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Units 2 & 3
Question | Answer |
---|---|
The heavier lines on electrical diagrams usually indicate the control circuit conductors | False |
In a ladder diagram components are arranged according to their physical position in the installation | False |
The conductors feeding to a large motor would be considered to be part of the control circuit | False |
When more than one electrical load is connected in a rung of a ladder diagram, the loads are normally connected in series | False |
Wires common to each other are usually identified by the same number | True |
If a control circuit is supplied from a grounded circuit, it makes no difference what side of the line is grounded | False |
Wiring diagrams are used when installing and tracing wires in electrical installations | True |
With low-voltage protection, when power is restored after a power failure, manual restarting is required | True |
No wires or components are normally shown on block diagrams | True |
The direction of rotation of a DC motor depends on the direction of the magnetic field and the direction of the current flow through the armature | True |
Motor terminal markings are usually used to tag only those terminals to which connections must be made from external circuits | True |
Single-phase AC motors are typically constructed in small horsepower sizes | True |
All 3-phase motors are wired so that the phases are connected in either Wye or Delta configuration | True |
The rated nameplate speed of a motor is its approximate speed with no load applied | False |
The motor nameplate Design letter is an indication of the motors torque speed curve | True |
A motor with a low power factor rating will draw less current for the same horsepower than a motor with a high power factor | False |
Two-wire control circuits are designed to protect against automatic restarting when power returns after a power failure | False |
Ladder diagrams show | the electrical connections |
The two basic parts of a typical motor circuit are the | control circuit and power circuit |
On a ladder diagram, all wires that connect to a common point are assigned | the same numbers |
Which of the following diagrams shows an electrical installation reduced to its simplest form | single-line diagram |
In a dual-voltage split-phase motor, the two run windings are connected in ___ for the High voltage operation | series |
When a split-phase motor is operated with a capacitor in series with one of the stator windings the | starting torque is higher |
The speed of an AC induction motor depends on the | voltage of the electrical power supply and number of poles built into the motor |
NEMA requires that the motor be able to carry their rated horsepower at nameplate voltage plus or minus | 10% |
Standard NEMA motor insulation classes are given by | alphabetic classification |
A motor nameplate indicates that the motor has a "service factor" of 1.25. This means that the | motor can on occasion safely develop 125% of its HP |
The nameplate of a motor indicates that its thermal protected. This means | the motor has a built in thermal device |
The plugging of a motor refers to | braking by reverse rotation |
With "low voltage protection" motor control is | a power failure disconnects service and when power is restored manual restarting is required |
Which of thhe following types of motor starters connects the motor directly to the supply line on starting? | full voltage starter |
Two-wired control circuits use a ___-contact type of control device | maintained |
A ladder diagram is a _____ representation of an electric circuit | schematic |
On electrical diagrams, conductors that cross each other and make contact are represented by a heavy ___ at the junction | dot |
For a ____ connection of loads, the voltage across load is the same as that of the applied voltage | parallel |
On a ladder diagram, a line is defined as a complete ___ from L1 to L2 that contains a load | path |
A wiring diagram is intended to show the actual ____ of all components | location |
Industrial applications use DC motors because the ___/____ relationship can be easily varied | speed/torque |
The rotating part of an AC motor is referred to as the ___; the stationary part is called the ____ | rotor, stator |
The phase rating of a motor is listed on the nameplate as ___,____,____ | DC, 1-phase, 3-phase |
The amount the motor winding temperature will increase above the ambient at full load is specified according to the nameplate _______ rating | temperature rise |
The two general classifications of motor enclosures are ____and ____ | open, totally enclosed |
Single-phase power is usually supplied to an industrial customer | False |
The higher the level of the distribution voltage, the more difficult and expensive it becomes to safely insulate between line wires, as well as from line wires to ground | True |
The switchboard is usually supplied from the panelboard | False |
Movement of the coils within a transformer produces the transformation of voltage | False |
For an ideal transformer, the power input is equal to the power output | True |
The voltage ratio of a transformer is equal to its turns ratio | True |
If the secondary circuit of a transformer becomes overloaded, the primary circuit will not be affected | False |
A transformer has subtractive polarity when terminal H1 is adjacent to terminal x1 | True |
In a Delta-connected transformer, the phase and line voltages are equal | True |
Instrument transformers provide insulation between the instrument and the high voltage of the power circuit | True |
High voltages are used in transmission lines to reduce the transmission ____ | current |
For a given amount of power delivered, doubling the transmission voltage cuts the electrical loses by ___ | 75% |
A unit substation of a building contains | high-voltage switch gear, low voltage distribution devices, transformer |
Conduit conductor capacity is generally based on a ___ fill ratio | 40% |
The transformer winding coil that delivers power to the load is known as the ___ coil | secondary |
The principle of operation of a transformer is based on ___ induction | mutual |
The efficiency of a transformer is typically in the ___ range | 90% |
The low-voltage windings leads on a single-phase transformer are marked | X1 and X2 |
Three-phase transformers are normally connected in ___ or ___ | Wye Delta |
If the phase-to-neutral voltage is 120 volts in a Wye transformer system the phase-to-phase voltage would be | 208v |
Compared to an equivalent traditional transformer the autotransformer is | lower in cost, smaller in size, lower in weight |
The secondary winding of a current transformer is designed to produce a standard current of | 5A |
Current transformers are used to | supply a small amount of current that is proportional to the main current |