformer Review, Chap...
When troubleshooting a contactor or motor starter, the voltage is acceptable if the voltage reading is within _____% of the motor voltage rating.
10
In a DELTA system, the coil voltage is 7,200 volts. What is the system voltage?
7,200 Volts
Short
A(n) ______ circuit is a circuit in which current takes a shortcut around the normal path of current flow.
Dead
A(n) ________ short is a short circuit that opens the circuit as soon as the circuit is energized or when the section of the circuit containing the short is energized.
Open
A(n) _________ circuit is an electrical circuit that has an incomplete path that prevents current flow.
How are the secondary winding-ends tagged?
A, B, C, D
A nameplate reads 12,470GRDY/7,200. How many primary bushings does this transformer have?
One H1; the other end of the primary winding is a tank ground
Lower
One method to diminish the harmful effects of long lead lengths between an electric motor drive and a motor is to _____ the carrier frequency.
True
Service factor is a multiplier that represents the percentage of extra load that can be placed on a motor for short periods of time without damaging the motor.
The T-frame used with a 3 phase manual contactor is activated by a _____ mechanism.
pushbutton
The _____ indicator on a trip indicator informs the operator or electrician why the unit is not operating and that it is potentially capable of restarting with an automatic reset.
red
Two-wire control is normally used for _____ installations where an immediate return to service after a power failure is required.
remote or inaccessible
A(n) _____ is used to increase or decrease the strength of the field or armature in a DC shunt motor.
rheostat
In a stepper motor, the permanent magnet is called the _____ or armature.
rotor
Terminal markings S1 and S2 always indicate the _____ field leads.
series
A(n) _____ circuit is a circuit in which current takes a shortcut around the normal path of current flow.
short
To help reduce damage to switch contacts, a(n) _____ circuit is used to protect the switch.
snubber
Because the stator coils are turned on and off rapidly to control a stepper motor, _____ switches are used.
solid-state transistor
The requirements a motor must meet in controlling a load include work, force, torque, and horsepower in relation to _____.
speed
The direction of shaft rotation is controlled by the polarity of the produced magnetic field in the _____.
stator coil
AC contactor assemblies are made of laminated _____, while DC assemblies are solid.
steel
when current flows through both windings in the same direction the polarity is_______
subtractive
In a DC shunt motor, if the _____ to the armature is reduced, the speed is also reduced.
voltage
False
Control wiring should be installed in the same conduit as power wiring.
False
Electric motor drives cannot introduce power quality problems into a power distribution system.
True
Electric motor drives operate satisfactorily only when connected to the proper power supply.
low
Electric motors that are continuously operated at _____ speeds must be derated or provided with auxiliary cooling.
False
Electrical loads operating at lower rated voltages are more likely to be damaged than loads operating at higher rated voltages.
The wires extending from the shunt field of a DC shunt motor are marked _____.
F1 and F2
False
Grounding of an electric motor drive provides equal potential between all metal surfaces and a high-impedance path to activate overcurrent devices.
Anode
Positive electrode
False
Power wiring is all external wiring connected to an electric motor drive, excluding the line and load conductors.
What part of the transformer helps to relieve any buildup of gas inside the tank?
Pressure relief valve
Which side of the transformer is the source side?
Primary Side
Or
What type of circuit logic is developed when two NO switches are connected in parallel?
And
What type of circuit logic is developed when two NO switches are connected in series?
0V
When a switch is used to control a lamp or other load in a 24VAC control circuit, what is the voltage that would be measured across the switch when the switch is closed and the load is ON?
24V
When a switch is used to control a lamp or other load in a 24VAC control circuit, what is the voltage that would be measured across the switch when the switch is open and the load is OFF?
NO and Parallel
When additional switches are to be wired into a control circuit to produce additional START functions, are NO or NC contacts used and are they connected in series or parallel?
NC and series
When additional switches are to be wired into a control circuit to produce additional STOP functions, are NO or NC contacts used and are they connected in series or parallel?
Black
When connecting a DMM to L2 of a control circuit, which color DMM test lead is always used?
What does "Alley-Cat, Bad-Dog" mean?
When paralleling the windings for a WYE secondary, open the lid and connect A and C together to X1, and then B and D together to
two
When using PWM with AC voltage, _____ IGBT(s) is/are used for each phase.
