ENERGY EFFICIENT MOTORS

ENERGY AUDIT AND DEMAND SIDE MANAGEMENTFINAL YEAR

DEPARTMENT OF EEE

PREPARED BY HARIKA.A

AITS-TPT

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UNIT-3

ENERGY EFFICIENT MOTORS

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CONTENTS INTRODUCTION

FACTORS AFFECTING EEM

EFFICIENCY & LOSS DISTRIBUTION

CONSTRUCTIONAL DETAILS

RMS HP LOADING

VOLTAGE VARIATION-UNBALANCE

VARIABLE DUTY CYCLE

MOTOR ENERGY AUDIT

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INTRODUCTION

Energy efficient motors (EEM) are the ones in which, design improvements are incorporated specifically to increase operating efficiency over standard motors.

Energy-efficient motors operate with efficiencies that are typically 4 to 6% higher than the standard motors.

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FACTORS AFFECTING EEMSTATOR AND ROTOR CU LOSSES

CORE LOSSES

FRICTION & WINDAGE LOSSES

STRAY LOAD LOSSES

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Power Loss Area Efficiency Improvement

1. Stator I2R

Use of more copper and larger conductorsincrease cross sectional area of statorwindings. This lowers resistance (R) of thewindings and reduces losses due to current

flow (I).

Rotor I2R

Use of larger rotor conductor bars increase size of cross section, lowering conductor resistance (R) and losses due to current flow (I).

Iron Use of thinner gauge, lower loss core steel reduces eddy current losses. Longer core adds more steel to the design, which reduces losses

due to lower operating flux densities.

Friction & Windage loss

Use of low fan design reduces losses due to air

movement.

Stray load losses Use of optimized design of slots numbers2/24/2015 6

Efficiency & loss distributionMotor performance

Power factor

Voltage variation

Motor load

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Constructional details

By increasing the amount of copper in the motor (≥60%)which reduces the resistance (Ohmic) loss in the winding &temperature rise. Performance improves because of increasedthermal mass.

Use of more & thinner laminations of high quality motorsteel reduces core losses in the stator and rotor.

Narrowing of air gap between stator and rotor increases theintensity of magnetic flux, thereby improving the motorability to deliver the same torque at reduced power.Increasing the length of stator and rotor increases the netflux linkages in the air gap to the same effect.

More complex rotor bar designs enable good starting torquewith efficient full speed operation.

Improved overall design reduces windage losses and strayload losses.

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RMS HP LOADING

This factor decides whether the motor will beapplicable for a particular cyclicing operation or not.

The RMS calculations take into account the fact thatheat build up within the motors is very much greaterat a 50% overload than it is under normal operatingconditions

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Calculation of RMS HP loading

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Contd..,

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Voltage variation & unbalance

Voltage unbalance is defined by the National Electrical Manufacturers Association (NEMA) as 100 times the absolute value of the maximum deviation of the line voltage from the average voltage on a three-phase system, divided by the average voltage.

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Contd..,

Voltage unbalance degrades the performance andshortens the life of motor.

Voltage unbalances at the motor stator terminals causesphase current unbalance far out of proportion thevoltage unbalance

Unbalanced currents lead to torque overheating, whichresults in a shorter winding insulation life

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Common causes for unbalance Faulty operation of power factor correction

equipment

Unbalanced or unstable utility supply

Unbalanced transformer bank supplying a three-phase load that is too large for the bank

Unidentified single-phase to ground faults

An open circuit on the distribution system primary

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Contd..,

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Motor Energy Audit Drive power is huge- think big,

Motors are part of a system –think systems,

Optimize the applications &process-deliverservice,

The further the downstream savings, the higher isthe upstream benefits-start downstream,

Pursue integration package of savingsopportunities rather than isolated measuresbecause many savings are inter –dependent –integrate measures

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Contd.., Collection of nameplate details of motor and load equipment Measurement of voltage, current, power, apparent power, power

factor, frequency and annual operating hours for major loads. Calculation of load factor for major loads. Checking for light loads on large motors Check if valves are always used for flow control in pumps, fans and

blowers. Check if flow from pumps, fans and blowers are changing

continuously. Check if the set discharge pressure is at the lowest permissible limit

of operation in the compressor. Check for proper maintenance of major equipment i.e. cleaning

measuring temperature, dust, vibration, noise, lubrication andcoupled condition.

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Power factor correction at motor end

Capacitors connected in parallel (shunted) with themotor are typically used to improve the power factor

The impacts of PF correction include reduced KVAdemand (and hence reduced utility demandcharges), reduced I2R losses in cables upstream ofthe capacitor (and hence reduced energy charges),reduced voltage drop in the cables

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Contd.., The size of capacitor required for a particular motor

depends upon the no-load reactive KVA (KVAr) drawnby the motor

Required capacitive kVAr increases with decrease inspeed of motor, as the magnetizing currentrequirement of a low speed motor is more compared tothe high speed motor for the same HP.

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Duty cycle It is a cycle that an entity remains in active state for a

total time period T is called duty cycle . For instanceconsider 1% of duty cycle i.e one cycle is in active stateout of 100 .therefore

Ton+ Toff = Duty cycle

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Need for using controls

Oversized motor

Varying Load

Adjustable speed capability can significantlyimprove productivity of many manufacturingprocesses by reducing scrap, enabling qualitymanufacturing during transition times and allowingmore control over start up and shut down.

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THANK YOU

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