This month we will quickly look at the load types that comprise a typical AC circuit.
Topic Sponsor
Top Motors Articles
It is impossible to balance line-to-line voltages perfectly in a three-phase circuit. In fact, line voltages typically differ by a few volts or more, but a difference that exceeds 1 percent can lead to serious trouble on the plant floor. To maintain peak energy efficiency and thwart premature failure of three-phase motors, install adequate protective devices and periodically check for voltage unbalance at the motor terminals.
With highly reliable electrical systems, protective relays may be called upon to operate very infrequently. However, the effects of faults and abnormal conditions can be severe and protective relay systems must be designed carefully to protect against the worst possible fault conditions.
Why integrating vibration monitors with process controls provides fast response to pump faults, adds predictability and avoids unexpected shutdowns.
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.
Energy is the largest ongoing cost of mixer operation, so it is vital to carefully consider the energy-to-thrust ratio (sometimes called the “water-to-wire” ratio) for each and every mixer application.
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.
In the past year, the rate of acceleration in the cost of raw materials (including steel, iron ore, copper and aluminum) has reached unprecedented levels in the pump and rotating equipment industries.
An argument in favor of IEEE-841's provision for motor bearing protection.
In June, 2007, a reader asked Electrical Apparatus magazine, "How long should motor bearings last?" The answer will astound you:
"If (and it's a big if) ball bearings are kept clean and properly lubricated, their average or L-10 life should be 3 ½ centuries-3,180,000 hours."
The global economic downturn has resulted in an unprecedented attempt by world governments to help stimulate their individual economies, with the hope that these combined efforts will have a cumulative effect of breaking the downward spiral and lifting the global economy out of its crisis.
Latest Motors Articles
Electric motors have had a huge impact on the pump industry.
Improved motor starters help Fabri-Kal achieve its green vision.
Why integrating vibration monitors with process controls provides fast response to pump faults, adds predictability and avoids unexpected shutdowns.
The low voltage motors market is highly consolidated, with the top five participants accounting for more than 75 percent of the market revenues as of 2009. Low voltage alternating current (AC) motors dominate the industry, generating 92.1 percent of market revenues for 2009. That number is expected to increase to 95.9 percent by 2016, with a Combined Annual Growth Rate (CAGR) of 7.6 percent between 2006 and 2016. Low voltage direct current (DC) motors, on the other hand, are expected to have a negative 3.4 percent CAGR between those years.
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.
Last month we took a close look at the flow of voltage and current in purely resistive and inductive circuits. We showed how inductive reactance can inhibit the flow of primary current in a circuit and how this lagging effect determines the value of power factor (PF).
The global economic downturn has resulted in an unprecedented attempt by world governments to help stimulate their individual economies, with the hope that these combined efforts will have a cumulative effect of breaking the downward spiral and lifting the global economy out of its crisis.
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
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?
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.
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.