To identify and separate the different component parts included on the individual pieces of equipment
Why are manufacturer's terminal numbers added to a control circuit?
To trace the action of a circuit in complex line diagrams.
Why are numerical cross-reference numbers added to a control circuit?
To keep track of the different wires that connect the components in the circuit
Why are wire reference numbers added to a control circuit?.
Metal
Wiring for digital signals, analog signals, and serial communication signals should be installed in separate _____ conduits.
_____ is produced when a force overcomes a resistance.
Work
A _____ rotor is a condition when a motor is loaded so heavily that the motor shaft cannot turn.
locked
A(n) _____ is the arrangement of contacts in such a way that both sets of contacts cannot be closed at the same time.
mechanical interlock
A(n) _____ should be used for more accurate testing of insulation.
megohmmeter
The electron flow motor rule states that the _____ points in the direction of the electron current flow in the conductor.
middle finger
Stepper motors are used in applications that require precise control of the position of the _____.
motor shaft
It simplifies the understanding of the function of a circuit.
why are line numbers added to a control circuit?
Manual contactors are normally used _____.
with lighting circuits.
_____ primaries are three phase lines with a neutral
wye
Pilot lights
______ signal an operator that any one of a sequence of events may be taking place.
troubleshooting
_______ is the systematic elimination of various parts of a system, circuit, or process to locate a malfunctioning part.
AND
_______ logic is used in industry when two NO pushbuttons are connected in series to control a solenoid.
circle
_______ the wire reference numbers is a common method to help differentiate wire reference numbers from other numbering systems.
Manual Automatic and Manual
________ are signal conditions
Line (ladder)
________ diagrams are one of the oldest and most common methods of illustrating and understanding basic logic functions.
NOT
________ logic is used in a circuit when a pilot light is used to show that an operation has stopped.
OR
________ logic is used in industry when an NO pushbutton and an NO temperature switch are connected in parallel.
Memory
_________ circuits are also known as holding or sealing circuits.
NAND
_________ logic is an extension of NOT logic in which two or more NC contacts are connected in parallel to control a load.
NOR
_________ logic is an extension of NOT logic in which two or mote NC contacts in series are used to control a load.
NOT
__________ logic has an output if the control signal is OFF.
Step down transformer
a transformer that decreases voltage when the primary voltage is greater than the secondary voltage
step-up transformer
a transformer that increases voltage when the secondary voltage is greater than the primary voltage
Contactor and magnetic motor starter modification devices include additional electrical contacts, power power poles, pneumatic timers, transient suppression modules, and _____.
control circuit fuse holders
wye primaries never have a neutral
false
A _____ alloy is a metal that has a fixed temperature at which it changes directly from a solid to a liquid state.
eutectic
a phase rotation indicator is used to check system voltage.
false
all single phase transformers 200kva and under with high voltage winding voltage 8660v amd lower are subtractive polarity
false
in a grounded primary wye system the ground us connected to c phase
false
when connecting a customers service to a three phase transformer bank you do not have to worry about phase rotation.
false
A DC motor consists of _____ windings, an armature, a commutator, and brushes.
field
The intensity of the magnetic field and the amount of current in a conductor are normally changed to increase the _____ on the conductor.
force
bushings hold and insulate the windings from_________ on the transformer tank
grounding out
A(n) _____ coil converts the excess current drawn by a motor into heat, which is used to determine whether the motor is in danger.
heater
the letter ___ represents the high side of the transformer
high side
single phase transformers have a ____ voltage winding and a ______ voltage winding
high, low
The _____ of a motor determines the size of a load that the motor can operate and the speed at which the load turns.
horsepower
A(n) _____ motor protector is an overload device located directly on or in a motor to provide overload protection.
inherent
A motor that is starting draws a tremendous _____ current (normally six to eight times the running current) when the circuit is closed.
inrush
Additional NC contacts are used to turn on additional loads anytime a contactor or starter is OFF, as well as to provide electrical _____.
interlocking
A DC _____ motor should always be connected directly to the load and not through belts, chains, etc.
series
An advantage of _____ contacts is that the oxide (rust) that forms on the metal is an excellent conductor of electricity.
silver alloy
The _____ is the base unit of electrical power.
watt
Nor
what type of circuit logic is developed when two NC switches are connected in series?
