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Selecting Efficiency and Estimating Savings

High efficiency motors can help minimize your motor operating costs. Because many motors operate 40-80 hours per week or more, even small increases in efficiency can yield substantial energy and money savings. Efficiency: the ratio (in percent) of mechanical power output to the electrical power input.

Fig1 : Lifetime Motor CostsEquation 1.Motor Efficiency Energy Cost Savings Equation

Example Annual Energy Cost Savings Calculation with Upgrade to NEMA PremiumEstimated annual dollar savings associated with replacement of a totally enclosed fan cooled (TEFC) 150hp,1800 rpm motor below EPAct efficiency standards with a NEMA Premium motor of the same size and type.This calculation assumes both motors have the same load factor, 75% Motor dataMotor Power (hp) 100 hpLoad Factor (LF)% 75%Annual Operation hours 5,200 hoursMotor 1 efficiency 93.0%Motor 2 Efficiency 95.8% premiumElectricity cost (Rm/ Kwh) 0.07/kwhNational Electrical Manufacturers Association (NEMA)

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Equation 2.Motor Energy Demand Savings Equation

Example Energy Demand Savings Calculation with NEMA Premium Motor

The most common type of general-purpose motors found in industrial motor systems are squirrel cage induction motors.These motors are generally referred to as“general-purpose motors.” Motor SpeedEquation Synchronous Speed Calculations power consumption is related to speed,the higher speed can lead the motor to draw more power.

Estimating Energy and Cost Savings with ASDs

Matching motor speed to application requirements through the use of ASDs,

also referred to as VFDs or inverters, can achieve significant electricity savings when

connected to motors in appropriate applications such as centrifugal pumps and fans

ASDs can provide additional benefits related to energy efficiency

Improved process control, such as speeding up or slowing down a machine or process:

Inherent power factor correction

Bypass capability in the event of an emergency

Protection from overload currents

.EquationAnnual Energy Cost Equation for Motor-Driven System with ASD

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Potential Savings with ASD on Centrifugal Loads

Below,a 50hp centrifugal pump operating 4,067hours annually,with a 75% load factor, a

throttling valve to regulate flow to 70% on average, and primarily frictional losses and

negligible static head.

Pump System dataMotor Power (hp) 50 hpMotor Efficiency (Emotor) 0.93 (1800 rpm)Load Factor (LF)% 75%Percent full rated speed 100%Annual operating hours 4,067 hoursElectricity cost 0.07/kwhASD Efficiency (EASD) 97%

Fig :Pump System Diagram with Throttling Valve

Annual Energy Cost Calculation with Throttling Valve in Pump System

The same system appears below, except an ASD replaces the throttling valve to achieve the same flow regulation by varying the motor’s rotational speed

Fig :Pump System Diagram with ASD

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Annual Energy Cost Calculation with ASD in Pump System

Annual Energy Cost Savings Calculation Associated with ASD in Pump System

Electric Demand Savings Equation with ASD in Pump System

Electric Demand Savings Calculation with ASD in Pump System

Using the information from each scenario, potential savings are calculated: replacing the

throttling valve with the ASD can achieve approximately $4,238 in annual energy cost

savings and saves approximately 15kW of electric demand

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Report on

Study on International Efficiency (IE) Efficiency Classes for AC Motors

Purpose To promote higher energy efficiency to reduce the energy consumption and the

energy cost of high voltage AC motors.

To facilitate the procurement of new motors with higher energy efficiency, a study

on the IE and its application was conducted.

A case study on calculating the energy saving of replacement of energy efficient motor

is covered

a survey on the motor and its price of different classes from major suppliers in Malaysia

EFF Classification

The EFF has 3 classes, i.e. EFF1, EFF2 and EFF3 respectively. EFF1 is the most energy

efficient, while EFF3 is the least energy efficient.

