2-1 workbook

Explain how the thermo-couple meter works.

Current heats both hot wire and thermo couple junction. D.C. voltage produced causing meter to indicate current flow.

What is another word used to describe an A.C. generator?

Alternator

Which direction should the light sensitive element face, and why?

North- bright sunlight will damage the cell

Why is the core laminated?

To eddy current loses

Name the three basic parts of a transformer.

a.) Primary windings b.) Secondary windings c.) Iron core

Why are filament lamps so widely used?

a.) lamp size b.) cost c.) color quality

Of what does the plunger-type meter movement consist?

A movable soft iron core within a fixed coil.

List two reasons A.C. is more popular than D.C.

A.C. can do anything D.C. can and it's easier as well as cheaper to transmit.

Alternating current generators are sometimes called _______.

Alternations

The _______ ______ meter movement operates similarly to the radialvane meter movement.

Conservative vane

Name two parties responsible for inspection and test of rubber goods

Lineman and safety services.

In transmission of A.C. power, the best way to reduce the power loss is to (raise/lower) the current.

Lower

A generator converts ______ energy to _______ energy.

Mechanical; electrical

What type transformer is used to feed the expressway street lights?

240/480 single phase

Line hoses are manufactured in ______ lengths, with inside diameter measurements that vary from ____ to ____.

Various; 1" ; 1.5"

What is the total voltage drop for a parallel circuit?

The entire source voltage.

Define the term "induced voltage" as it applies to transformer action.

The magnetic field that induces voltages from primary windings to secondary.

In actuality what is the normal range of a power factor _____ to _____.

.70; 1.00 lagging

Which is used at the Division?

Both

What are two things that the voltage drop depends upon?

a) current b) resistance

Rubber gloves should be thoroughly cleaned, inspected and tested by _______ personnel regularly.

Competent

A circuit has to provide a ______ path from the negative terminal of the power source to the positive terminal in order for current to flow.

Complete

Transformer oil serves what purpose?

Cools and insulates

The power is defined as the ratio of the actual power to the product of volts times amperes. This product of volts time amperes is commonly referred to as _____ power.

Apparent

The plunger-type moving iron meter operates on the principle known as _______.

Attractive

On D.C. generators the current is taken from the generator by means of _____ which make contact with the _______.

Brushes; commutator

On A.C. generators the current is taken from the generator by means of _______ which make contact with ______ ______.

Brushes; slip rings

Rubber insulating sleeves must be treated with ______ and ______ regularly by the lineman.

Care; inspected

The number of cycles generated in one second with A.C. is called the _______.

Frequency

What is the time clock control and how does it operate?

Switch actuates by a relay which opens & closes its contacts in ascendence with the hours of sunrise & sunset.

Since all generators produce A.C. current, what determines whether the voltage is A.C. or D.C. on the line?

The way the end of the loops are connected.

In what ways are alternating current generators different from direct current generators?

They have slip rings to produce a current.

What is the basic purpose of leather protectors over rubber gloves?

To prevent damage to the glove

About 90% of all electric power consumed throughout the world is A.C. T or F

True

Current travels at 186,000 miles per second. T or F

True

It's important that you know how to connect a meter into a circuit to make a particular measurement. T or F

True

Rubber gloves should always be given an air test by the lineman or cableman each day. T or F

True

Since current flows from the negative terminal of a power source to the positive terminal, for A.C. current, the polarity of the power source must alternate. T or F

True

The drop across the load is opposite to that of the source. (T or F)

True

What is the largest value the power factor can be?

Unity

When an alternating voltage and the current which it causes are in phase, the power factor is _____.

Unity

What prevents the element in a filament bulb from burning up?

Vacuum

A current meter can be calibrated in units of ______ or ______ because all three are related by Ohms Law.

Voltage; Resistance

Write the equation for Power equal to Voltage multiplied by the current with a power factor equal to one.

Watts = ET•I

Explain the moving-iron movement.

When current flows through the coil both bars are magnetized with the same polarity and repel each other causing them to move apart.

During the generation cycle, at what point is there no current flow in the line?

When no flux lines are being cut.

Explain how the moving coil meter movement works.

When the coil is energized a magnetic field is set up within the coil. The poles of the magnet and coil oppose each other causing the coil to rotate on its pivot.

At what point in the generation cycle is there maximum current flow?

When the max number of flux lines are being cut.

Is it possible to use different types of street lights on the same circuit?

Yes

A transformer has a primary voltage of 7,200 volts( a primary Current of 5 amps and a secondary voltage of 240 volts. a.) What is the turns ratio? b.) What is the secondary current? c.) What size transformer would be needed to carry this load?

a.) 30 to 1 b.) 5 • 50/1 = 150 c.) 37.5

Why is good voltage regulation important in a multiple street lighting system?

a.) Low voltage- reduced light b.) high voltage- short lamp life

Name 5 types of information given on the transformer nameplate.

a.) size b.) voltage c.) polarity d.) weight e.) serial number

What is the purpose of the iron core in a transformer?

