I received many comments on my four-part series on AC Power, and most of them were very positive. Several readers, however, thought they were too elementary. I
reminded them that the title of my column is “Pump Ed101” not 201 or 301, and its purpose is to introduce people to new and unfamiliar topics. Why do I use this approach?
Topic Sponsor
Top Motors Articles
The pump industry is the largest purchaser of electric motors in the United States. According to the U.S. Department of Energy (DOE), electric motors consume more 50 percent of all electrical energy in the United States and more than 85 percent of industrial production electrical energy. Electric motors account for roughly $85 out of every $100 of a manufacturing/process plant's electrical bill.
Mechanically generated sparks, electrostatic discharge and high surface temperatures are all potential ignition sources in explosive atmospheres. Flexible couplings play a significant role in creating and/or eliminating these explosion hazards. Consequently, the European ATEX directive applies to couplings, and for good reason.
Following the development of variable frequency converter drives during the 1990s, totally enclosed fan-cooled (TEFC) AC induction motors became viable options for replacing DC motors in pumping applications. The torque and speed characteristics of these motors are a close match to those required for centrifugal pumps.
Because operational costs ride on efficiency determinations, accurate measurements of losses occurring within the motor are paramount. The reliability of efficiency data is key to any energy-savings plan, and knowing the meaning behind the rating can make or break a smart purchasing decision.
Aligning an electric motor coupled to a large air blower required multiple measurements.
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.
Water and wastewater systems in the United States use a tremendous amount of power. The EPA estimates that these systems use 50 trillion watt-hours annually at a cost of $4 billion. Combined with electric rate increases upward of 20 percent in a single year, water and wastewater system operators are left with an enormous strain on their budget.
Bigger Is Better-Or At Least It Used To Be
Owing partly to tradition, the shafts of electric motors are often larger than those of the equipment they drive. Engineers were very conservative a century ago when electric motors first came into widespread industrial use, so they typically designed in a sizable margin of error. Today's engineers haven't changed much in this respect. For example, standard NEMA frame dimensions, which have been revised only once since 1950, still specify much larger shaft sizes than commonly accepted principles of mechanical engineering would require.
Latest Motors Articles
Electric motors have had a huge impact on the pump industry.
Improved motor starters help Fabri-Kal achieve its green vision.
Mechanical resonance occurs when an external source amplifies the vibration level of a mass or structure at its natural frequency. For a rotating mass like a motor or a pump, this occurs at the critical speed(s). Electrical resonance amplifies the magnitude of voltage or current, or both.
This month we will quickly look at the load types that comprise a typical AC circuit.
Last month, we ended with a discussion of the relationship between peak and RMS (or effective) voltage. We found that the RMS voltage will always be 0.707 that of peak voltage, and peak voltage will always be 1.414 that of RMS voltage. This relationship holds true regardless of the sine wave frequency. But, as frequency changes, the total voltage applied to a circuit per cycle can differ substantially. To visualize this difference, we will need to introduce another unit of measure-volts per hertz.
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 depth study at the end of this article.
Improvements in performance and energy reduction can be achieved with smart drives and system optimization.
The industrial motor world has a new specification available for defining the requirements of general purpose, severe duty motors in the 250- to 3,000-hp range.
The pump industry is the largest purchaser of electric motors in the United States. According to the U.S. Department of Energy (DOE), electric motors consume more 50 percent of all electrical energy in the United States and more than 85 percent of industrial production electrical energy. Electric motors account for roughly $85 out of every $100 of a manufacturing/process plant's electrical bill.
A large wastewater processing plant experienced continual problems with its influent raw wastewater pumps for several years. These pumps are rated at 70,000-gpm, 24-ft head and driven by 500-hp, 4000-V, 225-rpm Westinghouse brushless synchronous motors, 57.5-amps steady state rated current.
Industry News
Columns and Blogs
The performance of a centrifugal pump with a trimmed impeller will follow the affinity laws as long as that trim is relatively small.
Standards for repair will begin with a standard for vertical turbine pumps.The pump industry is undergoing renewed interest in the technical aspects and quality of repairs.
Charlie Jackson was unaware of any centrifugal pump manufacturer that knew how to calculate hydraulic axial thrust produced within liquid ends of their pumps.
