A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification. Here is what Wikipedia tells us about “rectifiers”:

“Physically, rectifiers take a number of forms, including vacuum tube diodes, mercury-arc valves, copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled rectifiers and other silicon-based semiconductor switches. Rectifiers have many uses, but are often found serving as components of DC power supplies and high-voltage DC power transmission systems. Rectification may serve in roles other than to generate direct current for use as a source of power. For example, detectors of radio signals also serve as rectifiers.”

Depending on how old you are, you may or may not be aware that once upon a time all of our TV’s, radios had no transistors in them but instead use what were know as vacuum tubes (see image above) to make them work.  One of the key uses for the “diode” variants of these tubes was as a rectifier. 

Why are we posting a TRHA News item about rectifiers? 

Because among the artefacts in our museum is a most fascinating example of a rectifier used in the Roundhouse likely in the 1950’s or earlier. The challenge in the Roundhouse was to provide high amperage power supplies to charge the massive batteries found in both passenger cars and diesel locomotives.  The solution was a massive power supply which measures about 3 feet by 3 feet and stood about 7 feet high. 

If you visit our museum today, we now have this unit on display.  The most fascinating part of the unit is a massive vacuum tube rectifier which as about two feet high and two feet wide (see image below).  We suspect that the power supply was capable of producing up to 250 amperes at 250 volts as the meters (see images below) are rated that high.  If that is the case, the power supply can produce 62,500 watts. Impressive!

Today, rectifiers are all solid state devices and you could likely hold one of this power rating in one hand.

Click on each image for a closer look!