NEMA及IEC標準下的電機銘牌識別（連載四）
# 15：功率因數(shù) (PF)
銘牌上的功率因數(shù)有時縮寫為 PF 或 P.F。功率因數(shù)是有功功率 (W) 與視在功率 (VA) 之比，以百分比表示。功率因數(shù)也等于電流與電壓之間滯后角的余弦值 (“Cos”)。
對于感應電機，功率因數(shù)會隨負載而變化?？蛰d時功率因數(shù)最小，隨著電機負載的增加而增加。功率因數(shù)通常在電機滿載或接近滿載時達到峰值。
它的值范圍為0到1，表示滿載狀態(tài)。功率因數(shù)最好接近 1 (100%)?？梢酝ㄟ^添加電容器來提高功率因數(shù)。
在 NEMA 電機中，功率因數(shù)縮寫為“PF”，在 IEC 電機中，功率因數(shù)標記為“Cos”。
# 15: POWER FACTOR (PF)
Power factor on the nameplate is sometimes abbreviated as PF or P.F. Power factor is the ratio of active power (W) to apparent power (VA), expressed as a percentage. The power factor is also equal to the cosine (“Cos”) of the angle formed by the lag between the current with respect to the voltage.
For induction motors, the power factor varies with load. Power factor is minimum at no load and increases as additional load is applied to the motor. Power factor usually reaches a peak at or near full load on the motor.
It can vary from 0 to 1 and is for the full load condition. It is desirable to have high power factors close to unity (100%). The power factor can be improved by adding capacitors.
In NEMA motors the power factor is abbreviated as “PF” and for IEC motors the power factor is tagged as “Cos”.
# 16：服務系數(shù) (SF)
電機服務系數(shù) (SF) 是指電機在正確的電壓容差范圍內(nèi)正常運行時，短時間內(nèi)能夠承受的過載百分比。它非常實用，因為它可以在估算功率需求和實際運行功率要求時提供一些“參考”。它還能降低額定負載下的繞組溫度，防止間歇性溫升，并有助于抵消低電壓或不平衡的線路電壓。例如，開放式防滴 (ODP) 電機的標準服務系數(shù)為1.15。這意味著，一臺10馬力、服務系數(shù)為1.15 的電機，在短期使用時可以提供11.5馬力的功率。一些小功率電機的服務系數(shù)更高，例如1.25、1.35 甚至1.50。
NEMA 將服務系數(shù)定義為一個乘數(shù)，當它應用于額定馬力時，表示在額定電壓和頻率下，在服務系數(shù)規(guī)定的條件下可以承載的允許馬力負載。該服務系數(shù)可用于以下用途：
1. 彌補預測間歇性系統(tǒng)馬力需求的不準確性。
2. 通過降低額定負載下的繞組溫度來延長絕緣壽命。
3. 處理間歇性或偶爾的過載。
4. 允許環(huán)境溫度偶爾高于40°C。
5. 補償?shù)碗妷夯虿黄胶怆娫措妷骸?/p>
然而，NEMA 在討論服務系數(shù)時也增加了一些注意事項：
1. 長時間以服務系數(shù)負載運行通常會降低電機轉速、壽命和效率。
2. 電機可能無法提供足夠的啟動和拉出扭矩，并且啟動器/過載尺寸可能不正確。這反過來會影響電機的整體壽命。
3. 切勿依賴服務系數(shù)來持續(xù)承載負載。
4. 服務系數(shù)是在額定電壓、頻率、環(huán)境溫度和海平面條件下運行而確定的。
大多數(shù)電機的開式電機占空比為1.15，全封閉式電機占空比為1.0。傳統(tǒng)上，全封閉風冷 (TEFC) 電機的服務系數(shù)為1.0，但現(xiàn)在大多數(shù)制造商提供的TEFC 電機的服務系數(shù)為1.15，與ODP 電機相同。大多數(shù)危險場所電機的服務系數(shù)為1.0，但某些用于 I 類應用的專用電機的服務系數(shù)為1.15。
只有當服務系數(shù)高于1.0時，才需要在銘牌上注明。
# 16: SERVICE FACTOR (SF)
Motor Service Factor (SF) is the percentage of overloading the motor can handle for short periods when operating normally within the correct voltage tolerances. This is practical as it gives you some 'fudge' in estimating horsepower needs and actual running horsepower requirements. It also allows for cooler winding temperatures at rated load, protects against intermittent heat rises, and helps to offset low or unbalanced line voltages. For example, the standard SF for open drip-proof (ODP) motors is 1.15. This means that a 10-hp motor with a 1.15 SF could provide 11.5 hp when required for short-term use. Some fractional horsepower motors have higher service factors, such as 1.25, 1.35, and even 1.50.
