Energy Efficient Motors

Upgrading even one, 0.75 kW motor to a Premium Efficient motor gives double

benefit of Energy Savings and Carbon credits....

Every year will eliminate:

1 Drum of Oil from being burned

250 Kg of coal from being burned

Up to 650 gms. of carbon emissions from being released into the atmosphere

and....

or....

LOSSES1 . Core loss represents energy required to magnetizethe core material (hysteresis) and includes lossesdue to creation of eddy currents that flow in thecore. Core losses are decreased through the use ofimproved permeability electromagnetic (silicon)steel and by lengthening the core to reduce magneticflux densities. Eddy current losses are decreasedby using thinner steel laminations.

2. Windage and friction losses occur due to bearing friction and air resistance. Improved bearing selection , air-flow, and fan design are employed to reduce these losses. In an energy-efficient motor , loss minimization results in reduced cooling requirementsso a smaller fan can be used. Both corelosses and windage and friction losses are independent of motor load.

3. Stator losses appear as heating due to current flow

(I) through the resistance (R) of the stator winding.

This is commonly referred to as an I2R loss. I2R

losses can be decreased by modifying the stator

slot design or by decreasing insulation thickness to

increase the volume of wire in the stator.

4. Rotor losses appear as I2R heating in the rotor Rotor losses can be reduced by increasing the size of the conductive bars and end rings to produce a lower resistance, or by reducing the electricalcurrent.

5. Stray load losses: are the result of leakage fluxes induced by load currents. Both stray load losses and stator and rotor I2R losses increase with motor load.

Motor Loss Categories Typical Factors AffectingNo Load Losses Losses (%) these Losses

1.Core Losses 15 -25 Type and quantity of magnetic material2.Friction and Windage Losses 5 – 15 Selection and design of fans and bearingsMotor Operating Under Load3.Stator I2R Losses 25 – 40 Stator conductor size

4.Rotor I2R Losses 15 – 25 Rotor conductor size

5.Stray Load Losses 10 – 20 Manufacturing and design methods

Description of Motor component’s Losses:

Copper Loss: Depends on the effective resistance of motor winding: Caused by the current flowing through it.

Is equal to I²R

Proportional to Load. Is equal to Stator I²R + Rotor I²R Loss.

Iron Loss:

Depending on the magnetic structure of the core and results from a combination of hysteresis and eddy current effect due to changing magnetic fields in the motor’s core Voltage Related

Constant for any particular motor irrespective of load.

Friction and Windage loss:

Occurs due to the friction in the bearing of the motor.

The windage loss of the ventilation fan, other rotating element of the motor.

Depend on the bearing size, speed type of bearing, lubrication used and fan blade profile.

Constant for given speed irrespective of load.

Stray Loss:It is very complex and Load related.

Arises from harmonics and circulating current.

Manufacturing process variations can also add to stray losses.

What is an energy efficient motor?   An “Energy efficient” motor produces the same shaft output power (kW), but draws less input power (kW) than a standard (lower efficiency) motor.

Hence EEM consumes less electricity than comparable standard motor for any given load.

    EEM are manufactured with higher quality materials and techniques; they usually have higher service factors and bearing lives, less waste heat output and less vibration.

Features of EEM: Highest efficiency.

Lower operating cost.

Has high overloading cost.

Suitable for operations at higher ambient temperature.

  Fewer power factor correction

Saving increases with time.

Confirmation with NEMA standards of protection and control.

Cooler and Quieter operation.

Longer insulation life : EEM’s winding run about 20˚C cooler which increases insulation life by 4 times.

Improved bearing life: EEM bearing run about 10˚C cooler than standard motor bearing, which doubles the life. Less Starting thermal stress.

Higher service factor.

Better suited for energy management systems.

EEM perform better under adverse conditions of abnormal voltage conditions like unbalanced voltages. Efficiency of EEM remains almost constant from 50% to 100% of load.

Minimising losses in a motor

1. Iron Losses•Improved steel properties :Standard motors use low carbon laminated silicon steel for the rotor and stator. Such steel typically has electrical losses at 606 watts/kg. High efficiency motors are build with high grade silicon steel which typically reduces hysteresis and eddy current losses by half to only about 3.3 watts/kg.

Thinner Laminations:•Reducing lamination thickness in rotor and stator steel also lowers eddy current losses•Improved insulation between laminations, when applied with enhanced quality control further reduces these losses. •The use of thinner lamination result into decrease in core loss from 10% to 25% depending on method of processing the lamination steel and the method of assembling the magnetic core. •Longer core adds more steel to the design, which reduces the losses due to lower operating flux densities.

2.Stator and

Rotor I²R Losses

1.Increase conductor volume:•Older standard motors employ aluminium or copper conductors of size no larger than that needed to deliver the required horsepower •High efficiency motors utilize bigger copper conductor to lower the winding resistance with the conductor sized 35% to 45% larger than needed to simply satisfy the motor output horsepower requirement.

Modified slot design :

•To accommodate the larger volume of copper in the windings & required additional slot insulation, the slot cross section area is increased.

Friction and Windage Losses

• More Efficient fan design:a. Use of low loss fan design reduces air

movement.b. Use of better quality bearing and

lubricating material reduces friction losses.

c. In EEM the heat producing losses are low hence it is possible to reduce ventilating requirements which in turn will reduce

windage losses resulting into further improvement of the efficiency.

d. EEM design incorporates a small cooling fan resulting into quieter operation

Stray Losses

a. Use of optimized design and strict quality control procedures minimizes the stray losses.

b. Proper proportioning of rotor and stator slots.

c. Having Small slot opening.d. Using optimum air gap.

Air Gap

Narrowing air gap:• Air gap are optimized to reduce magnetizing

current and associated losses resulting into improvement of power factor.

http://www.energysmartmotors.org/images/different_motor.gif

Application:

Energy efficient motors are specially suited for industries which are power intensive and equipments which run on constant load for long duration.

Examples :

Fans, Blowers, Mixers, Pumps, Compressors etc. are some of the driven

equipment's and industries such as textile, paper, rubber,

petrochemicals, cement, power generation etc are those that are suited for such motors

What Design Characteristics are Important?

1 Motor Size Motors should be sized to operate with a load

factor between 65% and 100%. The common practice of oversizing results in less efficient motor operation. For rare peak loads, use a pony motor.

2 Operating Speed While the average speed of energy-efficient

motors is slightly higher than the average speed of standard-efficiency motors for any given size, models of each type are available with a wide range of speeds.

Installing a new motor with a higher speed can result in diminished energy savings. It is particularly important in centrifugal pump or fan applications to select replacement motors with a comparable full-load speed.

3 Inrush Current Avoid overloading circuits. Energy-efficient

motors feature low electrical resistance and thus exhibit higher inrush currents than standard models. The inrush current duration is too short to trip thermal protection devices, but energy-efficient motors equipped with magnetic circuit protectors can sometimes experience nuisance trips during start-up.

Opportunities for choosing energy efficient motors:

(1) When purchasing a new motor

(2) In place of rewinding failed motors,

(3) To retrofit an operable but inefficient motor

INCENTIVES

Please Remember

• Energy costs every hour but motor costs only once and paysback to the owner for the rest of its life 0f 25-30 years.

• Saved Energy can be sold to earn profits.

Thank You