CHAPTER 4 Motor Load factor Survey 4.1 Introduction Over sizing of equipment / induction motor can be measured in terms of load factor. Load factor is defined as the ratio between actual load to rated load. Load Factor of equipment / induction motor plays a major role on Energy Efficiency in Industry. It has been observed in many cases, the equipment is oversized from 50 to 100% of their actual requirement [4]. When the equipment put in operation the actual load factor may be 50 to 75%. A load factor study in industries was conducted to establish over sizing of Induction Motors / Equipment in Indian Industries. In south India, Textile Spinning Mills, Cement Industries and Engineering Industries are the major electrical energy consuming industries and energy cost plays a major role on profitability of these industries. An attempt was made to measure the load factor of induction motor during the detailed energy studies conducted in Textile Spinning, Cement and Engineering industries in Tamilnadu, Kerala, Karnataka and Andhra. The Indian Textile industry is one of the oldest in the country, more than 100 years old. The textile industry has undergone rapid changes over the years. There are more than 1200 number of operating units in the organized sector [2]. Out of the 1200 Textile Spinning mills in India nearly 900 spinning mills are located in South India. The textile spinning mills are the single largest industrial power consumer in Southern Regional Grid and having a power demand of 1250 MVA. The Typical cost of production and Profit Margin in Textile spinning mills in India is shown in the Table 4.1. Table 4.1 Cost of Production and Profit Margin in Textile Spinning Mills in India Sl.No Components of Cost Standard Spinning Mill in % Average Spinning Mill in % 1 Raw Material 55.0 57.0 2 Energy Cost 14.0 15.0 3 Salaries and Wages 9.0 7.5 4 Interest and depreciation 8.5 8.5 5 Others Costs 6.5 7.0 6 Stores 3.0 3.0 7 Profit Margin 4.0 2.0 Total 100 100 Source: South India Mills Association, Coimbatore (SIMA) 38
The Energy cost is the major manufacturing cost next to raw material cost in textile spinning mills. The scope for energy conservation estimated by Confederation of Indian industry in Indian textile sector is normally around 15% [16]. Hence energy conservation in a textile mill assumes significant importance. Cement Industry is one of the core industries, which plays a vital role in the growth of the nation. India ranks fifth among the cement producing countries in the world. There are 129 Large Cement plants in India. Out of the 129 large cement plants, 41 plants are located in Southern regional grid. Indian Cement Industry is the second largest consumer of energy in the country. Cement industries are one of the major energy intensive industries and having a demand of 576 MVA in Southern Regional Grid. The average energy cost accounts for nearly 40% of the total cost of manufacturing of Indian Cement Industry. On the basis of energy audit studies conducted by Confederation of Indian Industry, a saving potential of 10% exists in Indian Cement Industry [17]. Source: Indian Cement Manufacturers Association, New Delhi (www.cma.org) The third popular industry in South India is the Engineering Industries (Automobile and Automobile Spare parts manufacturing). Around 3000 Engineering Industries are in operation in Southern Regional Grid. Out of the 3000 Engineering industries in South India, nearly 1800 Units availing High Tension power supply from Southern Regional Grid. Tamilnadu Electricity Board, Chennai made Detailed Energy Audit mandatory for all HT Industrial Establishment. Industries having maximum demand more than 500KVA has to carryout detailed energy audit studies with the help of an approved energy auditor and submitted the energy audit report and implement the suggestion made for energy conservation. During the Detailed Energy Audit carried out by Energy Management Cell of Confederation of Indian Industry, Chennai and Thiagarajar College of Engineering, Madurai, an attempt was made to calculate the Load Factor of Induction Motors at site conditions. 