Souces of Power

Author: N.H. Crowhurst

In all our discussions thus far, we have described amplification in terms of tubes and other components that need voltages applied to them to make them work. We have not considered where these voltages come from, but they all need to have the right voltage supplies, whatever they may be.'

Sources of power

In most modern equipment these supplies come from an electrical power company, most of which deliver a voltage of 11? volts at 60 cycles. Other supplies are sometimes used; for example, in aircraft, where the frequency is not 60 cycles, but 400 cycles, and in automobiles, where the supply is not a-c but d-c, at 6 or 12 volts from a battery. We are principally concerned with 117-volt 60-cycle a-c sources. If the supply is a-c of a different frequency, as in aircraft, the details of the design will be altered but the principles will be the same. Where the supply is d-c, as in automobiles, and in a few isolated locations where the power company supplies it at a higher voltage, such as 110 volts, a different kind of power supply circuit is required. The convenience of a-c as a source of supply is that the voltage can easily be stepped up or down by means of a power transformer.

The transformer: the voltage of a source can be stepped up or down easily with a transformer.