Mains Voltage Compensation

MAIN VOLTAGE COMPANSATION

• Objectives
• Describe main voltage compensation
• Explain the factors that lead to main voltage fluctuation
• Name the components used in main voltage compensation

Explain the methods through which main voltage compensation is achieved

MAIN VOLTAGE COMPANSATION……

• Describe:
• The manually adjusted mains voltage compensator
• Automatic mains voltage compensator.
• Describe the main voltage compensation under the headings:
• Manual mains voltage compensation

Automatic mains voltage compensation

MAIN VOLTAGE COMPANSATION……

Describe the effects on the radiograph following the change in compensation devices under the following headings:

• Tube kilo voltage
• Tube current
• The supply of the filament transformer

Other components of the x ray set timer, monitors, and relays.

MAIN VOLTAGE COMPANSATION

The changes that occur in the mains voltage are caused by:

Slow changes over a period of time due to differences in demand on the supply at various periods in a day.

Rapid changes because some equipment on the line draws a heavy current for short interval.

The fall in the main voltage caused by x ray set itself drawing current for radiographic exposure.

MAIN VOLTAGE COMPANSATION …

The main voltage compensator can not prevent the main voltage changes (above) from taking place.

What it can do is to maintain voltage output from the autotransformer of the x ray unit.

MAIN VOLTAGE COMPANSATION …

This may be manually or automatically adjusted. It acts to maintain a constant volts per turn ration on the autotransformer of the x ray set so that the voltage out put of the autotransformer is not changed by alteration in the input voltage.

It compensates for slow voltage changes occurring outside the x ray exposure

Manually adjusted mains voltage compensator

• Consist of tappings on the autotransformer at one end of the winding.

The tappings can be on either primary side or on the secondary side.

There is also a line voltage compensator meter which is connected across a fixed number of tappings of the autotransformer. It is main function is to indicate any change in the main voltage supply.

Mains Voltage Compensation

For any change in main voltage supply, the main voltage compensator is manually adjusted by the radiographer whether to increase or decrease the number of turns.

( towards A or towards C)

Automatic adjusted mains voltage compensator

This type of compensator has an adjustor with special contactor called a sledge which is driven by an electric motor to obtain a constantly balanced output voltage from the autotransformer.

LINE DROP COMPENSATOR.

This is a special transformer in series with the autotransformer.

It functions to provide a voltage to superimpose on the line voltage in such a way that the extra voltage is matched to the fall in the line voltage which occurs when the load current flows against mains resistance. This compensator compensates only for the mains drop caused by the x ray set itself