1、NA-04-9-2a (RP-1104) Heat Loss from Electrical and Control Equipment in Industrial Plants: Part I-Methods and Scope Warren N. White, Ph.D. Anil Pahwa, Ph.D. ABSTRACT Accurate estimates of heat lost by power equipment facil- itate proper sizing of cooling and ventilation equipment required by buildin
2、gs and industrial plants. Information on heat loss is available in papers published in the 1970s und 1980s, but some of the information provided in these papers is dated and, in some cases, includes overly conservative assumptions. The main focus of this paper is to describe an effort to provide upd
3、ated informution on heat losses by various electric power devices. The information was gathered from equipment manufacturers and relevant standards associated with this equipment. Laboratory tests or mathematical simu- lations were done to determine heat loss for equipment with insuficient informati
4、on and to verib published data. A culo- rimeter was constructed for the testing of equipment. The construction and calibration of the calorimeter are described. Testprocedures used in acquiring loss data are described. For each equipment item in the scope of theproject, a description is provided as
5、to where und how the loss data were obtained. A summary of areas for future investigation is discussed. INTRODUCTION In order to size cooling and ventilating equipment, the HVAC design engineer must be able to estimate with certainty the amount of energy added from various heat sources and lost thro
6、ugh various heat sinks located in a room. Heat could be added from several sources such as the presence of many people in a classroom or office, solar radiation through windows, and room lighting. A sink could consist of outside doors and windows in winter or a basement floor or wall that remains at
7、 an essentially constant temperature throughout the year. By closely estimating the heat gain in a room or space, Chris Cruz the HVAC equipment will not be undersized with insufficient capacity or oversized with costly unutilized excess capability. Building and industrial plants make use of electric
8、al power for many uses such as lighting, driving motorized devices, HVAC, and energy distribution throughout the struc- ture. All of this electrical equipment contributes to the total heat load. Estimating the total amount of rejected heat is a necessary part of sizing the ventilating and cooling eq
9、uipment required for the building. The primary source of information available to the design engineer for estimating the electrical equipment rejected heat is the paper by Rubin (1979). In this often used document, the rejected heat values for transformers, power distribution equipment, motors, swit
10、chgear, and power cables, to name a few, were presented in tables for a range of equipment sizes common to indoor equipment. The data presented by Rubin were obtained from the paper presented by Hickok (1 978) and from other unspecified manufacturers. Hickok states that the data he presented were ob
11、tained exclusively from one manu- facturer. At no point in either Hickoks paper or in Rubins paper is there a discussion of measurement procedure or measurement uncertainty. Rubins motivation for publishing the data was to aid the HVAC design engineer. Hickoks moti- vation in his paper was to aid th
12、e factory engineer in identify- ing plant locations where efficiency could be improved. Hickoks motivation is easy to appreciate since the energy crisis provided by two oil embargoes made increasing efi- ciency of existing plants, buildings, and factories the first choice in reducing the costs of pr
13、oduction. McDonald and Hickok(1985) later issuedanupdate ofHickokspaper(1978) with much of the same data. Warren N. White is an associate professor and Chris Cruz is a graduate student in the Mechanical and Nuclear Engineering Department, and Anil Pahwa is a professor in the Electrical and Computer
14、Engineering Department, Kansas State University, Manhattan, Kans. 842 02004 ASHRAE. The information provided by these papers is dated. Since the oil embargoes of the 1970s, many electrical equipment manufacturers have increased the efficiency of their products. At the same time, advances in power el
15、ectronics and computer control have made much of the technology reflected in the 1970 equipment obsolete. Another change that has occurred since Rubin published his work is that the manufacturing stan- dards that apply to the various items of power equipment have been re-issued and updated several t
16、imes. These standards could provide details for measuring the power loss in the equipment where, perhaps, originally none existed. Also, the standards might specifi a maximum level of uncertainty for performing the measurements, and any data reported by a manufacturer claiming to follow the standard
17、 could be deemed reliable. Thus, there is a need to update the 20-year-old infor- mation originally presented by Rubin. A recent addition to the published information regarding motor heat gains is contained in Chapter 29 of the 2001 ASHRAE Handbook-Fundamen- tals that provides a table of “Heat Gains
