For those of you old enough to remember Lawrence Welk, you’ll notice that the title of this brief column is the final quote from his show’s closing song. I am still a loyal fan of his reruns...
In my last column (Pumps & Systems, October 2014), I explained that a capacitor’s current is totally out of phase with that of a motor’s magnetizing current. This allows the capacitor to store...
I hope that my last column (Pumps & Systems, September 2014) provided a clearer definition of power factor and how it can be calculated. Power factor can also be explained using a vector triangle, but...
Power factor (PF) is an important component of an alternating current (AC) circuit, but understanding its actual effect can be difficult. Why is PF mysterious to many of us? It has to do with the way...
In my July 2014 column, I demonstrated that three-phase voltage variation can significantly affect several alternating current (AC) motor characteristics. If that variation is large, it can also...
In my June column on pump and motor testing, I said that three-phase voltage variation and unbalance can have a significant effect on motor insulation life. Voltage variation is defined as the...
This article is part of our ongoing series on The History of Pumps. During the past few years, I have written articles about scientists who have contributed to our understanding of hydraulics....
Today’s federal requirements dictate the minimum efficiency of an electric motor, but they do not have any impact on the efficiency of a centrifugal pump. A 10-horsepower, 1,800-rpm motor must meet...
This article is part of our ongoing series on the history of pumps. In 2008, I wrote a two-part article on waterhammer and how it can damage pumps and piping systems. It is the result of a change...
In my opinion, the system curve is the single most important component of the pump selection process. After all, the system curve determines the operating point on a pump’s performance curve. Other...
In the February 2010 issue of Pumps & Systems, I discussed my Suction Specific Speed (S) Calculator and its ability to predict the stable range of flow for a particular centrifugal pump. In November...
Breadth of Efficiency
In 2012, I wrote a six-part series on centrifugal pump efficiency. In Part Five, I touched on the importance of the breadth of efficiency and how it can be more useful than the peak best efficiency...
Why Wye? Why Delta?
Last of Three Parts
Why Wye? Why Delta?
Pumps & Systems, July 2013Second of Three PartsThe secondary configurations reviewed in Part One (Pumps & Systems, June 2013) are typical three-phase configurations found in pump applications....
Why Wye? Why Delta?
Why a Wye or Delta connection is required in a three-phase circuit
Motor Horsepower & Torque Versus VFD Frequency
How a Variable Frequency Drive or VFD relates to horsepower and torque.
Three Fictitious Forces & One Real Force
Pumps & Systems, April 2013Two schools of thought exist with regard to centrifugal force. The one I support views it as a false force. The other side believes that it is real. That is the side...
First of Two Parts Branch-line pumping applications abound throughout the pumping industry. These systems consist of a pump (or pumps) discharging into a single line that feeds a network of...
Last year, a Pumps & Systems reader asked about matching variable frequency drives (VFDs) and motors. “I have a spare pump in my warehouse that requires 15 horsepower (HP) at best efficiency...
Memorization and learning are two different things. As I look back on my own education—formal and real life—most of the facts and figures that I memorized are long gone. Even today, routine...
"Testing Centrifugal Pumps in the Field,” Pumps & Systems, February 2011, featured an Excel spreadsheet designed to simplify the field test procedure. The equation for total dynamic head (TDH)...
The Bernoulli Principle
Read Part OneRead History of Pumps seriesThe Bernoulli Principle explains the flow of fluids and was one of the earliest examples of conservation of energy. It states that during steady flow, the...
The Life and Work of Daniel Bernoulli
Editor's Note: This is the first article in a two-part series on Daniel Bernoulli. The series is part of a larger ongoing series on the history of pumps.Have you ever noticed that the pressure...
Centrifugal Pump Efficiency—When Is Efficiency Important?
Editor's Note: This is the sixth in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.The power required by a pump is directly proportional to both the...
Centrifugal Pump Efficiency — Curve Shape & Breadth of Efficiency
Editor's Note: This is the fifth in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.Curve ShapeIn Part 2, I showed the effect of specific speed (Ns) on...
Centrifugal Pump Efficiency—Preservation of Efficiency
Editor's Note: This is the fourth in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.The performance of a centrifugal pump with a trimmed impeller will...