History of the electric machines

The Manchester Mechanics Institution was founded in 1824 and developed its international reputation as a centre of technological education throughout the nineteenth century. Records show that, at the turn of the century, the study of rotating electrical machines constituted a major part of the curriculum in electrical engineering. This emphasis has naturally diminished with time but the interest and activity in electrical machines within the Institute has persisted until the present day. This is contrary to trends in the US and elsewhere and is a phenomenon which is common to a small number of centres of enthusiasm in British Universities. To set this into historical perspective, it is recalled that Faraday conducted his experiments on electromagnetism around 1831.

In the third year extended courses on the technical applications of electricity to lighting, traction, power transmission, and electro-chemistry are given. A special feature is made of the practical work in the laboratories, to which the greater part of the student's time is devoted, and a careful experimental study is made of the leading types of dynamos, motors, transformers, and electrical instruments and appliances. In the design classes, original designs for dynamos, motors, and electrical appliances are carried out.

2. Listen to the text “History of the electric machines” and try to understand it.

3. True or false statements.

1. The Manchester Mechanics Institution was founded in 1924.

2. The Institution developed its international reputation as a centre of technological education throughout the nineteenth century.

3. The study of rotating electrical machines is a major part of the curriculum in electrical engineering.

4. The course for the third year comprises the measurement of resistance and insulation testing.

4. Listen to the text once again and answer the following questions:

1. When was the Manchester Mechanics Institution founded?

2. When did the institution develop its international reputation?

3. What was a major part of the curriculum in electrical engineering?

4. When did students study leading types of dynamos, motors, transformers?

5. The Institution indicated the emphasis on practical work, didn’t it?

V Communicative skills.

What is your point of viev about the future of machines?

Unit 14 Electric Machines Motors and generators

1. Pre-reading tasks.

1. you will read a text about the principal kinds of the direct current motors. What motors do you know?

2. Read and memorise the following words and word-combinations in their specialized meanings.

1. loop – шлейф

2. field coil – котушка індуктора

3. to revolve – обертати, повертати

4. squirrel cage – коротко-замкнутий

5. circuit – схема, контур

6. compound – змішаний

7. windings – обмотка

8. armature – якір, арматура

9. direct current – постійний струм

10. alternating current – перемінний струм

2. Read and translate into Ukrainian the following text. Motors Direct-current motors (a)

A machine that converts electrical energy into mechanical energy is called a motor. The functions of a dc generator and a dc motor are interchangeable in that a generator may be ope-rated as a motor, and vice versa. Structurally, the two machines are identical. The motor, like the generator, consists of an electromagnet, an armature, and a commutator witch its brushes.

It must be remembered that any current flowing in a loop or coil of wire produces a magnetic field. This is exactly what happens in the armature of this motor.

Direct-current motors are classified as: (1) series-wound; (2) shunt-wound; (3) compound-wound; and (4) permanent-magnet (PM). In series-wound motors, the field coils and armature are connected in series, and the entire current flows through the field coils. In the shunt-wound motor, the field coils and the armature are connected in shunt; therefore, the field current is only a small portion of the total or line current. The compound­-wound motor incorporates both the series-wound and the shunt-­wound windings. A PM motor substitutes permanent magnets for the field coils. The armature, brushes, and commutator are the me as for other DC motors.

In construction, all dc motors have a stationary field member (frame or yoke) and a rotating armature member. The frame, which is made of cast or fabricated steel, serves as a support for the motor and is a part of the magnetic circuit connecting the field poles and the commutating poles. The armature is made of wire-wound coils embedded in parallel slots on the surface of the armature core.