18、 from Typical Electric Motors” for fractional horsepower AC motors up to 250 horse- power three phase motors. The purpose of this work is to provide a methodology for estimating the rejected heat of specific electrical equipment by means similar to Rubin and to account for updated data, current test
19、ing standards, level of use, and more than one power equipment manufacturer. This paper describes the work done in reaching the stated work purpose. The first part of this paper describes the methods of data collection and equipment testing together with areas for future work. The second part Equipm
20、ent Electric motors Medium-voltage switchgear (breakers, heaters, and auxiliary compartments) summarizes the data collection and test results and provides a comparison between the recently obtained information and that available from the cited earlier work. Size Range 10-4000 hp (reg. and high effic
21、iency) 5 kV, 7.2 kV, and 13.8 kV with 1200,2000, and 3000 amp breakers PROJECT SCOPE Transformers Reactors Panelboards The scope of the equipment investigated is listed in Table 1. Installed electrical equipment is normally not operated at 100% of full load on a continuous basis since no buffer woul
22、d exist to accommodate any unanticipated increase in power demand. As a result, it was necessary to be able to determine equipment heat loss at partial loads. In addition to heat loss at fractional loads, it was necessary to account for equipment diversity, i.e., the equipment being used only during
23、 a portion of the time. Early in the project, a distinction between types of heat transfer and operating conditions was drawn. The equipment rate of heat losses determined in this work represents constant values from steady operation. The device rejecting heat is assumed to have reached thermal equi
24、librium with the surroundings, and no thermal transient process is taking place. Thus, all heat loss occurring in a device is additional heat added to the surroundings. The manner in which the heat trans- fer takes place is not of concern. Heat convection to the surroundings and conduction to surrou
25、nding structures are not hard to appreciate as viable transfer mechanisms. Any thermal radiation is assumed to be absorbed by the surrounding struc- tures (perhaps after several absorptions and re-emissions), and 300-2500 kVA and 120/208/600 V units below 300 kVA Standard sizes Standard sizes for 12
26、0, 125, and 600 V Table 1. Equipment Investigated Battery chargers inverters 100 to 600 amp 20, 30,50,75, and 100 kVA-single phase 150 kVA-three phase 125 VDC for 100 to 1500 amp 1 DC switchgear Manual transfer switches Motor control centers (combination starters, breakers, auxiliary relay compartme
27、nts, bus losses, and space heaters) Unit substation components (including breakers, heaters, bus losses, and auxiliary compartments) 800, 1600,2000, 3200, and 4000 amp frame sizes 0.6 kV for 150,260,400,600,800, and 1000 amp Standard NEMA sizes Variable (adjustable) speed drives 1 Cable and cable tr
28、ays 10.6, 5, and i 5 kV of widths 12 in.-30 in. I 25 to 500 hp-three phase ASHRAE Transactions: Symposia 843 the eventual manifestation of the radiant energy is an increase in heat load. It should be pointed out that the radiant and convective split of heat loss is an important part of the cooling l
29、oad determination and should not be ignored. The data provided by this work are the total heat loss. How to split the loss will be a function of the device, enclosure, load, and appli- cation. METHODS OF DATA COLLECTION The initial stages of the project consisted of a literature review, review of ma
30、nufacturing standards for heat loss testing procedures, e-mailing requests for equipment loss data to the electrical equipment manufacturers, and examining manufac- turers Web sites and catalogs for heat loss information. The results of each of these inquiries are described in the following paragrap
31、hs. Based on the results of this initial survey, a test plan was developed. Surveys Outside of the works cited earlier by Hickock, Rubin, and McDonald, there are no other reported investigations involv- ing equipment heat loss. One notable and extremely usefiil reference uncovered during this search
32、 is the text by Anders (1997), which develops an extensive model of heat loss and temperature rise of cable bundles. The model presented by Anders is an extension of the original work of Neher and McGrath (1957). An updated cable model is presented by Harshe and Black (1994). In parallel to the effo
33、rt of reviewing literature, the manu- facturing standards for the equipment under study relevant to heat loss were identified. The identification process began by creating a list of manufacturing standards relevant to the type of equipment. This was first attempted by searching manufac- turers Web s