NEMA defines service factor as a multiplier, when applied to the rated horsepower, indicates a permissible horsepower loading, which may be carried under the conditions specified for the service factor at rated voltage and frequency. This service factor can be used for the following:
1. To accommodate inaccuracy in predicting intermittent system horsepower needs.
2. To lengthen insulation life by lowering the winding temperature at rated load.
3. To handle intermittent or occasional overloads.
4. To allow occasionally for ambient above 40°C.
5. To compensate for low or unbalanced supply voltages.
NEMA does add some cautions, however, when discussing the service factor:
1. Operation at service factor load for extended periods will usually reduce the motor speed, life and efficiency.
2. Motors may not provide adequate starting and pull-out torques, and incorrect starter/overload sizing is possible. This in turn affects the overall life span of the motor.
3. Do not rely on the service factor capability to carry the load on a continuous basis.
4. The service factor was established for operation at rated voltage, frequency, ambient and sea level conditions.
Most motors have a duty factor of 1.15 for open motors and 1.0 for totally closed motors. Traditionally, totally enclosed fan cooled (TEFC) motors had an SF of 1.0, but most manufacturers now offer TEFC motors with service factors of 1.15, the same as on ODP motors. Most hazardous location motors are made with an SF of 1.0, but some specialized units are available for Class I applications with a service factor of 1.15.
The service factor is required to appear on the nameplate only if it is higher than 1.0.
# 17：滿載標稱效率
效率定義為輸出功率與輸入功率之比。電機損耗以熱量的形式存在，包括定子繞組損耗、轉子損耗、鐵芯損耗（磁滯和渦流）、摩擦和風阻以及雜散負載損耗。
NEMA標準MG1-12.54.2提供了確定效率值的說明。該標準規(guī)定，銘牌上顯示的標稱效率不得高于相同設計的大量電機的平均效率。此外，在額定電壓和頻率下運行時，滿載效率不得低于與標稱效率相關的最小值。
在比較不同電機制造商的效率時應謹慎。由于整個行業(yè)沒有統(tǒng)一的標準方法，因此很難基于已發(fā)布、引用或測試數(shù)據(jù)來比較效率。最常參考的標準是IEEE 112（美國）、IEC（國際）、JEC-27（日本）、BS-269（英國）和 ANSI C50.20（與 IEEE 112 相同）。IEEE 112 在美國的應用最為廣泛，同時允許使用多種測試方法。首選的測試程序是IEEE方法B，即電機滿載運行，并直接測量功率。
通常，大型電機的效率高于小型電機。如今，高效三相電機的效率范圍從1馬力時的86.5%到300馬力時的95.8%。銘牌上顯示的效率值是“標稱滿載效率”，該效率值是使用高精度測功機按照 IEEE 標準 112 方法 B 中規(guī)定的程序測定的。標稱效率是指對大量相同電機進行測試并確定該批次電機平均值后所得的平均值。有些電機的效率值可能更高，有些電機的效率值可能更低，但所有測試電機的平均值均顯示為銘牌上的標稱效率值。因此，額定效率 92.1 本質(zhì)上表示這是該電機型號的平均效率，但實際效率可能會有所不同。
任何形式的熱量都會降低效率，包括摩擦、定子繞組損耗、轉子損耗、鐵芯損耗（磁滯和渦流）等。制造商保證電機的實際效率在該標稱效率的某個范圍內(nèi)。效率范圍因制造商而異。NEMA 規(guī)定的最大允許“范圍”為 20%。這是一個很大的范圍；因此，請密切關注制造商的實際最低保證！
# 17: FULL LOAD NOMINAL EFFICIENCY
Efficiency is defined as the ratio of the power output divided by the power input. Machine losses are in the form of heat, and include stator winding loss, rotor loss, core loss (hysteresis and eddy current), friction and windage, and stray load loss.