Idler
wheel between two other wheels
the low side is represented by the letter ___
x
Spindle
Also known as shaft goes between the wheels
Horsepower (HP) is a unit of power equal to _____ lb-ft per min.
33,000
Open
A switch in the OFF position is A(n) _______ circuit.
A spring placed behind the brush forces the brush to make contact with the _____.
commutator
Speed Ratio Equation
Speed of driver/speed of driven
Types of drive mechanism
The belt drive The chain drive the gear
Which type of connection is phase-to-phase? DELTA or WYE?
Delta
It is estimated that every _____ C rise over normal ambient temperature ratings for insulation can reduce the life expectancy of a motor by almost a year.
1
If 100 volts is supplied to a primary coil wound 100 times, and the secondary coil with only 10 wraps is placed near it, how many volts will be induced?
10 volts
If a motor has an FLC rating of 10 A and an SF of 1.15, the excess short-term current equals _____ A.
11.5
In a WYE system, the coil voltage is 7,200 volts. What is the system voltage?
12470 Volts
A commutator rotates in _____ degree increments.
180
How many "power" transformers are there in a closed-DELTA bank?
2
Transient suppression modules normally consist of resistance/capacitance (RC) circuits and are designed to suppress the voltage transients to approximately _____% of peak coil supply voltage.
200
What is the hot-leg-to-hot-leg voltage (p-p) in a standard 120/208 3ph service?
208 Volts
What is the power leg voltage in a 120/240 3ph service?
208 Volts
A _____ V, 1 phase power source has two hot wires, L1 and L2 (ungrounded conductors), and no neutral.
230
What is the power-leg-to-hot-leg voltage in a 120/240 3ph service?
240 Volts
Overload relay devices are normally rated to trip at a specific current when surrounded by an ambien temperature of _____ C.
40
read-only
A _____ parameter is a parameter value that can be displayed, but not set or changed.
Load
A __________ is the electrical device in a line diagram that uses the electrical power from L1 to L2.
True
A bearing current is the result of induced voltage in the motor rotor created by the electric motor drive.
True
A bypass contactor is a contactor that allows line power to a motor that is normally controlled by an electric motor drive.
True
A capacitor is an electronic device specifically designed to store a charge of energy.
secondary cell
A cell that can be recharged
Transformer
A device that is used to transfer electrical enrgy from one circuit to another by electromagnetic induction
forward-biased
A diode allows current to flow only when it is _____.
True
A disconnect is a device that isolates an electric motor drive and/or motor from the voltage source to allow safe access for maintenance or repair.
False
A fixed resistor is a resistor that contains fixed tap points of different resistances.
True
A fly-back diode is a diode placed across a transistor to prevent high voltage spikes produced by the collapsing magnetic field of the motor windings.
Gear train
A group of 2 or more gears
True
A heat sink is a device that conducts heat away from an electrical component.
True
A line reactor is installed as close as possible to the input of an electric motor drive.
True
A multiple-motor installation requires that all the motors have the same NEMA design letter.
parentheses
A numerical cross-reference system consists of numbers in _______ to the right of the line diagram.
Emergency Stop
A(n) _____ is used where accidental contact with moving equipment, or the unintended flow of product, can result in physical injury or property damage.
nonlinear
A(n) _____ load is any load where the instantaneous load current is not proportional to the instantaneous voltage.
False
A rectifier changes DC voltage into AC voltage.
True
A semiconductor device is an electronic device that has electrical conductivity between that of a conductor and that of an insulator.
Electrolyte
A substance that dissolves in water to give a solution that conducts electric current which has two electrodes
Solid-State
A(n) _____ switch is a device that uses electronic components to open and close circuits at a precise point in time to control current flow and voltage levels.
