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AIM OF THE UNIT:-to understand load sharing

3 Make up questions to the text. 4 Find the sentences with the new words in the text. Give the Kazakh or Russian

equivalents of the words.

5 Write sentences with the new vocabulary. 6 Make up exercises as in the UNIT 2page 210(Exercises for better remembering the topic).7 Speak on the topic. Given schemes will help you to remember and understand

the topic.

When a load is placed on an ac busbar, the nature of the load will determine the power factor of the system. Any load current, whether leading or lagging, can be thought of as having two components:-

One in phase with the voltage.

The component in phase with the voltage is termed the real load component and the quadrature component is termed the reactive load component.

If one generator is supplying a given load it has to supply both of these components in their entirety and no question of load sharing arises. When two (or more) generators are supplying the same load they must share the available real and reactive loads equally. To do this the actual currents supplied by each machine must be identical and their power factors must also be identical.

No. 1 generator is supplying more than its fair share of the real load and yet equal sharing of reactive loading is maintained. Under these conditions, the actual current supplied by No.1 is greater than that supplied by No.2 and No.1’s power factor has moved towards unity whilst No. 2's power factor has decreased. No.1 is supplying more than its fair share of reactive load and yet equal sharing of real load is maintained. Again, the actual current supplied by No. 1 is greater than that supplied by No.2, but now No.1’s power factor has decreased whilst No. 2's has moved towards unity.

The condition can arisein which No. I supplies more than its fair share of both real and reactive loading and the power factors of the two machines can remain identical. Under this condition, however, the actual current supplied by No.1 will be vastly greater than that supplied by No.2.

Actual currents may be equal yet power factors could be different. It will be evident, therefore, that it is necessary to provide two load sharing devices:-