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Pumps & Systems, October 2008

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.

Pumps & Systems, June 2008

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.

Pumps & Systems, June 2008

An argument in favor of IEEE-841's provision for motor bearing protection.

Pumps & Systems, June 2008

Due to the expense and labor required, most facilities need to maximize the life of their motors. Electrical, insulation resistance and thermal measurement are three tests that can troubleshoot motors, drives and associ­ated electrical panels and prolong their operational lifetime. Ther­mal imagers can detect potential problems and insulation resistance and electrical tests can deter­mine the cause.

Pumps & Systems, June 2008

A common mistake when troubleshooting a motor failure is to focus attention only on the motor. The perception is if the motor is failing, the problem must be the motor, but this is the wrong approach.

Pumps & Systems, June 2008

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.

Pumps & Systems, June 2008

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.

Pumps & Systems, June 2007

Why integrating vibration monitors with process controls provides fast response to pump faults, adds predictability and avoids unexpected shutdowns.

Pumps & Systems, June 2007

In many pump installations, problems such as jams and suction loss can lead to serious damage to the motor or pump long before the thermal overloads trip. These problems can be quickly detected by monitoring drive motor current.

Pumps & Systems, June 2007

When a motor fails, users can (1) rewind, possibly for high efficiency; (2) replace the failed motor with a new motor; or (3) invest in a premium efficiency product. Here are the advantages and disadvantages of each approach and the precautions that must be taken to assure the best investment.