Gear
A toothed wheel fixed in machines to make different parts move at different speeds and in differnt directions
a. 40:15 or 8:3 ratio b. step down
A transformer has 15 turns in the secondary and 40 turns in the primary. a. what is the turn ratio? b. is this a step up or step down transformer?
a. 200:100 or 2:1 ratio b. step up
A transformer has 200 turns in the secondary and 100 turns in the primary. a. what is the turn ratio? b. is this a step up or step down transformer?
a. 30:60 or 1:2 ratio b. step down
A transformer has 30 turns in the secondary and 60 turns in the primary. a. what is the turn ratio? b. is this a step up or step down transformer?
a. 200:400 or 1:2 ratio b. step down
A transformer has 400 turns in the secondary and 200 turns in the primary. a. what is the turn ratio? b. is this a step up or step down transformer?
Kilovolt ampere
A unit of electrical power equal to 1000 volt amperes
3
A voltage difference greater than _____ % between no-load and full-load conditions indicates that the electric motor drive is underpowered and/or overloaded.
False
A voltage sag is a high-energy, high-voltage, short-duration spike in an electrical system.
Open Loop
A(n) _____ drive is an electric motor drive that operates without any feedback to the drive about motor speed.
Integrated Power Module
A(n) _____ is a grouping of separate parts designed to perform a set of function or task, such as providing a time delay, power gain, or filtering a signal.
Insulated Gate Bipolar Transistor
A(n) _____ is a high power switching device that can switch high currents and high voltages.
Encoder
A(n) _____ is a sensor that produces discrete electrical pulses during each increment of shaft rotation.
Silicon Controlled Rectifier
A(n) _____ is a solid-state device with the ability to rapidly switch high currents.
capacitor
A(n) _____ is an electrical device designed to store electrical energy.
Surge Suppressor
A(n) _____ is an electrical device that provides protection from transient voltages by limiting the level of voltage allowed downstream.
Diode
A(n) _____ is an electronic device that allows current to pass through in only one direction.
OR
Additional start pushbuttons are connected in parallel using _______ logic with the existing start pushbuttons.
NOR
Additional stop pushbuttons are connected in series using _________ logic with the existing stop pushbuttons.
Three
All circuits are composed of _________ basic section(s).
True
An SCR is a solid-state device that controls current according to the amount of voltage applied to the base.
transformer
An electrical machine that transfers electrical energy between two or more circuits through electromagnetic induction.
Digital
An example of A(n) _________ process is a standard light switch that has only two positions: fully ON or fully OFF.
Top
An integrated circuit's notch indicates the ________ of the chip.
True
As the length of conductors increases and/or an electric motor drive's output carrier frequency increases, the voltage spikes become larger.
_____ wear faster than any other component of a DC motor.
Brushes
True
Capacitors oppose a change in voltage and coils oppose a change in current.
What is a "power leg" and what is it used for?
Check to see if it has a ground strap to the case. If it does, remove it or you will short the secondary windings out.
What is a "CSP" transformer and what transformer parts are specific to a CSP?
Completely Self Protecting, and there is an internal primary fuse link and a secondary breaker
Chain drive
Combines the sprocket and chain that mesh together to produce a positive mechanical force
Worm gear
Connects shafts at right angles to each other
speed
Controlling the frequency to an AC motor controls the _____ of the motor.
WYE or DELTA? 240/480 3 ph service
DELTA
Chemical Cells
Devices used to convert chemical energy to electricla energy
a. 10,000 volts b. step down
Determine the input of a transformer if the turn ratio is 200:400 and the output voltage is 5,000 volts. a. input voltage? b. is this a step up or step down transformer?
a. 200 volts b. step up
Determine the input of a transformer if the turn ratio is 500:1 and the output voltage is 100,000 volts. a. input voltage? b. is this a step up or step down transformer?
a. 60 volts b. step up
Determine the input of a transformer if the turn ratio is 6:1 and the output voltage is 360 volts. a. input voltage? b. is this a step up or step down transformer?
a. 60 volts b. step down
Determine the output of a transformer if the turn ratio is 300:600 and the input voltage is 120 volts. a. output voltage? b. is this a step up or step down transformer?
a. 14,666 b. step up
Determine the output of a transformer if the turn ratio is 400:3 and the input voltage is 110 volts. a. output voltage? b. is this a step up or step down transformer?
a. 120,000 volts b. step up
Determine the output of a transformer if the turn ratio is 500:1 and the input voltage is 240 volts. a. output voltage? b. is this a step up or step down transformer?
