Columns and Blogs

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.

Strengthening of bent shafts is a tricky and controversial process.

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.

These days, the importance of a fresh water supply and safely-treated wastewater return to the river cannot be overemphasized. No matter how hard we try, we are still a long way from the most efficient, economic and reliable ways to ensure that our cities are properly equipped and ready for the clean water challenge.

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.

How viscosity affects centrifugal pumps

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.

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

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.

There are several ways to control two identical, parallel pumps operating under variable frequency control in pumping applications.

This month we will quickly look at the load types that comprise a typical 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.

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.

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

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

Using pump system analysis, from simple to the complex

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

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

Dr. Lev Nelik answers pump user questions.

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