Faults of Motors and Ways of Their Repair

Energy Resources of Today

People are energy-rich today. Solar energy is considered to be a poten­tially limitless source of clean energy. The waters of the world contain po­tential fuel - in the form of a special isotope of hydrogen - deuterium. It is sufficient to power fusion reactors for thousands of years.

1. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

to repair	1преэ]	ремонтировать
brush	[ЬглЛ	щетка
gap		зазор, люфт
spark		искра
speed		скорость
noise	[nDlz]	шум
slow		медленный
excessive	[ik'sesiv]	избыточный
check		проверка
to adjust		регулировать, подгонять

2. Read the words and put down their Russian equivalents:

['komju:teit3] commutator ________________________

stator rotor contact to contact process

t'steitaj

['routaj ['kontaekt] [kan'taekt] ['prouses]

to check

check spark brush

3. Put down the verbs corresponding to the given nouns and translate them:

проверять

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repair slow (adj)

4. Put down the Russian equivalents of these word combinations. Trans­
late them back into English (orally).

air gap __________________________________________________

brush sparks zzziizzzzzzzzzzzzzizzzi^zmm

slow speed___________________________________

excessive speed_________________________________

safety devices __________________________________

5. Answer these questions:

1. What do motors' faults result from?

2. Are there any faults that can be ignored?

3. What makes motors' service life shorter?

4. What does voltage supply stop result in?

5. What processes show the (dis)advantages of devices?

6. Are the words: spark, short, slow, brush, fault, load, test nouns? Are
they verbs? Translate the sentences into Russian:

1. New motors are given a no-load and under a load tests.

2. When the motor is tested it should produce no abnormal noise.

3. In case this noise appears the motor must be disconnected.

4. This generator must be checked; one should give it a test.

5. The motor's brushes seem to be sparking. Can you see the sparks?

6. The windings of the coil are shorted. I have detected a short in the windings.

7. The armature rotates slowly; let's check it up!

8. The speed of rotation is too excessive; it must be slowed down.

9. In case the rotor brushes against the stator, the motor operates slowly. The faulty brushes should be replaced.

Motors may have different faults. A faulty motor does not start, or, when it is started, it operates at an excessive speed.

Its brushes may spark and its windings and the commutator may be overheated and burnt. Besides, a motor may produce an abnormal noise, etc. All these and other faults should be detected and repaired.

In case the motor does not start it may have different faults (see the ta­ble):

Table

Possible causes of faults	Ways of repair
1. Fuses are faulty.	1. Replace the fuses.
2. Motor is overloaded.	2. Reduce motor load.
3. Circuit in armature winding has an open.	3. Repair the armature winding.
In case the motor, when started, stops:
1. Rheostat is shorted.	1. Check the rheostat and re­pair it.
2. Rheostat switches from one position to another.	2. Slow down operation of rheostat handle.
Brushes may spark in case:
1. Motor is overloaded.	1. Reduce the load and re­move overload.
2. Brushes are in poor condition.	2. Replace the brushes.
3. Pressure is low.	3. Adjust the pressure.
4. Pressure is excessive.	4. Adjust the pressure.
In case the armature winding is overheated:
1. Motor is overloaded.	1. Remove the overload.
2. Ventilation fails to operate properly.	2. Check for slowing down the speed of the motor.
In case of abnormal motor speed:
1. Motor is overloaded.	1. Reduce the load.
2. Rotor circuit has poor contact.	2. Repair the shorting mechanism.
In case rotor brushes against stator:
Rotor brushes against stator.	Adjust air gap.

7. Complete the sentences using the correct variant:

1. A motor with a fault a) operates normally.

b) operates poorly.

2. Motor brushes spark in case a) they are in normal conditions.

b) they are in poor conditions.

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3. Burnt commutator should be

a) replaced.

b) repaired.

  4. Brushes may spark in case 5. Air gap is adjusted in case

a) pressure is low.

b) pressure is excessive.

a) the rotor brushes against the stator.

b) the stator brushes against the rotor.

8. Answer these questions:

1. When does a motor operate poorly?

2. What should be done in case the motor is overloaded?

3. What should be done in case the fuses are faulty?

4. What should be done in case the rheostat is shorted?

5. What should be done in case the brushes spark?

6. What should be done in case the pressure is low?

7. What should be done in case the ventilation does not operate?

8. What should be done in case the rotor brushes against stator?

9. Say a few words about your electrical engineering laboratory. Are there any faulty devices in it? Have a talk with your groupmate about the faults and the ways to repair them.