4.2 Motor Load Factor Survey Motor Load factor plays a major role on Energy management in Industries. To estimate the motor load factor in various types of industries in South India, power measurement was carried out in induction motor as a part of work during the detailed energy studies in 14 Nos. of Spinning Mills, 39
9 Nos. of Dry Cement Industries, 9 Nos. of Engineering Industries and 4 Nos. of Weaving Mills. The power measurements are used to calculate the actual load factor of Induction motor at site conditions. The power measurements were done with the help of a Class 1 accuracy clamp-on power meter. The current rating of the CT used for the power measurement is 0-20 Ampere for 1.5 to 10HP motors, 0-200 Ampere for 12.5 HP to 100 HP motors and 0-1000 Ampere for 120 HP to 300 HP motors. The overall load factor Survey observations details are shown in the Table 4.2. Table 4.2. Overall Load Factor Survey Observations Detail 1 More than 100% 13 0.33 2 91 to 100% 14 0.35 3 81 to 90% 199 5.02 4 71 to 80% 505 12.73 5 61 to 70% 537 13.54 6 51 to 60% 798 20.12 7 41 to 50% 679 17.12 8 31 to 40% 432 10.89 9 21 to 30% 416 10.49 10 11 to 20% 320 8.07 11 0 to 10% 53 1.34 Total 3966 100.00 Table 4.3. Load factor details based on Motor Applications Sl.No Application Numbers Avg. Load Factor in % 1 Others 2457 51 2 Compressors 207 67 3 Elevators and Conveyor 457 35 4 Pumps 246 67 5 Fans and Blowers 599 57 Total 3966 40
Table 4.4. Load factor details in Engineering Industries 1 More than 100% 0 0.00 2 91 to 100% 1 0.23 3 81 to 90% 1 0.23 4 71 to 80% 63 14.35 5 61 to 70% 28 6.38 6 51 to 60% 84 19.13 7 41 to 50% 81 18.45 8 31 to 40% 75 17.08 9 21 to 30% 93 21.18 10 11 to 20% 5 1.14 11 0 to 10% 8 1.82 Total 439 100.00 Table 4.5. Load factor details in Textile Spinning Mills 1 More than 100% 11 0.79 2 91 to 100% 10 0.71 3 81 to 90% 182 13.00 4 71 to 80% 176 12.57 5 61 to 70% 224 16.00 6 51 to 60% 371 26.50 7 41 to 50% 233 16.64 8 31 to 40% 135 9.64 9 21 to 30% 54 3.86 10 11 to 20% 4 0.29 11 0 to 10% 0 0.00 Total 1400 100.00 41
Table 4.6. Load factor details in Cement Industries 1 More than 100% 2 0.11 2 91 to 100% 3 0.17 3 81 to 90% 9 0.52 4 71 to 80% 182 10.46 5 61 to 70% 214 12.30 6 51 to 60% 222 12.76 7 41 to 50% 273 15.69 8 31 to 40% 210 12.07 9 21 to 30% 269 15.46 10 11 to 20% 311 17.87 11 0 to 10% 45 2.59 Total 1740 100.00 Table 4.7. Load factor details in Textile Weaving Mills 1 More than 100% 0 0.00 2 91 to 100% 0 0.00 3 81 to 90% 7 1.81 4 71 to 80% 84 21.71 5 61 to 70% 71 18.35 6 51 to 60% 121 31.27 7 41 to 50% 92 23.77 8 31 to 40% 12 3.10 9 21 to 30% 0 0.00 10 11 to 20% 0 0.00 11 0 to 10% 0 0.00 Total 387 100.00 42
Table 4.8. Load factor details based on Motor Capacity Sl.No Capacity in KW No. of Motors Average Load Factor in % Variation in Load Factor 1 220 37 73 66 to 80 2 132 30 56 52 to 62 3 125 36 54 40 to 62 4 110 33 31 13 to 43 5 90 27 40 11 to 95 6 75 45 40 10 to 76 7 60 36 60 58 to 61 8 55 45 56 25 to 111 9 45 99 55 20 to 109 10 40 30 63 36 to 91 11 37 72 62 23 to 95 12 34 66 56 49 to 62 13 30 136 48 18 to 80 14 22 125 56 23 to 94 15 18.5 76 34 6 to 85 16 15 406 49 8 to 89 17 13 291 57 36 to 84 18 12.5 99 34 29 to 39 19 11 455 57 11 to 103 20 9.3 336 56 26 to 111 21 7.5 288 59 16 to 97 22 5.5 633 60 13 to 125 23 5 45 51 23 to 72 24 4.5 3 51 11 to 93 25 3.7 57 33 47 to 84 26 3.1 22 63 45 to 84 27 2.6 16 74 64 to 80 28 2.2 201 50 25 to 80 29 1.5 221 39 30 to 79 Total 3966 53 43
