Electrical Engiineer, Thesis of Energy Efficiency

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ENERGY MANAGEMENT

SYSTEMS

Southern School of Engineering and

Technology

DEPARTMENT OF ELECTRICAL ENGINEERING

Dr. Muhammad Abrar

ELECTRIC ENERGY MANAGEMENT

Use of Electrical Energy  Used to run electric motor driven systems.  The cost effective way is to check each component of the system for an opportunity to reduce electrical losses.  A qualified individual should oversee the electrical system since poor power distribution within a facility is a common cause of energy losses.

Opportunities to improve drive system efficiency.  (^) 1. Maintain Voltage Levels.  (^) 2. Minimize Phase Imbalance.  (^) 3. Maintain Power Factor.  (^) 4. Maintain Good Power Quality.  (^) 5. Select Efficient Transformers.  (^) 6. Identify and Fix Distribution System Losses.  (^) 7. Minimize Distribution System Resistance.  (^) 8. Use Adjustable Speed Drives (ASDs) Motors Where Appropriate.  (^) 9. Consider Load Shedding.  (^) 10. Choose Replacement Before a Motor Fails. Items to help facility management staff identify opportunities to improve drive system efficiency.

POWER SUPPLY The power supply is one of the major factors affecting selection, installation, operation, and maintenance of an electrical motor driven system. Motors designed for rated voltage, frequency, and number of phases. The supply voltage must be known to select the proper motor. Motor nameplate voltage will normally be less then nominal power system voltage. Operation within tolerance of 10 percent of the rated voltage. Operation from a sine wave of voltage source (not to exceed 10 percent deviation factor. Operation within a tolerance of 5 percent of rated frequency. Operation within a voltage unbalance of 1 percent or less. Operation at other than usual service conditions may result in the consumption of additional energy.

EFFECTS OF UNBALANCED VOLTAGES 

Unbalanced Defined:

Example—With voltages of 220, 215 and 210, the average is 215, the maximum deviation from the average is 5 PERCENT VOLTAGE UNBALANCE = 100 * 5/215 = 2.3 PERCENT

MOTOR

The purpose of an

electric motor is to

convert electrical energy

into mechanical energy.

GLOSSARY OF FREQUENTLY

OCCURRING MOTOR TERMS

 Efficiency Efficiency= EFF = 746 × HP Output/Watts Input  Frequency This is the frequency for which the motor is designed.  Full Load Speed An indication of the approximate speed that the motor will run when it is putting out full rated output torque or horsepower is called full load speed.

Load Types  Constant Horsepower The term constant horsepower is used in certain types of loads where the torque requirement is reduced as the speed is increased and vice-versa. The constant horsepower load is usually associated with metal removal applications such as drill presses, lathes, milling machines, and similar types of applications

 Constant Torque Constant torque is a term used to define a load characteristic where the amount of torque required to drive the machine is constant regardless of the speed at which it is driven. For example, the torque requirement of most conveyors is constant. Load Types

 Phase Phase is the indication of the type of power supply for which the motor is designed.  Poles This is the number of magnetic poles within the motor when power is applied. Poles are always an even number such as 2, 4, 6. In an AC motor, the number of poles work in conjunction with the frequency to determine the synchronous speed of the motor

GLOSSARY

 Power Factor

Percent power factor is a measure of a particular

motor’s requirements for magnetizing amperage.

Power Factor = pf = Watts Input/ Volts × Amps × 1.

 Service Factor

The service factor is a multiplier that indicates the

amount of overload a motor can be expected to handle.

For example, a motor with a 1.0 service factor cannot

be expected to handle more than its nameplate

horsepower on a continuous basis. Similarly, a motor

with a 1.15 service factor can be expected to safely

handle intermittent loads amounting to 15% beyond its

nameplate horsepower.

GLOSSARY

 Synchronous Speed This is the speed at which the magnetic field within the motor is rotating. It is also approximately the speed that the motor will run under no load condition. For example, a 4 pole motor running in 60 cycles would have a magnetic field speed of 1800 RPM. The no load speed of that motor shaft would be very close to 1800, probably 1798 or 1799 RPM. The full load speed of the same motor might be 1745 RPM. The difference between the synchronous speed of the full load speed is called the slip RPM of the motor. GLOSSARY

 Temperature  Ambient Temperature. Ambient temperature is the maximum safe room temperature surrounding the motor if it is going to be operated continuously at full load. In most cases, the standardized ambient temperature rating is 40°C (104°F). This is a very warm room. Certain types of applications such as on board ships and in boiler rooms, may require motors with a higher ambient temperature capability such as 50°C or 60°C.  Temperature Rise. Temperature rise is the amount of temperature change that can be expected within the winding of the motor from non- operating (cool condition) to its temperature at full load continuous operating condition. Temperature rise is normally expressed in degrees centigrade. GLOSSARY