10. You know that all electrical devices and installations are constructed of a certain number of components. To these components belong elec­tric power sources, wires, cables, buses, switches, fuses, resistors, rheo- j stats, capacitors, transformers, motors and others.

Let us have a talk about these components. Speak with your group-] mates about their types, their use, operation, possible faults and ways of their repair. Use the table below:

Symbols

Circuit components

E

Electric energy source

-C©J-

D.c. generator

—^{мр—

D.c. motor

nh

Chemical power source (primary or storage cell)

Circuit components	Symbols
Electric lamp	®
Electric connection, removable and permanent	• О 0
Switches, single- and double-pole switches	4 «
Fuse
Load, resistor	r
Safety earthing system	i
Rheostat, or variable resistor	-&- h5-
Transformer, air-core T,	DE
iron-core T	ЭЕ
Capacitor, fixed C, variable С	$4

11. Draw schemes of circuits and devices constructed from these compo­nents. Have a talk with your groupmates about them:

1. Connect four resistors, two voltage sources and a switch in series. Speak about the construction and the operation of the circuit.

2. Connect several resistors and cells in series-parallel. Suppose that one of the resistors gets open; what does it result in? Suppose that a whole set gets open. What does it result in?

3. Measure the value of current (voltage, power, resistance) in the circuit. Use proper meters. Speak about the way you connect the meters to the circuit.

4. Take the proper components and construct an earthing protection sys­tem. Draw its scheme. Speak about its operation.

5. Draw a scheme of a thermal relay. What components are necessary for it?

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6. Draw a scheme of an overhead transmission line. Speak about its op­eration. What are its possible faults?

7. Draw a scheme of a substation. Speak about its operation and about its possible faults. What are the ways of their repair?

1. a) Cover the right column and read the English words. Translate them into Russian and check your translation.

b) Cover the left column and translate the Russian words back into English.

to achieve to belong (to) to feed to determine to relate predominant graph national economy

[э'флг]

достигать

принадлежать, относиться (к)

[dita:mm]

снабжать, питать

определять

относиться (к), быть связанным (с)
[pn'dommant] преобладающий
[gra:f] кривая, график

народное хозяйство

2. Read the words and put down their Russian equivalents. Then trans­late them back into English (orally).

characteristic municipal -to electrify -hydro -period -

[.kaenkta'nstik]

[mju:'nisipl]

[I'lektnfai]

[[tiaidrou]

['piariad]

3. Distribute the words below into three columns:

actionprocessdoer

utilizer, protect, distribution, utilize, protection, distributor, consumption,! consume, utilization, consumer

4. Put down the Russian equivalents of these word combinations. Trans­
late them back into English (orally).

a. load graph_______________________________________

lighting load_______________________________________ J

power load________________________________________.1

b. power utilizing devices parallelly operating plants enterprises utilizing power

5. Complete the sentences translating the words in brackets:

1. Water-turbine (заводы) are called hydroturbines.

2. Load graph (определяет) the operating load (условия).

3. Economical (потребление) of electric power (достигается) by inter­connected operation of power plants.

Electric Power Consumers and Power Systems

An electric power consumer is an enterprise utilizing electric power. Its operating characteristics vary during the hours of day, days and nights, days of week and seasons.

All electric power consumers are divided into groups with common load characteristics. To the first group belong municipal consumers with a predominant lighting load: dwelling houses, hospitals, theatres, street lighting systems, mines, etc.

To the second group belong industrial consumers with a predomi­nant power load (electric motors): industrial plants, mines, etc.

To the third group belongs transport, for example, electrified rail­ways. The fourth consists of agricultural consumers, for example, elec-trotractors.

The operating load conditions of each group are determined by the load graph. The load graph shows the consumption of power during dif­ferent periods of day, month, and year. On the load graph the time of the maximum loads and minimum loads is given.

Large industrial areas with cities are supplied from electric networks fed by electric power plants. These plants are interconnected for opera­tion in parallel and located in different parts of the given area. They may include some large thermal and hydroelectric power plants.

The sum total of the electric power plants, the networks that inter­connect them and the power utilizing devices of the consumers, is called a power system. All the components of a power system are inter­related by the common processes of protection, distribution, and con­sumption of both electric and heat power.

In a power system, all the parallelly operating plants carry the total bad of all the consumers supplied by the given system.

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