PORTABLE GENERATOR

Date: 2015-10-07; view: 832.

Answers to all the questions.

Read the text to check as many of the answers as you can. You will not find complete

Diagram and your own knowledge of engineering.

Study the diagram below of a portable generator. Answer these questions using the

1) What are its main parts?

2) What does the engine run on?

3) What are the four strokes called?

4) What is the function of a crankshaft?

5) What do both stator and rotor have?

6) What is the difference between stator and rotor?

Fig. 1

Although most electricity comes from power stations, power can also be generated by far smaller means. Nowadays, electricity generators can be small enough to hold in the hand.

Portable generators are made up of two main parts: an engine, which powers the equipment, and an alternator, which converts motion into electricity.

The engine shown (Fig.1) runs on petrol. It is started by pulling a cord. This creates a spark inside which ignites a fuel mixture. In a typical four-stroke engine, when the piston descends, the air inlet valve opens and a mixture of air and petrol is sucked in through a carburetor. The valve closes, the piston rises on the compressor stroke and a spark within the upper chamber ignites the mixture. This mini-explosion pushes the piston back down, and as it rises again the fumes formed by the ignition are forced out through the exhaust valve. This cycle is repeated many times per second. The moving piston makes the crankshaft rotate at great speed.

The crankshaft extends directly to an alternator, which consists of two main sets of windings – coils of insulated copper wire wound closely around an iron core. One set, called stator windings, is in a fixed position and shaped like a broad ring. The other set, the armature windings, is wound on the rotor which is fixed to the rotating crankshaft. The motor makes about 3,000 revolutions per minute.

The rotor is magnetized and it spins round, electricity is generated in the stator windings through the process of electromagnetic induction. The electric current is fed to the output terminals or sockets.

This type of generator can produce a 700 watt output, enough to operate lights, television, and some domestic appliances. Larger versions provide emergency power to hospitals and factories.