Top
Each line in a line diagram should be numbered starting with the _________ line
There are two ways to deliver a three-phase service to a customer. What are they?
Either with a three-phase transformer or interconnected single-phase transformers.
What are "bayonet" fuses used for?
Energizing and de-energizing the secondary side of a transformer
The types of belt drive are
Flat belt Round belt Vee belt
Gear Ratio Formula
Gear ratio = Driven teeth / Driver teeth(Na/nb)
single
In residential and small commercial locations, only a(n) _____-phase power source is available.
False
Higher carrier frequencies cause smaller power losses in an electric motor drive.
Parallel with coil or use NO contacts
How is a lamp added into a control circuit so it is ON anytime the motor is ON?
As many as the switch and other controls amp rating allow
How many loads can be connected in parallel per line in a control circuit in which a switch is used to control the load(s)?
one
How many loads can be connected in series per line in a control circuit in which a switch is used to control the load(s)?
False
If control and power wiring must cross, they should cross at a 45 degree angle.
A coil of wire will become energized if it is placed close to another coil of wire that is attached to AC power. What is this phenomenon called?
Induction
True
Inductive loads such as solenoids or the coils of relays and contactors are a common source of electromagnetic interference (EMI) in electric motor drives.
Every effort should be made to select transformers with the same ___________ when paralleling or banking.
Impedances
Drive
In a majority of electric motor drive applications, the _____ provides the overload protection.
What is meant by "Sames-Opposites"?
In an Open-WYE / Open DELTA, if the primary connects sames (H2s are tied and grounded), then the bottoms must connect opposites (X3 connects to X1); must be sames-opposites or vice versa.
Action
In most cases it is the operating coil in the circuit that is responsible for initiating the ________.
True
Inverter drives can typically control motor speed within +/- 1% of the set speed of the drive.
Current Source (CSI)
Inverter drives include variable voltage inverters, _____ inverters, and pulse width modulated inverters.
In an open bank, why would one transformer be bigger, and how is that transformer referred to?
It is larger in kVA because it provides power to the three-phase and the single-phase load; it is called the "lighter" or "lighting" pot
What consideration should be given to the X2 on the "power" transformer?
It is the third phase in a DELTA bank; it's phase-to-ground voltage serves nothing, but its phase-to-phase voltage feeds the three-phase load.
A nameplate reads 12,470GRDY / 7,200 volts. How would this connect to a 4160 / 7200 system?
It wouldn't; It is a single bushing transformer and must be connected as a WYE configuration.
True
Lightning strikes and utility switching cause high-energy-level transient voltages.
_____ overload relays are extremely quick to reset because they do not require a cooling-off period before being reset.
Magnetic
_____ are used to reduce the distance required and yet quench arcs quickly.
Magnetic blowout coils
Serial
Many electric motor drives have the capability to communicate with PLCs, other drives, and PCs via _____ communication.
False
Most electric motor drives are delivered from a manufacturer in NEMA type 4X enclosures.
False
Most people can hear a tone from a motor when it is in the 1 Hz - 3 Hz range.
430
NEC Article _____ is the main code source for electric motor drives.
Part 31
NEMA standard MG-1, Section IV, _____ provides an enhanced insulation requirement for electric motors, allowing compatibility with electric motor drives.
Cathode
Negative electrode
One
No more than ________ load(s) should be placed in any circuit line between the power lines L1 and L2.
Can an Open-WYE / Open-WYE serve a three-phase load?
No, Open WYE secondary only has two phases
In a 240 3ph-3wire service, what happens if one phase gets grounded?
Nothing. It becomes a corner ground, and the 3-phase service is still delivered. You can ground one time at any point in the service
If a transformer nameplate has only one number listed for a primary voltage rating, how should it be connected?
Phase to phase
A nameplate reads 7,200 / 12,470Y. How would this connect to a 7,200 / 12,470 system?
Phase-to-ground or WY
Engineers can choose from three different primary voltage designations when purchasing transformers. What are they?
Phase-to-phase only • Phase-to-phase or phase-to-ground • Phase-to-ground only
A nameplate reads 7,200 / 12,470Y. How would this connect to a 4160 / 7200 system?
Phase-to-phase or DELTA
Ohms
Resistors are classified by a resistance value in _____ and power dissipation value in watts.
