Ques. Why is such modification desirable?
Ans. Because, the additional cost of a series transformer is small in comparison with the cost of building a dial with a large current carrying capacity, and the cost of bringing out a number of heavy leads from a small transformer.
Fig. 2,436.—Diagram of connections for Westinghouse 11 point dial, series transformer and auto-transformer. The auto-transformer has a number of taps connected across the line, the series transformer is placed in series with one side of the line, and connected to a dial, as shown.
Ques. How are dial regulators modified for high voltage?
Ans. Standard dials may be used with series and shunt transformers similar to the method used for heavy current circuits.
Ques. Describe the connections.
Ans. The primary of the shunt transformer is connected across the line and the secondary has a number of taps which are connected to contacts on the dial. The primary of the series transformer is connected in series with the line and two leads from the secondary winding are connected to the dial.
The connections are similar to those shown in fig. 2,437, except that shunt transformers are used instead of auto-transformers.