A path for the flux lines.

Will adding resistance or load in parallel increase the voltage drop in the circuit.

No

What is the purpose of a time delay relay?

Cools lamps before restart

What is the voltage rating on expressway underpass lights?

120 volts

How many degrees are there in 3/4 of a circle?

2,700

What advantage do mercury vapor lamps have over filament lamps?

2-3 times more light

What is the voltage rating on the mercury vapor lamps used on the expressway?

220 volts

In a transformer with a turns ratio of 30 to 1 and a secondary voltage of 240 volts, what is the primary voltage?

240•30=7,200 volts

How many conductors are required to carry away the output of a three phase generator to the transmission line? Explain your answer.

3 (ABC Phase)

Most of the electric power generated in the United States has a frequency of _____ cycles per second.

60

Express the power factor of a loaded induction motor as a percent.

80% lagging

At a primary voltage of 7,200 volts, what size transformer would be needed for a load demand of 600 amps at 480 volts?

P= E•I P= 480•600 P= 288,000 P=288 KVA

____ -type or _____ -type distribution primary insulators can be covered by hoods.

Pin; past

a.) In a "step-down" transformer the _____ coil has the greater number of turns. b.) In a "step-up" transformer the ______ coil has the fewer number of turns.

Primary; Primary

In a "step-down" or distribution transformer the _______ winding has _____ turns that the _____ winding.

Primary; more; secondary

What type must you use if you connect the light to existing secondary?

Relay in head

What does R.C.O.C. mean, and where are they used?

Remote control oil switch; interstate lightning system.

The repulsion-type moving iron meter operates on the principle known as ______.

Repulsion

Odd shaped conductors and equipment can usually be covered best with a _____ ______ ______.

Rubber insulating blanket

What are CDS cells rated at?

1,000 watts

There are two basic types of electro-magnetic current meter movements in use today. Name them.

1. Moving coil type 2. Moving iron type

In an electric circuit, the condition of no resistance and very high currents, is called a ______ ______.

Short circuit

Meters can only measure the amount of _______ flowing through them.

Current

What are three types of lamps are used in our street lighting system?

1.) Incandescent 2.) Mercury Vapor 3.) Sodium Vapor

What three functions does the hood of a luminaire serve?

1.) Provides a mounting for the optical assembly. 2.) Provides means for mounting the socket. 3.) Provides means for mounting the luminaire to the bracket.

What are two functions of a ballast?

1.) Supply voltage to strike the arc under any ambient condition that's encountered in service. 2.) to limit the current to the design ampere rating.

Name the two basic types of photoelectric controls and where each is used.

1.) Tube type- multiple system 2.) Sodium sulfate- relay in head type

Explain how you would test a rubber blanket.

Clean and visually check for cuts and holes.

If a four pole generator were placed with an eight pole generator you would have to _______ the RPM by ____% to maintain the same frequency.

Decrease; 50

How are expressway underpass lights fed?

Dry type 480/120

If the peak voltage is 90 volts, what is the average voltage of this A.C. circuit l?

E AV= 0.637 E AV= 0.637 EPV= 0.637•90=57.3v

Proper application of protective equipment is necessary for linemen to safeguard the work area, that is, to prevent ______ ______ or _____ ______ injuries.

Electrical shock; flash burn

The _________ ______ meter is the one used most often to measure current, voltage, resistance, and power.

Electromagnetic Current

What is luminous flux?

Energy in form of light.

What is the total voltage drop of a series circuit?

Equal to the source voltage.

In a CDS cell, the flow of current through the relay causes the contacts to close and the lamps come on. T or F

False

The current in lightly loaded induction motor lags the voltage by 50%. T or F

False

Explain how alternating current is generated.

It's produced mechanically and converted to electrical energy.

The terms _____ and _____ are used to describe the relative positions in time of two voltages or currents that are out of phase.

Lead; lay

One _____ uniformly distributed over one square foot of surface produced an illumination of one foot candle.

Lumen

What is a lumen?

Luminous flux on a surface are square foot area.

Define candlepower.

Luminous intensity EFA light source.

The amount of current flowing through the wire determines both the strength of the ______ ______ and the amount of _____ produced.

Magnetic field; heat

What are two basic types of street light circuits?

Multiple and parallel

In a transformer how is the primary connected to the secondary?

Mutual induction

What does "turns ratio" mean?

Number of primary turns to secondary turns

How many coils does an auto-transformer have?

One

No current flows in an _____ series circuit, therefore, there are no voltage drops across the loads.

Open