Columns and Blogs

Last month, we studied the properties and effects of resistive, inductive and capacitive loads in an AC circuit.

As a follow up on my AC Motors series, I thought it would be a good idea to provide a short overview of work, power and torque as it applies to the AC motor.

When selecting a pump for variable speed operation, a number of conditions must be evaluated.

Starting can have a significant effect on the life of the winding insulation of an AC motor.

I received many comments and suggestions on proper installation practices, following my article “Grouting: Pumps and Telephone Poles,” Pumps & Systems, July 2010).

Energy efficiency and reduced consumption are important issues in the pump and motor marketplace.

Using pump system analysis, from simple to the complex

The radial forces that form about the periphery of a single volute pump's impeller are proportional to total pump head, impeller diameter and vane width. They are seldom balanced, but they reach their lowest intensity between 80 and 100 percent of BEP flow.

About 900 years before Newton formulated his universal gravitational theory, the Greek philosopher Aristotle espoused something different.

In Pumps & Systems January 2007, I wrote an article about cavitation and how a collapsing water vapor bubble can damage an impeller. Since then, I have received a number of requests to address Net Positive Suction Head (NPSH) and its relationship to cavitation. Here it is in a very simple, Pump Ed 101 perspective.

A number of choices are available when connecting pumps, fans and other rotating equipment to an electric motor. There are numerous mechanical and fluid coupling designs and, in some cases, a belt drive option is available.

The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result of inefficiency and the need to dissipate heat.

Dr. Lev Nelik answers pump user questions.

This is a follow-up to my column on predicting centrifugal pump performance (Pump & Systems, May 2011), and offers equations that will enable the engineer to perform a partial analysis of the impeller eye.

The frame sizes (physical dimensions) of AC motors have changed substantially through the years. Originally, they were considerably larger than those in use today. This increased size was the result of inefficiency and the need to dissipate heat.

Efficiency degradation in pumps can be related to three areas.

Based on several of my previous Pumps & Systems articles, you probably know that I have major concerns about the off best efficiency point (BEP) operation of wastewater pumps.

When the motor amps are kicking a unit offline, the first question is whether the motor or the pump is the problem.

One of the major impacts on motor life is common sense—or maybe the lack thereof!

While scheduled downtime is different from unscheduled, both can take away from a company.

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