Bob Pelikan

The third and last article in the series on VFDs.

:Last month, we began a discussion on variable-frequency drives ..."

"At various times in our careers, we have to make equipment purchases to grow our business or due to changes in the business environment."

Any time you have a high-flow velocity, particularly in a long pipe run, and there is a sudden change in velocity, water hammer can occur.

For a number of reasons, it may be desirable to start a pump motor slowly, using one of the following soft-start techniques.

Exploring answers to the question, "Why do pump motors fail?". 

Last month, we talked about full voltage-start pump control panels. This month, we will cover the other two main components in a standard panel – the contactor or starter, and overload-protection devices -- as well as single-phase and current-unbalance protection offered by panels.

A three-phase pump control panel is the interface between the incoming three-phase power and the pump.

Phase converters come in various shapes and sizes, costing from a few hundred dollars to many thousands, depending on the horsepower rating and type. The phase converter will artificially generate the third leg of a three-phase system from the two leads of a single-phase system.

The last two articles in this series on electricity focused on single-phase pumped water systems. This article will be the first of several on three-phase systems.