True
Reverse bias is the condition of a diode when it does not allow current flow and acts as an insulator.
Which side of the transformer is the load, or customer's side?
Secondary side
True
Since the angle (timing) of the gate firing pulse can be changed, and SCR can vary voltage output.
_____ action is the principal operating mechanism for magnetic contactors.
Solenoid
Types of Gear
Spur gear Worm gear bevel gear
False
Static electricity cannot be discharged by human skin contact.
What does the term "open bank" mean?
That the wye or delta configurations are incomplete
Inverter
The DC bus section of a drive delivers the DC voltage to the _____ section for conversion back to AC voltage.
True
The DC bus voltage of an electric motor drive is typically about 1.4 times the AC supply voltage to a drive.
On a transformer nameplate that lists two primary numbers separated by a slash, which number is the actual primary coil rating?
The Smaller
Saturation
The _____ region is the maximum current that can flow in the transistor load circuit.
Signal
The ________ accomplishes no work by itself; it merely starts or stops the flow of current in that part of the circuit.
Decision
The ________ of a circuit adds, subtracts, sorts, selects, and redirects the signals from the control devices to the load.
Proper transformer selection starts by comparing two things. What are they?
The circuit and service voltages (on the work order) and the transformer voltage/kVA ratings
True
The converter section of a drive receives the incoming AC voltage and changes the voltage to DC.
What are the three main components of a transformer?
The core, the windings, and the insulating fluid
Simple
The dashed line method works well when the control contacts are close together and the circuit is relatively ________
Electrolysis
The decomposition of the electrolytes into its constituents ions(anion and cation) as a result of the passage of current
True
The final connection to the motor should be made with a short length of flexible conduit and standard wire.
False
The frequency applied to a DC motor controls the motor speed.
A transformer has a blue sticker that says "Non-PCB". What does that mean?
The insulating fluid is good; contains no Polychlorinated Biphenyls.
ON
The load is _________ all the time if no control device is included in a line.
False
The lower the carrier frequency, the closer the output current sine wave is to a pure fundamental frequency sine wave.
Complex
The numerical cross-reference method is used on _________ line diagrams.
DC Voltage
The output of a bridge rectifier is a pulsating _____ that must be filtered before it can be used in most electronic equipment.
Torque
The primary function of a motor is to produce _____ to safely drive the driven load connected to the motor.
star-delta transformers
The primary is connected in star fashion and the secondary is connected in delta fashion.
Voltage Drop
The primary limit to the distance between a magnetic motor starter and the motor is the _____ for the conductors
What information would you typically reference the nameplate for?
The primary voltage • Desired secondary voltage • kVA • Impedances are close enough for banking and paralleling • Weight of the transformer for rigging
turns ratio
The ratio of the number of turns on the primary coil of an electrical transformer to the number of the secondary, or vice versa.
Where is the X1 bushing on an additive transformer, as you face it?
The right of the X2
True
The saturation region is the maximum current that can flow in the transistor load circuit.
What is the "power" transformer?
The smaller of the transformers in the DELTA bank; it provides the third phase
What is a tap changer used for on a transformer?
The tap can adjust the voltage by changing the turns ratio. This ensures the proper secondary voltage is delivered to the customer
False
The three terminals of a silicon-controlled rectifier are the anode, cathode, and emitter.
You perform a continuity test on a transformer with two H-bushings. An audible sound is heard when reading between the H1 and the X1. What does this mean?
The transformer has a short between the primary and secondary windings; red tag and remove from inventory.
True
The two general categories of logic integrated circuits are the transistor-transistor logic family and metal-oxide-semiconductor family.
False
The type of enclosure used does not affect the temperature of an electric motor drive.
phase voltage
The voltage between the given phase and neutral
line voltage
The voltage between two lines
secondary winding
The winding connected to the load
primary winding
The winding connected to the supply
drive mechanism
The working part of a machine which transmits power or movement from one part to another
delta-wye transformers
They are common in commercial, industrial and high-density residential areas to supply three-phase distribution systems.
uses of gears
They can be used to transmit power They are used to change speed They enable cars move They change the direction of motion The ensure smooth running under varying speed
What must be done to the secondary coils in a DELTA-WYE bank?
