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...
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...
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...
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 will provide a reference to a more in...
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 will provide a reference to a more in...
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...
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...
AC Motors Part 5: AC Motor Life
One of the major impacts on motor life is common sense—or maybe the lack thereof!It always amazes me how many open drip proof (ODP) motors are used in agricultural irrigation applications where...
AC Power (Part Four): Transformers
Last of four partsLast month, we studied the properties and effects of resistive, inductive and capacitive loads in an AC circuit. This month, we will take self induction a step further and apply it...
AC Power (Part Three): AC Circuit Loads
AC Circuit LoadsLast month we discussed the relationship between voltage and frequency and tried to make that somewhat complex three phase sine wave a bit more understandable. This month we will...
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...
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...
Calculating Energy Savings and Payback
Energy efficiency and reduced consumption are important issues in the pump and motor marketplace. Over the long term, electricity costs will continue to increase regardless of our actions. This will...
Calculating Pump Starts and Cycle Time
Starting can have a significant effect on the life of the winding insulation of an AC motor. For this reason, motor manufacturers often limit the number of starts per hour and may also require a...
Calculating Radial Thrust
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...
Centrifugal Farce & Affinity- It's All About Velocity
Why do those three affinity laws do such a good job of predicting the performance of a centrifugal pump when its rotational speed or impeller diameter is changed? Well, it turns out that they are not...
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...
Editor's Note: This is the second in a six-part series on centrifugal pump efficiency. For other articles in this series, click here. Early centrifugal pump design was heavily influenced by turbine...
Editor's Note: This is the first in a six-part series on centrifugal pump efficiency. For other articles in this series, click here.In this multi-part series, we will investigate several aspects of...
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...
About 900 years before Newton formulated his universal gravitational theory, the Greek philosopher Aristotle espoused something different. He believed that all things had a natural place in the...
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...
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....
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...
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...
Motor Horsepower & Torque Versus VFD Frequency
My January 2013 Pumps & Systems’ column focused on the reduction in motor horsepower (HP) as frequency is reduced by a variable frequency drive (VFD). I had several requests to revisit this...
Net Positive Suction Head: NPSHR and NPSHA
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...