34、ites for the specific standards that were followed in the equipment production. An improved method of accu- mulating this information was through the Web sites of orga- nizations such as the National Electric Manufacturers Association (NEMA) and the Institute of Electrical and Elec- tronics Engineer
35、s (IEEE). In addition to the organizations just mentioned, standards from the American National Standards Institute (ANSI) and the Underwriters Laboratory (UL) were also reviewed. The list of relevant standards was refined by excluding those standards that did not address equipment heat loss or effi
36、ciency. Standards were found that covered heat loss measurement procedures for only the equipment categories of transformers, series reactors, battery chargers, and electric motors. Many of the standards reviewed were concerned with temperature rise since high temperatures promote insulation degrada
37、tion, yet only few treat heat loss or efficiency. The rele- vant transformer standards are IEEE Std. C57.12.90, IEEE C57.12.91, and NEMA TP 1 and NEMA TP 2. For electric motors, the essential standards are IEEE Std. 112, IEEE Std. 113,lEEEStd. 115,andNEMAMG 1. StandardIEEEC57.16 is the document deta
38、iling procedures for measuring series reactor heat loss, while NEMA PE 5 treats battery chargers. It was concluded that transformer and electric motor manufac- turers followed the standards cited from statements made on various manufacturers Web sites. However, no series reactor manufacturer was fou
39、nd to follow IEEE 07.16. The fact that standards covering heat loss measurements are followed by manufacturers is significant since published loss data are subject to the uncertainty levels specified by the standards; thus, the quality of the published information can be easily inferred. Heat loss i
40、nformation was found for battery chargers in the standard NEMA PE 5, covering utility type battery chargers; however, no manufacturer was found that claimed to follow this relevant standard that specifies how battery charger efficiency is to be determined. A side benefit of the standards search prov
41、ided informa- tion regarding the influence of ambient temperature on equip- ment heat losses. According to the cited standards, environmental temperature has only a small influence on transformer, motor, or series reactor heat losses. In this work, one very important source of information is equipme
42、nt manufacturers. Manufacturers of a particular equipment item were located through a search of the NEMA Web site. This search provided the starting point for any contact with equipment manufacturers since postal and e-mail addresses were available. Contact through e-mail was made to the companies i
43、ncluded on the manufacturer lists to inquire about dissipated heat from their products. Since a contact was being made with equipment manufacturers, information not only relevant to the classification was sought but also information useful to other parts of the study. For each type of power equipmen
44、t involved in the survey, a contact letter was written that explained the nature of the project and requested information relevant to this study. The requested information consists of the name and number of the standards followed in determining the loss numbers or the procedures used to determine th
45、e losses in the case where no loss determination procedures are specified in the standards. Also, the manufacturer was requested to supply loss numbers for its products or to specify the Web pages and or public company documents where loss figures are presented. This step was not done for every piec
46、e of equipment under study, e.g., cables, since it was not expected that power losses would vary from manufacturer to manufacturer and excellent mathematical cable loss models are available. Each of the equipment types was documented regarding applicable standards, loss measurement methods, availabi
47、lity of loss data, and results of the manufacturer survey. From the accumulated data, the equipment was classified into one of three categories. The first category consisted of those products for which the standards require specific, well-defined tests for loss determination and reporting in additio
48、n to the availability of published loss information. The third category includes equipment for which there was no standard either requiring or describing any heat loss tests and for which no heat loss data could be found. The second category included ail equipment satisfying neither of the first nor
49、 third category descriptions. a44 ASHRAE Transactions: Symposia Items in the second category represent a wide range of differ- ent situations or conditions. The best description for this cate- gory is that information was available on equipment heat losses, but the measurement quality was unknown. The first category included transformers and motors. The devices in the second category were reactors, medium-voltage switchgear, circuit breakers, motor control centers, inverters, battery chargers, adjustable-speed drives, plus cables and cable trays. The remainder of the power equipment