NEMA standard MG1-12.54.2 provides instructions for establishing the value of efficiency. The standard states that the nominal efficiency shown on the nameplate shall not be greater than the average efficiency of a large population of motors of the same design. Also, the full load efficiency, when operating at rated voltage and frequency, will not be less than the minimum value associated with the nominal value.
Care should be taken in comparing efficiencies from one motor manufacturer to another. It is difficult to compare efficiencies based on published, quoted or test data, due to the fact that there is no single standard method which is used throughout the industry. The most common referred to standards are IEEE 112 (U.S.), IEC (International), JEC-27 (Japanese), BS-269 (British) and ANSI C50.20 (same as IEEE 112). IEEE 112 is used more than any of the others in the United States, while allowing for a variety of test methods to be used. The preferred procedure is IEEE method B, where the motor is operated at full load, and the power is directly measured.
Generally, larger motors will be more efficient than smaller motors. Today's premium efficiency 3-phase motors have efficiencies ranging from 86.5% at 1 hp to 95.8% at 300 hp. The efficiency value that appears on the nameplate is the “nominal full-load efficiency” as determined using a very accurate dynamometer and a procedure described by IEEE Standard 112, Method B. The nominal value is what the average would be if a substantial number of identical motors were tested and the averages of the batch were determined. Some motors might have a higher value and others might be lower, but the average of all units tested is shown as the nominal nameplate value. Thus, essentially the rating Nom Eff. 92.1 means this is an average efficiency of this motor model, but actual efficiency may vary.
The efficiency is reduced by any form of heat, including friction, stator winding loss, rotor loss, core loss (hysteresis and eddy current), etc. The actual motor efficiency is guaranteed to be within a band of this nominal efficiency by the manufacturer. The efficiency band varies from manufacturer to manufacturer. The maximum allowable "band" is 20% set by NEMA. This is a large range; therefore pay close attention to the manufacturer's actual minimum guarantee!
# 18：機座尺寸（可選）
大多數(shù)電機尺寸都已標準化，并根據(jù)機座尺寸編號和字母名稱進行分類。該系統(tǒng)由美國電氣制造商協(xié)會 (NEMA) 開發(fā)，并根據(jù)外殼尺寸、馬力和轉速為標準電機額定值分配特定的機座尺寸。編號描述了安裝尺寸，包括底孔安裝方式、軸徑、軸高等。但是，它并未定義電機總長度和高度、接線盒延伸長度等。
目前，整馬力異步電機的標準化機座尺寸范圍為143T至445T。這些標準涵蓋了功率在100至200馬力范圍內(nèi)的大多數(shù)電機。
用于表示機座尺寸的數(shù)字根據(jù)電機的物理尺寸具有特定含義。前兩位數(shù)字與電機軸高有關，其余一位或多位數(shù)字與電機長度有關。根據(jù)經(jīng)驗，可以通過將機座尺寸的前兩位數(shù)字除以 4 來計算臥式電機的軸高（以英寸為單位，“D”尺寸）。請注意，這適用于所有143T至445T機架尺寸的底座式 NEMA 機架電機。
機架尺寸的第三位數(shù)字與電機長度有關，但并沒有簡單易行的經(jīng)驗法則。
需要注意的是，當標準底座式電機的機架尺寸僅在第三位數(shù)字上有所不同時，軸直徑、軸長度以及從軸端到電機軸端底座螺栓孔的距離將相同。
