ASHRAE AB-10-025-2010 Heat Gain from Electrical and Control Equipment in Industrial Plants-Part 2.pdf

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1、618 ASHRAE TransactionsThis paper is based on findings resulting from ASHRAE Research Project RP-1395.ABSTRACTRP-1395 is a continuation of an earlier project where the heat dissipated by indoor power distribution equipment is esti-mated. In RP-1104 certain equipment were examined while others were n

2、ot. The goals of RP-1395 was to provide verifi-cation of some of the information presented in RP-1104 and to investigate other types of equipment not previously covered. The scope of RP-1395 is presented and the project results are summarized. Certain RP-1395 equipment items are not presented here b

3、ecause these devices have been adequately treated in recent publications. The equipment items not covered in this paper are medium and low-voltage switchgear and adjustable speed drives.INTRODUCTIONIn order to size the cooling equipment, the HVAC design engineer must be able to estimate with certain

4、ty the amount of energy added to the environment from various heat sources and lost through various heat sinks located in a room. Heat could be added from several sources such as the presence of people in a classroom or office, solar radiation through windows, and incandescent room lighting. A heat

5、sink could consist of outside doors and windows in winter. By closely estimating the environmental heat gain, the HVAC equipment will not be incorrectly sized with insufficient capacity or costly unutilized excess capability.Building and industrial plants utilize electrical power for many uses such

6、as lighting, driving motorized devices, HVAC, and energy transmission and 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 heating and refrigeration equip-ment r

7、equired for the building.Until recently, the primary source of information avail-able to the design engineer for estimating the environmental heat gain caused by electrical equipment is the paper by Rubin (1979). In this well used document, the rejected power values corresponding to full load operat

8、ion for transformers, power distribution equipment, motors, switchgear, and power cables, to name a few, were presented in tables for a range of equip-ment sizes common to indoor equipment. The data presented by Rubin was obtained from the paper presented by Hickok (1978) and from other, unspecified

9、 manufacturers. Hickok, who worked for GE at the time of publication of his paper, states, “The data are on General Electric products ” At no point in either Hickoks paper or in Rubins paper is there a discussion of measurement procedure or measurement uncer-tainty nor is there any information on th

10、e rate of heat dissipa-tion caused by part loads. Rubins motivation for publishing the data was to aid the HVAC design engineer. Hickoks moti-vation in his paper was to aid the factory engineer in identify-ing plant locations where efficiency could be improved. Hickoks motivation is easy to apprecia

11、te because the energy price shocks provided by two oil embargoes made increasing the efficiency of existing plants, buildings, and factories the first choice in reducing the costs of production. McDonald and Hickok (1985) later co-authored an update of Hickoks 1978 paper with much of the same data.T

12、he information provided by these papers is dated. Since the oil embargoes of the 1970s, many electrical equipment manufacturers have taken pains to increase the efficiency of Heat Gain from Electrical and Control Equipment in Industrial PlantsPart 2Warren N. White, PhD Emilio C. PiesciorovskyWarren

13、N. White is an associate professor in the Department of Mechanical and Nuclear Engineering, and Emilio C. Piesciorovsky is a grad-uate student in the Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS. AB-10-025 (RP-1395)2010, American Society of Heating, Refri

14、gerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions (2010, Vol. 116, Part 2). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission.2010 ASHR

15、AE 619their products. At the same time, advances in power electron-ics 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 manu-facturing standards that apply to the various items

16、of power equipment have been re-issued and updated several times. These standards could provide details for measuring the power loss in the equipment where, perhaps, originally none existed. Also, the standards might specify a maximum level of uncer-tainty for performing the measurements and any dat

17、a reported by a manufacturer claiming to follow the standard could be deemed reliable. Thus, there is a need to update the 30 years old information presented by Rubin.White and Pahwa (2003a) report on work undertaken to provide new, up-to-date equipment power loss data as well as information on loss

18、es corresponding to part load operation. A result of RP - 1104 was the issuance of a proposed design guide for estimating the environmental heat gain. The scope of the work was reported in White, Pahwa, and Cruz (2004a) while a synopsis of the design guide was reported in White, Pahwa, and Cruz (200

