Distribution Equipment & Motors

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Poor power distribution within a facility is a common cause of energy losses. Properly designed, installed and maintained electrical systems will meet safety codes, minimize downtime and reduce electrical losses.

• Avoid poor voltage problems
• Avoid low power factor
• Select efficient transformers
• Identify and eliminate distribution system losses through maintenance
• Improve efficiency of motors
• Check motors regularly
• Improve electric motors for efficiency

Avoid poor voltage problems

Good voltage at the utilization point is essential for proper performance and the efficient use of energy. Avoid poor voltage problems by:

• Matching the equipment voltage rating with the service voltage
• Sizing wiring for voltage drop limits by
• Selecting the highest practical voltage available
• Selecting proper conductor sizing

To maintain voltage levels:

• Motor voltages should be kept as close to the nameplate value as possible, with a maximum deviation of 5%. Although designed to operate within 10% of nameplate voltage, large variations significantly reduce efficiency, power factor and service life.
• When operating at less than 95% of their designed voltage, motors typically lose 2 to 4 points of efficiency and service temperatures increase up to 20º F-greatly reducing insulation life.

Avoid low power factor

Low power factor results when induction motors are operated at less than full load and it reduces the efficiency of the electrical distribution system both within and outside of your facility.

Install capacitors either at the motor or motor control centers to address low power factor problems.

Select efficient transformers

Install efficient and properly sized step-down transformers. Older, underloaded or overloaded transformers are often inefficient.

Identify and eliminate distribution system losses through maintenance

• Regularly check for bad connections, poor grounding and shorts to ground. Such problems are common sources of energy losses, hazards and reduced system reliability.
• During the annual maintenance cycle for your power distribution equipment, perform an infrared scan for "hot spots" (signs of electricity losses) and then ensure that all loose connections are tightened.

Improve efficiency of motors

• Use adjustable speed drives (ASDs) or two-speed motors where appropriate. These can reduce electrical energy consumption in centrifugal pumping and fan applications - often by 50% or more.
• Use controls to turn off idling motors. The maximum number of on/off cycles per hour and the maximum amount of time off between cycles are affected by: motor size; motor speed; and the type of load (variable or fixed).
• Optimize motor efficiency by making certain the motor is properly sized. Oversizing and underloading can lead to low power factor and increased losses.
• Keep motors cool because high temperatures reduce insulation life and motor reliability.

Check motors regularly

• Check motors often to identify potential problems. Inspections should include daily or weekly noise, vibration and temperature checks.
• Twice yearly, test winding and winding-to-ground resistance to identify insulation problems.
• Periodically check bearing lubrication, shaft alignment and belts.
• Ensure certain motors are shaded from the sun, are located in well-ventilated areas and are kept clean (dirt acts as an insulator).
• Lubricate motors according to manufacturer specifications. Apply high-quality greases or oils carefully to prevent contamination by dirt or water.

Improve electric motors for efficiency

In general, electric motors account for 60% of electric use in commercial and industrial facilities. Here are some tips for saving energy with motors:

• Replace motors with correctly sized new motors. Existing motors are often oversized or undersized, resulting in operation at less than optimal efficiencies.
• Remember to use soft start motor controllers for reducing inrush current. This will help prolong the life of your motor.
• Keep your motors as cool as possible by avoiding locations in direct sunlight and high heat areas. If this is not possible add cooling fans.
• If you have a power quality meter add a thermister temperature probe to each motor. You can then monitor the temperature of each motor in real time. Many meters sound an alarm if any motor exceeds temperature thresholds. Doing this could add several years to your motor life and pay for the cost of the metering.