以上示例中的長度差異發(fā)生在尺寸A和B所示的底座之間。后綴 T 表示電機機架分配符合現(xiàn)行標準，即所謂的“T”機架“Nu-Rate”標準，該標準于1964年采用。
請注意，機架尺寸僅指安裝尺寸，與電機殼體直徑無直接關系。通常，隨著機架號的增加，電機的物理尺寸和馬力也會增加。很多相同馬力的電機都采用不同的機座號。
使用公制電機（IEC 型）時，其概念與上述相同，但有一點不同：現(xiàn)在軸距底座的高度以毫米而非英寸表示。機座號指的是軸距底座的高度，以毫米為單位。（詳情將在本文的后面部分進一步介紹）。
一些常見的機座號示例包括：
代碼 | 定義 |
C | NEMA C 型端面安裝（指定是否帶剛性底座） |
D | NEMA D 型法蘭安裝（指定是否帶剛性底座） |
H | 表示帶剛性底座的機座，其 F 尺寸大于不帶后綴 H 的相同機座。例如，56H 型機座電機組合具有 NEMA 56 和 NEMA 143-5T 的安裝孔以及標準 NEMA 56 軸。 |
J | NEMA C 型端面螺紋軸泵電機 |
JM | 具有特定尺寸和軸承的直聯(lián)泵電機 |
JP | 具有特定尺寸和軸承的直聯(lián)泵電機 |
M | 6 3/4 英寸法蘭（燃油燃燒器） |
N | 7 1/4 英寸法蘭（燃油燃燒器） |
T, TS | 如果“T”或“TS”后沒有其他字母，則為 NEMA 標準整馬力軸尺寸。 |
TS | 用于皮帶傳動負載的 NEMA 標準“短軸”電機 |
Y | 非 NEMA 標準安裝；需要圖紙確定尺寸。可以指定特殊底座、端面或法蘭。 |
Z | 非 NEMA 標準軸；需要圖紙來確定尺寸。 |
有關更多標準名稱，請參閱 NEMA MG 1-11.01。
# 18: FRAME SIZE (optional)
Most motor dimensions are standardized and categorized by a frame size number and letter designation. This system was developed by NEMA and specific frame sizes have been assigned to standard motor ratings based on enclosure, horsepower and speed. The number describes the mounting dimensions, including foot hole mounting pattern, shaft diameter, shaft height, etc. However, it does not define overall length and height, conduit box extension length, etc.
The current standardized frames for integral horsepower induction motors ranges from 143T to 445T. These standards cover most motors in the range of one through two hundred horsepower.
The numbers used to designate frame sizes have specific meanings based on the physical size of the motor. The first two digits are related to the motor shaft height and the remaining digit or digits relate to the length of the motor. As a rule of thumb, you can calculate the shaft height on horizontal motors in inches, (“D” dimension), by dividing the first two digits of the frame size by four. Please note that this works on all foot-mounted NEMA frame motors in 143T through 445T frames.
The third digit of the frame size is related to the length of the motor but there is no rule of thumb that can be easily applied.
It is important to note that when standard foot-mounted motors have frame sizes that differ only in the third digit, the shaft diameters, shaft lengths, and distance from the end of the shaft to the bolt holes in the feet on the shaft end of the motor will be the same.
The length difference in the examples above occurs between the feet as shown by dimensions A and B. The suffix T indicates that the motor frame assignment conforms to the current, or so called “T” frame “Nu-Rate” standards which were adopted in 1964.
Note that the frame size refers to mounting only and has no direct bearing on the motor body diameter. In general, as a frame number becomes higher, so does the physical size of the motor and the horsepower. There are many motors of the same horsepower built in different frames.