19、4b). While good strides were completed in the work of White et al., RP-1104 was just a beginning in the development of accurate ways of estimating the rejected heat of indoor electrical distribution equipment.The purpose of this work is to continue and advance the effort initiated in RP-1104. The sc

20、ope of the work is outlined in the following section.Scope of WorkTable 1 lists the types of indoor electrical equipment that were investigated. In each row, the capability of estimating the equipment heat loss at the initiation of the project is stated. Also, the information needed in each equipmen

21、t category is stated. The scope of the work to be performed in each equip-ment instance is stated and, finally, the work performed is listed. The differences between the proposed and actual work scope will be explained on a case by case basis.In the sections to come, each of the equipment categories

22、 will be covered and the results will be summarized.PROJECT RESULTSDC or Telecom SwitchgearDC or telecom switchgear has the technical name of switch mode rectifiers and consists of 12/24/48 volt rectifiers for battery charging and powering DC loads. The rectifiers are driven by the AC power supply.O

23、riginally, the plan was to measure the power loss of such devices and compare the results to published manufacturer data in order to assess the quality of the numbers provided by manufacturers. Because switch mode rectifier test results were found in the technical literature, these published results

24、 were used in lieu of tests.The switch mode rectifier (SMR) unit is a solid state elec-trical device that transforms the AC input voltage from the util-ity power supply, namely 120/208 VAC for the USA and 220/380 VAC for the EU, into a DC output voltage consisting of either 12, 24, or 48 VDC. This D

25、C voltage output is usually used to feed telecommunication applications. Some SMR units can be packaged with a battery option which provides the backup power during the AC outages.The percent of rated load, P, is defined as(1)where Pris the SMR rated power in watts (Btu/h) and Plis DC load in watts

26、(Btu/h). The DC load is given by(2)where I is the DC load current in amps, Ir is the rated DC load current in amps, and DF is the load diversity factor. The load diversity factor is obtained in the same manner as presented in White et al. (2004b). Given the rated power percent, the percent SMR effic

27、iency, , is found from the SMR efficiency curve; a typical curve is shown in Figure 1 which is based on data provided by Smith (2003). The percent SMR efficiency is given by the ratio of the output power to the input power and is expressed as(3)where Plis SMR output power and PI is the SMR input pow

28、er.The rate of SMR heat loss is the difference between the input power and the output power which is expressed as .(4)By solving equation (3) for PIand substituting the result into equation (4) shows that the SMR heat loss as a function of the load and the efficiency is .(5)The analysis just present

29、ed explains how the SMR power loss spreadsheet of Figure 2 determines the rate of dissipated heat. In Figure 2, six SMRs are connected in parallel and feed a load of 9000 watts (30708 Btu/h) and 48 volts. Each SMR consisted of a 1500 watt (5118 Btu/h), single phase 120 VAC input, and 48 DCV output d

30、evice. The DC load is working at 75% of capacity with a diversity factor of 0.9.During the research of this electrical device, information was obtained from manufacturer literature. In compiling information from eight manufacturers on switched mode recti-fiers, data were collected on more than 170 s

31、eparate devices which showed that the efficiency depends on the load, SMR topologies (ferro resonant, resonant, quasi-resonant, forward, boost topology, and others), nominal AC input voltage, the number of phases, and the nominal DC output voltage.P 100 Pl()Pr()=PlPrDF IIr-= 100 Pl()PI=PlossPIPl=Plo

32、ssPl100-1=2010, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions (2010, Vol. 116, Part 2). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted

33、without ASHRAEs prior written permission.620 ASHRAE TransactionsTable 1. RP-1395 ScopeDevice TypeStatus at Project InitiationNeeded Information Planned Work Scope Project Work ResultsDC Switchgear None.Component loss numbersTypical construction dataSpreadsheet type means of evaluating losses Model a

34、nd test 24 V and 48 V DC sys-tems to calibrate and verify loss calcu-lation by testing 3 switchgear installations.1) Published test information in the technical literature was used to verify published man-ufacture data regarding switch mode rectifiers.2) Spreadsheet created.Medium Voltage Switchgear