They must be paralleled; AC-B
In a WYE-DELTA bank what must be done to the H2s on each transformer?
They must be tied together, but not grounded or connected to neutra
_____ control provides low-voltage release and low-voltage protection.
Three-wire
In a WYE-WYE bank, what must be done to the H2s on each transformer?
Tie them together and connect to neutral
In a WYE-WYE bank, what must be done to the X2s on each transformer?
Tie them together and connect to neutral
True
To control AC voltages, at least two transistors are used per phase.
underlined
To differenciate between NO and NC contacts, NC contacts are indicated as a number that is _________.
Why is it important to perform a continuity test on a transformer before installation?
To ensure the windings are connected properly and check for shorts
In a WYE-WYE bank, why is it important to parallel the secondary windings?
To get the full kVA rating from the transformer
_____ is exerted on an armature when it is positioned so that the plane of the armature loop is parallel to the field, and the armature loop sides are at right angles to the magnetic field.
Torque
_____ is the force that produces rotation.
Torque
State the polarity rule.
Transformers 200kVA and smaller, with a primary rating of 8,660 volts and below, will be rated additive. All other transformers will be subtractive.
True
Transistors have no moving parts and can switch ON and OFF quickly.
True
Transistors operate at much faster speeds than silicon-controlled rectifiers (SCRs), allowing higher switching frequencies.
Spur Gear
Transmits motion between parallel shafts
Bevel Gear
Transmits motion between shafts that are close
_____ state a problem, its possible cause(s), and corrective action(s) that may be taken.
Troubleshooting guides
series
Two loads must not be connected in _________ in one line of a line diagram.
3300
Typically, electric motor drives must be derated at altitudes above _____'.
11,000 volts
Using a transformer, calculate the missing factor for the following number of primary, secondary turns, and assuming no power loss occurs: primary voltage - 110 # primary turns - 200 # secondary turns - 20,000 secondary voltage - ?
22,000 volts
Using a transformer, calculate the missing factor for the following number of primary, secondary turns, and assuming no power loss occurs: primary voltage - 220 # primary turns - 100 # secondary turns - 1,000 secondary voltage - ?
10,000 turns
Using a transformer, calculate the missing factor for the following number of primary, secondary turns, and assuming no power loss occurs: primary voltage - 220 # primary turns - ? # secondary turns - 100 secondary voltage - 2.2
440 volts
Using a transformer, calculate the missing factor for the following number of primary, secondary turns, and assuming no power loss occurs: primary voltage - ? # primary turns - 5,000 # secondary turns - 500 secondary voltage - 44
50 volts
Using an autotransformer, calculate the missing factor for the following voltages, total number or tapped turns for the autotransformer, and assuming no power loss occurs: primary voltage - 100 # primary turns - 100 # tapped turns - 50 secondary voltage - ?
110 turns
Using an autotransformer, calculate the missing factor for the following voltages, total number or tapped turns for the autotransformer, and assuming no power loss occurs: primary voltage - 110 # primary turns - 220 # tapped turns - ? secondary voltage - 55
50 volts
Using an autotransformer, calculate the missing factor for the following voltages, total number or tapped turns for the autotransformer, and assuming no power loss occurs: primary voltage - 200 # primary turns - 400 # tapped turns - 100 secondary voltage - ?
440 volts
Using an autotransformer, calculate the missing factor for the following voltages, total number or tapped turns for the autotransformer, and assuming no power loss occurs: primary voltage - ? # primary turns - 880 # tapped turns - 110 secondary voltage - 55
Multiple
Vector drives cannot be used to operate _____ motors from the same drive.
What must be done before connecting the customer's load?
Verify the correct secondary voltage with an approved voltmeter
WYE or DELTA? 120/208 3 ph service
WYE
WYE or Delta? 277/480 3 ph service
WYE
Which type of connection is phase-to-neutral? DELTA or WYE?
WYE
Start and Stop a motor
What function does a JOG button perform in a control circuit?
Nand
What type of circuit logic is developed when two NC switches are connected in parallel?
False
When terminating shielded twisted-pair cables, the shield is terminated only at the device end.
First use volt meter to confirm that voltage is off then use ohm meter to check resistance.