When working with metric motors (IEC type), the concept is the same as noted above with one exception: the shaft height above the base is now noted in millimeters rather than inches. The frame size is the shaft height in millimeters. (The details are further described later in the course).
Some common frame examples include:
Number | Definition |
C | NEMA C face mounting (specify with or without rigid base) |
D | NEMA D flange mounting (specify with or without rigid base) |
H | Indicates a frame with rigid base having an F dimension larger than that of the same frame without the suffix H. For example, combinations of 56H base motors have mounting holes for NEMA 56 and NEMA 143-5T and a standard NEMA 56 shaft. |
J | NEMA C face, threaded shaft pump motor |
JM | Close-coupled pump motor with specific dimensions and bearings |
JP | Closed-coupled pump motor with specific dimensions and bearings |
M | 6 3/4" flange (oil burner) |
N | 7 1/4" flange (oil burner) |
T, TS | Integral horsepower NEMA standard shaft dimensions if no additional letters follow the "T" or "TS." |
TS | Motor with NEMA standard "short shaft" for belt driven loads |
Y | Non-NEMA standard mount; a drawing is required to be sure of dimensions. Can indicate a special base, face or flange. |
Z | Non-NEMA standard shaft; a drawing is required to be sure of dimensions. |
For further standard designations refer to NEMA MG 1- 11.01.
# 19：NEMA 設計字母
電機繞組和轉子設計的變化會改變感應電機的性能特性。為了在應用中保持一致性，NEMA 指定了通用電機的特定設計，這些電機具有特定的堵轉轉矩、極限轉矩、轉差率、啟動電流或其他值。A、B、C 和 D 設計有標準定義。字母名稱描述了電機的轉矩和電流特性。
NEMA A 型電機 具有正常的啟動轉矩，但啟動電流較大。這適用于短時間重載的應用。注塑機是此類電機的理想應用。
NEMA B 型電機 具有正常的啟動轉矩和較低的啟動電流。這些電機是應用最廣泛的設計，其堵轉轉矩足以啟動各種工業(yè)機械，并且堵轉啟動電流也適用于大多數(shù)電力系統(tǒng)。B 設計的一些應用包括機床、風扇和鼓風機、壓縮機、削片機和離心泵。這些是最常見的電機類型。
NEMA C 型電機 具有高啟動扭矩（約225%）和低啟動電流。這些電機具有高堵轉扭矩和相對較高的滿載滑差。由于其高堵轉扭矩和高滿載滑差，它們特別適合啟動重載，例如往復式壓縮機、加煤機、破碎機和磨粉機，以及容積泵。
NEMA D 型電機 具有高啟動扭矩和低啟動電流，但滑差較大?？蛰d時，電機以較小的滑差運行。當施加峰值負載時，電機滑差會顯著增加，從而使設備能夠吸收能量。這降低了電氣系統(tǒng)提供的功率峰值，從而使功率需求更加均衡。這些電機可用于帶有重型飛輪的低速沖床或起重應用。
# 19: NEMA DESIGN LETTER
Changes in motor windings and rotor design will alter the performance characteristics of induction motors. To obtain uniformity in application, NEMA has designated specific designs of general purpose motors having specified locked rotor torque, breakdown torque, slip, starting current, or other values. There are standard definitions for designs A, B, C and D. The letter designation describes the torque and current characteristics of the motor.
NEMA Design A motors have normal starting torques, but high starting currents. This is useful for applications with brief heavy overloads. Injection molding machines are a good application for this type of motor.
NEMA Design B motors have normal starting torque, with low starting current. These are the most widely used design, and have locked rotor torques adequate for starting a wide variety of industrial machines and locked rotor starting currents acceptable to most power systems. Some Design B applications would include machine tools, fans and blowers, compressors, chippers, and centrifugal pumps. These are the most common type of motors.