35、Spreadsheet type means of evaluating lossesVerification of manufacturer supplied loss data for breakers, bus bars, current transformers, potential transformers, relays, and auxiliary compartmentsInfluence of enclosures on losses.Test losses on 3 switchgear installations to calibrate and verify loss

36、calculation spreadsheet Tested items are to among 5, 7.2, designed to be placed in a cabinet or cutout box placed in or against a wall, partition or other support; and accessible only from the front,” (NEC, Article 100-definitions). Panel-boards differ from switchboards and low-voltage switchgear as

37、 shown in Table 6. The panelboard is designed to handle voltages up to 0.6 kV, to be connected directly to loads, to be mounted against a wall, to be built with a vertical three phase bus bar system, to accom-modate rated currents up to 1200 amps, and to be accessible only from the front. The power

38、panelboard is classified by its current rating which is either 250, 400, 600, 800, or 1200 amps and by its dimensions which consist of height, bus bar length, width, and depth. These dimensions are also used to determine the total number of branch circuits which consist of circuit breakers, fusible

39、switches, and motor starters. All of branch circuits are connected to the vertical main bus. The panelboard enclosures are made of galvanized steel while the vertical main bus is made of copper or aluminum with rectangular cross Figure 6 5/15 kV isolated phase bus bar heat loss spreadsheet.2010, Ame

40、rican Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions (2010, Vol. 116, Part 2). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs pri

41、or written permission.630 ASHRAE TransactionsTable 6. Panelboard Characteristics (Panelboard versus Switchboard and Low Voltage Switchgear(120 V, 208V, and 480 V)Characteristics Panelboard Switchboard Low Voltage SwitchgearFunction orApplicationControl light, heat, or power cir-cuitsLoad distributio

42、n before thepanelboardSubstation application before the switchboardDesignCabinet or cut out box mounted against a wallStand-alone enclosure mounted away from a wall. Construction with inter-nal barriers between devices and bus-ses is optional.Stand-alone enclosure mounted away from a wall. Construct

43、ion with internal barriers between devices and busses. Breakers fullycompartmentalized with barriers.Bus BarsVertical bus bars3 phaseHorizontal and Vertical bus bars3 phase and groundHorizontal and Vertical bus bars3 phaseBreaker Rated Current Up to 1200 amps 150 to 5000 amps 800 to 5000 ampsAccess

44、Only from the front Front and rear access Front and rear accessDisconnect DevicesFusible SwitchMCCBFusible SwitchMCCBICCBLVPCBLVPCBFLVPCBFused low-voltage power circuit breakerFigure 7 0.6 kV5/15 kV nonsegregated bus way heat loss spreadsheet.2010, American Society of Heating, Refrigerating and Air-

45、Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions (2010, Vol. 116, Part 2). For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission.2010 ASHRAE 631sections. T

46、he dimensions and ampacities of the main bus are given by UL 67-1993. In order to develop a loss model for panelboards, attention will be given to MCCB, fusible switch, motor starter, and bus bar with enclosure losses. The assumption of balanced three phase currents is applied to all panelboard devi

47、ces. The loss models of the MCCB, fusible switch and motor starter were shown in previous sections of this paper, and only the bus bar and enclosure losses are treated here. The power losses in bus bars and enclosures were deter-mined by the numerical methods of White and Piesciorovsky (2009) and De

48、l Vecchio (2003). The bus bar and enclosure losses at the 250, 400, 600, 800 and 1200 amps ratings were found and the results were put through a regression analysis. The enclosure-bus bar power loss was found to bewatts (15)where Pbus is the enclosure-bus bar power loss in watts, I is the load curre

49、nt flowing through a single bus bar in amps, Ibusis the current rating of the bus bar in amps, H is the bus bar length in meters, and DF is the load diversity factor applied to the main disconnecting device. Multiplying equation (15) by 3.412 provides the power loss in Btu/h. The main disconnect-ing device load diversity factor is(16)where DFcis the secondary branch device diversity load factor and Icis the secondary branch device current in amps. Equation (16) is not true on an instantaneous basis. Its purpose is to predict the a