When there is a short circuit in a control circuit, what function of the meter is used to test the circuit components before the faulty component is repaired and power is restored?
Jogging
____ is the frequent starting and stopping of a motor for short periods of time.
Speed
_____ control is not possible when operating in bypass mode.
Digital
_____ inputs consist of control devices that provide an on/off signal such as a selector switch.
VVI (Variable Voltage Input)
_____ inverter drives control an AC motor but produce a square wave instead of a sine wave.
Voltage Drop
_____ is the amount of voltage consumed by a device or component as current passes through it.
Carrier Frequency
_____ is the frequency that controls the number of times the solid state switches in the inverter section of a PWM electric motor drive turn ON and turn OFF.
Ambient Temperature
_____ is the temperature of the air surrounding a motor.
Plastic
_____ raceways are not recommended for electric motor drive installations because they do not provide shielding.
Inverter
_____ rated motors that have spike-resistant insulation reduce the damage caused by voltage spikes.
Metal Conduit
_____ serves as a shield, preventing conductors from radiating EMI and protecting conductors from any radiated EMI.
Base
_____ speed is the speed at which a motor develops rated horsepower at rated load and voltage.
Four
_____ transistors are required to control the direction of a DC motor.
Low
_____-energy-level transients cause malfunctions such as processing errors and damage to equipment over time.
Normally, only one _____ unit with one or two contacts is added per contactor or motor starter.
power pole
when current flows one way through low voltage winding and one way through high voltage winding polarity is _______
additive
when connecting three single phase transformers together to form a bank a relationship forms between the high voltage winding and the low voltage winding this is called__________
angular displacement
A DC series motor is a DC motor that has the series field connected in series with the _____.
armature
A(n) _____ overload relay is an overload relay that resets automatically.
bimetallic
Full-wave rectified power is obtained by placing a(n) _____ in an AC power line.
bridge rectifier
DC motors require more maintenance than AC motors because they have _____ that wear.
brushes
the primary and secondary lines connect to the transformers windings that exit the transformer through the ______
bushings
primary cells
cannot be recharged e.g dry cells and mercury cells
A _____ is an overcurrent protection device with a mechanism that automatically opens the circuit when an overload condition or short circuit occurs.
circuit breaker
Most DC motors are designed so that the brushes and the _____ can be inspected without disassembling the motor.
commutator
A commutator connects each armature winding to the brushes using _____ bars (segments) that are insulated from each other with pieces of mica.
copper
Originally, most knife switches were made of _____, which is required replacement after repeated arcing, heat generation, and mechanical fatigue.
copper
Motors operate on the principle that when a _____-carrying conductor is placed in a magnetic field, a force that tends to move the conductor out of the field is exerted on the conductor.
current
A _____ is used to change the amount of current flowing to a motor but reduces the current to a lower value for the overload relay.
current transformer
A _____ is a device used only periodically to remove electrical circuits from their supply source.
disconnect
A(n) _____ is a sensor (transducer) that produces discrete electrical pulses during each increment of shaft rotation.
encoder
For fully reliable motor protection, heat coils should be selected based on the motor _____ rating shown on the motor nameplate.
full-load current
a______ is a conductor when connected allows electricity to flow from one conductor to another
jumper
AC manual starters are selected based on phasing, voltage, starter size, enclosure type, and _____.
number of poles
a single phase trans will have _______ set of secondaries
one
A(n) _____ was an improvement made to the original design of a knife switch.
operating spring
Loose connections in the power circuit of contactors and motor starters cause _____
overheating
to identify three phase connections the industry uses graphic symbols called_____
phasor diagrams
The _____ that is produced by a motor depends on the strength of the magnetic field in the motor.
torque
a phasor diagram is a picture of a systems current and voltage at one given instant
true
because delta do not have neutral the transformer ground will only connect to the pole ground
true
branch circuits coming off wye primary consist of one phase and a neutral.
true
delta primarys are usually a three phase pine with no neutral
true
high voltage bushings have more insulating quality the low voltage bushings
true
phase rotation can be either clockwise or counter clockwise
true
the polarity is the direction the current flows through the low voltage in respect to the high voltage side of winding of any given moment
true
three phase pad mount transformers are single cabinet units
true