NEMA Design C motors have high starting torque (approximately 225%) and low starting current. These motors have high locked rotor torque and relatively high full load slip. They are especially suited for starting heavy loads such as reciprocating compressors, stokers, crushers and pulverizers, as well as positive displacement pumps due to their high locked rotor torques and high full load slip.
NEMA Design D motors have high starting torque and low starting current, but with high slip. At no load the motor operates with little slip. When peak load is applied, the motor slip increases appreciably, allowing the unit to absorb the energy. This reduces power peaks supplied by the electrical system, resulting in a more uniform power requirement. These motors may be used on applications like a low speed punch press with a heavy flywheel, or hoisting applications.
# 20：機殼類型
電機機殼必須保護繞組、軸承和其他機械部件免受潮濕、化學物質(zhì)、機械損壞和砂礫磨損的影響。NEMA 標準 MG1-1.25 至 1.27 定義了 20 多種機殼類型，涵蓋開放式電機、全封閉式電機以及帶封裝或密封繞組的電機。最常見的機殼類型包括：
開放式防滴漏 (ODP)：允許空氣在繞組中循環(huán)冷卻，但防止液滴在與垂直方向成 15 度角的范圍內(nèi)滴入電機。通常用于相對清潔干燥的室內(nèi)應用。
全封閉風扇冷卻式 (TEFC)：阻止機架內(nèi)外空氣自由交換，但不完全密封機架。風扇安裝在軸上，在運行過程中將空氣推過機架，以幫助冷卻。肋狀機架的設計旨在增加冷卻表面積。 TEFC 型機殼是所有機殼中用途最廣泛的一種。它適用于泵、風扇、壓縮機、通用工業(yè)皮帶傳動裝置和直接連接設備。
全封閉無通風 (TENV)：與 TEFC 類似，但沒有冷卻風扇，依靠對流冷卻。無通風口，緊密封閉以防止空氣自由交換，但不密封。這類機殼適用于暴露于灰塵或潮濕環(huán)境中，但不適用于非常潮濕或危險（爆炸性）場所。
全封閉風冷 (TEAO)：專為軸裝風扇或皮帶驅(qū)動風扇設計的防塵風扇和鼓風機電機。電機必須安裝在風扇氣流范圍內(nèi)。
全封閉沖洗電機 (TEWD)：設計用于承受高壓沖洗或其他高濕度或潮濕環(huán)境。適用于 TEAO、TEFC 和 TENV 型機殼。
全封閉、惡劣及惡劣環(huán)境電機：設計用于極度潮濕或化學環(huán)境，但不適用于危險場所。
防爆外殼 (EXPL)：防爆電機是一種全封閉的機器，旨在承受電機外殼內(nèi)特定氣體或蒸汽的爆炸，并防止電機外部因火花、閃光或爆炸而著火。這些電機專為特定危險用途而設計，例如含有氣體或危險粉塵的環(huán)境。為了安全運行，電機的最高工作溫度必須低于周圍氣體或蒸汽的燃點。防爆電機的設計、制造和測試均符合美國保險商實驗室 (UL) 的嚴格要求。
危險場所 (HAZ)：危險場所電機應用根據(jù)存在的危險環(huán)境類型、造成危險的特定材料的特性、暴露于環(huán)境中的可能性以及對造成危險的物質(zhì)而言被認為安全的最高溫度水平進行分類。
定義此信息的格式是國家電氣規(guī)范 (NFPA-70) 定義的類別、組別、分類和溫度代碼結構。危險場所定義如下：
1) I 類
? A 組：乙炔
? B 組：丁二烯、環(huán)氧乙烷、氫氣、環(huán)氧丙烷以及氫氣含量超過 30% 的人造氣體。
? C 組：乙醛、環(huán)丙烷、乙醚、乙烯。
? D 組：丙酮、丙烯腈、氨、苯、丁烷、乙醇、二氯乙烷、汽油、己烷、異戊二烯、甲烷（天然氣）、甲醇、石腦油、丙烷、丙烯、苯乙烯、甲苯、醋酸乙烯酯、氯乙烯、二甲苯。
2) II 類
? E 組：鋁、鎂及其他具有類似特性的金屬粉塵。
? F 組：炭黑、焦炭或煤塵。
? G 組：面粉、淀粉或谷物粉塵。
3) III 類
? 易燃纖維，例如人造絲、棉、劍麻、大麻、可可纖維、麻絮、細木工板以及其他類似性質(zhì)的材料。
NEMA外殼描述與IEC防護等級 (IP) 代碼類似。NEMA名稱更具描述性和通用性，而 IEC IP 代碼則更精確，采用兩位數(shù)代碼進行嚴格定義，第一位數(shù)字表示電機對固體物體的防護程度，第二位數(shù)字表示電機對濕氣的防護程度。例如，NEMA“開放式防滴 (ODP)”電機對應 IP22，NEMA“全封閉”電機對應IP54，NEMA“防風雨”電機對應IP45，NEMA“耐沖洗”電機對應IP55。
# 20: ENCLOSURE TYPE
The enclosure of the motor must protect the windings, bearings, and other mechanical parts from moisture, chemicals, mechanical damage and abrasion from grit. NEMA standards MG1- 1.25 through 1.27 define more than 20 types of enclosures under the categories of open machines, totally enclosed machines, and machines with encapsulated or sealed windings. The most common types of enclosures are:
Open Drip Proof (ODP): Allows air to circulate through the windings for cooling, but prevent drops of liquid from falling into motor within a 15 degree angle from vertical. Typically used for indoor applications in relatively clean, dry locations.
Totally Enclosed Fan Cooled (TEFC): Prevents the free exchange of air between the inside and outside of the frame, but does not make the frame completely airtight. A fan is attached to the shaft and pushes air over the frame during its operation to help in the cooling process. The ribbed frame is designed to increase the surface area for cooling purposes. The TEFC style enclosure is the most versatile of all. It is used on pumps, fans, compressors, general industrial belt drive and direct connected equipment.
Totally Enclosed Non-Ventilated (TENV): Similar to a TEFC, but has no cooling fan and relies on convection for cooling. No vent openings, tightly enclosed to prevent the free exchange of air, but not airtight. These are suitable for uses which are exposed to dirt or dampness, but not very moist or hazardous (explosive) locations.
Totally Enclosed Air Over (TEAO): Dust-tight fan and blower duty motors designed for shaft mounted fans or belt driven fans. The motor must be mounted within the airflow of the fan.
Totally Enclosed Wash down (TEWD): Designed to withstand high pressure wash-downs or other high humidity or wet environments. Available on TEAO, TEFC and TENV enclosures.
Totally enclosed, hostile and severe environment motors: Designed for use in extremely moist or chemical environments, but not for hazardous locations.
Explosion-proof enclosures (EXPL): The explosion proof motor is a totally enclosed machine and is designed to withstand an explosion of specified gas or vapor inside the motor casing and prevent the ignition outside the motor by sparks, flashing or explosion. These motors are designed for specific hazardous purposes, such as atmospheres containing gases or hazardous dusts. For safe operation, the maximum motor operating temperature must be below the ignition temperature of surrounding gases or vapors. Explosion proof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories.
Hazardous Location (HAZ): Hazardous location motor applications are classified by the type of hazardous environment present, the characteristics of the specific material creating the hazard, the probability of exposure to the environment, and the maximum temperature level that is considered safe for the substance creating the hazard.
The format used to define this information is a class, group, division and temperature code structure as defined by the National Electric Code (NFPA-70). The following hazardous locations are defined:
1) CLASS I
? Group A: Acetylene
? Group B: Butadiene, ethylene oxide, hydrogen, propylene oxide, manufactured gases containing more than 30% hydrogen by volume.
? Group C: Acetaldehyde, cyclopropane, diethyl ether, ethylene.
