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...
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...
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 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...
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...
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...
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...
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...
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...
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...
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...
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...