4.3 Observation made on the Load Factor Survey The load factor survey done in the 36 industries clearly indicates that the over sizing of induction motors / equipment are common. The average load factor in Industries located in South India is 53%, where as in European Union 57% [4]. Out of the 36 Industries 30 units has the maximum load factor of 80%. 94% of the motor populations are loaded less than 80% and 82% of the motor population loaded less than 70%. Out of the 3966 induction motors surveyed 309 are energy efficient motors.. The survey shows that most industries are still using the standard motor in their premises even though some of them have knowledge on energy efficient motor. This is due to several factors that delay the installation of the energy efficient motors. During the motor load factor survey, the numbers of motors controlled by advanced speed control drives are only 36. Pumps and Blowers are used in 845 Applications. Only in 12 Applications, Variable Speed drives are used to control the Pressure and Flow. Out of 845 Pump and Blower applications, 235 applications are constant Pressure and Flow applications. The Pressure and Flow variation application is 610 numbers. Out of the 610 Applications, 597 applications are controlled by conventional method of Pressure and Flow controls, such as Damper, Valve Throttling, and Recirculation. Majority of variable load Pump and Blower applications, the Pressure and flow is controlled from 30 to 70%. There is a large scope for conserving energy by installing variable speed drive to replace the conventional type of controls. The load factor survey conducted during year 2000 in the European Union countries France, Italy, United Kingdom, Germany and France clearly indicates the over sizing is common in industry. The surveys on the use of electric motors in the European countries highlighted that the average motors working far below the rated motor power. The average load factor among all surveyed sectors (food, paper, chemicals, ceramics, foundries and steel, tertiary sector) were estimated to range from 41% for small size motors (below4kw) to 51% for motors above 500KW. In food and tertiary sectors the average working load is even lower, with a minimum of 24% for smaller motors [4]. 44
The reasons why designers tend to oversize the motors are usually due to the aim of improving the reliability, to meet the starting torque requirements, ability to accommodate increasing power requirements, allowance for higher load fluctuations, operation under adverse conditions and inventory of spare motors [3]. The application wise break-up of Motor power utilization is shown in figure 4.1. Others 14% FHP Motor 4% Material Handling 8% Machine Tool 9% Fan 16% % Pump 31% Compresso r 18% Figure 4.1. Motor Power Utilization Application wise Break-up 4.4 Summary The over sizing of Induction Motors/ Equipment is common in Indian industry. 20% over sizing is observed in very few industries and 30% over sizing is observed in majority of Cement industries, Textile Spinning Mills and 40% and above over sizing is observed in many engineering industries. The variable frequency drives usage for efficient control is few in Indian industry. The use of energy efficient Induction motors are picking up in new industrial units installed after year 2000. The common reason for over sizing is to increase system reliability, to meet starting torque requirement and adhoc decision. Over Sizing of induction motor / equipment increase energy consumption and reduce the operating efficiency below the designed value. There is a need to develop techniques to conserve energy in Over Sized Induction motor / equipment. The Energy Management techniques developed based on 300 Case Studies carried out in 36 Industries in South India in over sized induction motor / equipment were discussed in chapter 5, 6 and 7. 45