? Group D: Acetone, acrylonitrile, ammonia, benzene, butane, ethanol, ethylene dichloride, gasoline, hexane, isoprene, methane (natural gas), methanol, naphtha, propane, propylene, styrene, toluene, vinyl acetate, vinyl chloride, xylene.
2) CLASS II
? Group E: Aluminum, magnesium, and other metal dusts with similar characteristics.
? Group F: Carbon black, coke or coal dust.
? Group G: Flour, starch or grain dust.
3) CLASS III
? Easily ignitable fibers, such as rayon, cotton, sisal, hemp, cocoa fiber, oakum, excelsior and other materials of similar nature.
The NEMA enclosure description is similar to the IEC Index of Protection (IP) code. The NEMA designations are more descriptive and general, whereas the IEC IP codes are more precise and narrowly defined by a 2-digit code, with the first digit defining how well protected the motor is from solid objects and the second digit describing how well protected the motor is from moisture. For example, a NEMA "Open Drip Proof (ODP)" motor corresponds to an IP22 and a NEMA "Totally Enclosed" motor corresponds to an IP54, a NEMA "Weather-Proof" motor to an IP45, and a NEMA "Wash-Down" motor to an IP55.
# 21：熱保護
熱保護是指電機的過熱保護功能（如有配備）。熱保護包括以下幾種：
自動（自動復位）：包含溫度傳感裝置，如果因啟動失敗或過載導致溫度過高，該裝置會斷開電源的一側。電機冷卻后，熱保護器會自動恢復供電。請勿在意外重啟可能造成危險的場合使用。
阻抗（阻抗）：根據(jù) UL 標準 No. 519，電機設計使其在堵轉（失速）情況下不會在 15 天內(nèi)燒壞。
手動（手動復位）：包含溫度傳感裝置，如果因啟動失敗或過載導致溫度過高，該裝置會斷開電源的一側。電機冷卻后，必須按下外部按鈕才能恢復供電。嘗試復位電機保護器前，請先關閉電源。在意外重啟可能造成危險的場合，例如鋸子、傳送帶、壓縮機等，優(yōu)先選擇這種裝置。
無：電機不包含溫度傳感器，用于防止電機因啟動失敗或過載而過熱。電機應根據(jù) NEC 和當?shù)匾?guī)范要求采用其他保護措施。
T-St（溫控器）：安裝在電機內(nèi)部的溫度傳感器，并引出單獨的導線連接到電機啟動器先導電路。在啟動失敗或過載情況下，溫控器觸點將斷開。電機冷卻后，溫控器觸點將自動重新閉合。
# 21: THERMAL PROTECTION
Thermal protection describes the motor’s over temperature protection, if so equipped. Thermal protection can include the following:
Auto (Automatic Reset): Contains temperature-sensing device that disconnects one leg of its power source if temperature becomes excessive due to failure-to-start or overload. After motor cools, thermal protector automatically restores power. Should not be used where unexpected re-starting would be hazardous
Imp (Impedance): Motor is designed so that it will not burn out in less than 15 days under locked rotor (stalled) conditions, in accordance with UL standard No. 519.
Man (Manual Reset): Contains a temperature-sensing device that disconnects one leg of its power source if temperature becomes excessive due to failure-to-start or overload. After motor cools, an external button must be pushed to restore power to the motor. Turn off power prior to attempting to reset motor protector. Preferred where unexpected re-starting would be hazardous, as on saws, conveyors, compressors, etc
None: Motor contains no temperature-sensing device to protect motor from excessive temperature due to failure-to-start or overload. Motor should be protected by other means in accordance with the NEC and local code requirements.
T-St (Thermostat): A temperature-sensing device installed inside the motor with separate leads brought out for connection into motor starter pilot circuit. Under failure-to-start or overload conditions, thermostat contacts will open. Thermostat contacts will reclose automatically when motor cools.
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