Alignment of the energy efficiency standard of CEMEP and IECEfficiency Class IEC CEMEPSuper Premium Efficiency IE4

Motor Energy Saving Calculation FormEmployee Name: Location:Company: Process:Date:Motor Nameplate&Operating InformationManufacture: Full Load speed:Motor ID NO: Full load amperage:Size(hp): Full-Load Power Factor (%)Enclosure Type: Full-Load Efficiency (%)Synchronous speed: Annual Operating Time ______ hours/yearUtility RatesEnergy Rate ($/kwh):………………………….Monthly Demand Charge ($/kW/mo.)Annual Operating Hours (hrs/yr.)Annual Energy Use and CostInput Power (kW)Annual Energy Use < Input Power x Annual Operating Hours >

Annual Energy Cost: < Annual Energy Use x Energy Rate >

Total Annual Cost: < Annual Energy Cost + Annual Demand Cost >

Motor Load and Efficiency Determination

Load : < Input Power(kW) / [ Motor Size(hp) x 0.746 / Efficiency at Full Load ] >

Motor Efficiency at Operating Load:

Energy Savings and Value

kW saved=< Input Power - [ Load x hp x 0.746 / Efficiency of Replacement Motor at Load Point ]>

kWh saved < kW saved x Annual Operating Hours>

Total Annual Savings

Total Annual Savings < (kW saved x 12 x Monthly Demand Charge) + (kWh saved x Energy

Rate)>

Economic Justification

Payback (years)

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Premium Efficiency IE3High Efficiency IE2 EFF1Standard Efficiency IE1 EFF2Below Standard Efficiency EFF3

The scope of classification is defined for single speed, single and three phase, and

continuous duty electric motor with 2, 4, 6 or 8 poles. The rated output ranges from

0.75kW to 375 kW; and the frequency is between 50Hz and 60Hz. The scope also

includes ambient temperature within the range of -20o C to +60o C and an altitude of up

to 4,000m above sea level.

In accordance with the Malaysia electricity supply context, 50Hz motor is the focus. It is

observed that the motors commonly used in Malaysia are 4-poles. A graphical

presentation of this type of motor is shown in Figure 1 while the minimum energy

efficiency requirement of IE Efficiency Class of IE1 to IE4 of different poles is shown

in Table . .

Motors market and priceIn Table . The motors are divided into 2 groups in accordance with their rated power of

37kW due to the significant difference of their shaft bearing design.

The listed prices are obtained from various manufacturers available in market The listed

price of IE2 4-poles 7.5 kW motor is around $6,000 market

The listed price of IE2 4-poles 45kW motor is around $28,000 in market.

Rated Power kw IE2 IE3 IE4

≤37 1.00 1.17 ratio 1.32 ratio>37 1.00 1.13 1.21

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Energy Saving by Energy Efficient MotorThe annual energy saving by upgrading to more efficient motor is calculated as the formula below:

The percentage of energy saving can be calculated with the following formula:

If the annual energy consumption of motor is not available, it can be estimated with the following formula:

Case StudyTo demonstrate the calculation of energy cost saving and payback period, a case study is provided below. For Company A, the information regarding the old motor and the operation pattern is shown in Table

Table Specification of old motor and operation pattern .Rated Power 37 kWNo. of Poles 4 Efficiency 91.2 (IE1) Operating Hours per Day 10Operating Days per Year 360

The Annual Energy Consumption is calculated below:

Therefore, the annual energy consumption of old motor is 146,052kWh. 10 of 13 Company A is going to upgrade the motor to an IE3 motor as per the specification shown in TableTable Specification of new motorRated Power 37 kWNo. of Poles 4Efficiency 93.9 (IE3)Cost of Motor (including installation) 40,000 $Designed lifespan 400,000 hours

The percentage of energy saving and the anticipated annual energy saving is calculated below:

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Therefore, the percentage of energy saving and annual energy saving is 2.88% and 4,206kWh per year, respectively.

To evaluate the cost effectiveness, the payback period is calculated as follows:

Therefore, the payback period is 9.5 years, which equals to 34,675 operating hours. In comparison with the designed lifespan of the motor (i.e. 400,000 hours), upgrading the motor from IE1 to IE3 is considered to be cost effective.

Table Minimum Energy Efficiency Requirement of IE Efficiency Class IE1 to IE4 for 50 Hz motors

‘How much electrical power may realistically be saved by using high or premium efficiency motors’?

Let us compare energy and capital costs on two motor sizes and efficiencies. We will consider 7.5kW IE1, IE2 and IE3 motors as well as a 75kW IE1, IE2 and IE3 motors.

Referncehttp://www.beeo.emsd.gov.hk/en/pee/BEC_2015.pdf(code of practice for Energy Efficiency of Building Services Installation)

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file:///C:/Users/user/Downloads/4E_Roadmap_for_Motors_and_VFD_231115_v3.pdfhttp://www.zvei.org/Publikationen/ZVEI%20Electric%20Motors%20and%20Variable%20Speed%20Drives%202nd%20Edition.pdf