UNIT 4 VOLTAGE REGULATION

AIM OF THE UNIT:- to understand voltage regulation

TASKS

1 Do your best to answer the brainstorming question. 2 Read the text for general understanding.

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 2 (Master`s degree students individual work with the teacher) page 210 (exercises for better remembering the topic).

7 Speak on the topic. Given schemes will help you to remember and understand

the topic.

8 Find more information about the topic and make up a project work on the topic.

The voltage regulator that is used in our system is a carbon pile voltage regulator. The voltage regulator controls the field F1 of the dc exciter generator therefore reducing the workload on the voltage regulator over large changes of speed and load. On start up, the residual magnetism in the dc exciter will enable the exciter to provide an initial output to the rotating field. The output voltage will build up and be sensed by the sensing transformer in the regulator unit.

The Output of the 'field supply' secondary of this transformer is rectified and fed via the carbon pile to field F1. The output of the 'a.c. control' secondary is rectified and fed to the volts coil of the carbon pile regulator. The carbon pile will gradually decompress to increase the resistance of Field F1 and control the line to line voltage at a nominal 208 V.When the TRU contactor is de-energized the regulator is said to operate in the 'ac sensing' mode. In a frequency wild system all circuits, other than the resistive heating loads, are supplied with dc. It is therefore necessary to provide high power main transformer rectifier units each with an output of 500 A at 28 V. When the TRU contactor is energized it is essential to maintain the busbar at 28 V. To achieve this, the regulator voltage coil is disconnected from the 'ac control' secondary and connected to the busbar. The regulator will now ensure that any change in busbar voltage is sensed and corrected. Current compounding provides a second field F2 with excitation current proportional to the generator load current. The compounding circuit enables small carbon pile regulators to be used with high power output generators. The ratio of the compounding current to the load current is such that the compounding current is always less than the necessary excitation current..