ICS TRIPLEX T8151模擬量輸入模塊
電機保護熱模型的目標是：熱保護電機（轉子和定子），而不影響電機的正常和預期運行條件。469熱模型提供了集成的轉子和定子加熱保護。如果冷卻時間常數與電機數據一起提供，則應使用它們。由于轉子和定子加熱和冷卻集成在一個模型中，因此使用較長的冷卻時間常數（轉子或定子）。但是，如果沒有提供冷卻時間常數，則必須確定設置。在確定冷卻時間常數設置之前，應考慮電機的占空比。如果電機通常在沒有過載負荷要求的情況下啟動并連續運行很長時間，則冷卻時間常數可能很大。這將使熱模型變得保守。如果電機的正常占空比涉及頻繁啟動和停止，且具有周期性過載占空比要求，則冷卻時間常數需要更短，更接近電機的實際熱極限。通常情況下，電機在啟動過程中受到轉子限制。因此，定子中的RTD不能提供確定冷卻時間的最佳方法。運行和停止冷卻時間常數的合理設置的確定可以按優先順序列出的以下方式之一完成。電機運行和停止冷卻時間或常數可在電機數據表上提供，或由制造商提供（如有要求）。記住，冷卻是指數的，時間常數是從100%熱容量到0%的總時間的五分之一。嘗試根據電機上的可用數據確定保守值。有關詳細信息，請參見以下示例。如果沒有可用的數據，則必須進行有根據的猜測。也許可以從具有類似尺寸或用途的其他電機估算電機數據。注意，在更好地理解電機要求之前，保守保護最好作為首選。請記住，目標是在不妨礙所需工作負載的情況下保護電機。C、 1.2示例電機數據表表明，允許的啟動順序為2冷或1熱，之后必須等待5小時才能嘗試再次啟動。?這意味著在正常啟動條件下，電機使用的熱容量介于34%和50%之間。因此，允許連續啟動兩次，但不能連續啟動三次。?如果熱/冷曲線或熱/冷安全失速比不可用，則將0.5（1熱/2冷啟動）編程為熱/冷比。?編程啟動抑制“開啟”可在62.5%（50×1.25）熱容量可用時立即重啟。?在2次冷啟動或1次熱啟動后，將使用接近100%的熱容量。使用的熱容量呈指數衰減（計算見第4–43頁第4.6.5節：電機冷卻）。在1個時間常數后，僅使用37%的熱容量，這意味著有足夠的熱容量用于另一次啟動。
goal of the motor protection thermal modeling is: to thermally protect the motor (rotor and stator) without impeding the normal and expected operating conditions that the motor will be subject to. The 469 thermal model provides integrated rotor and stator heating protection. If cooling time constants are supplied with the motor data they should be used. Since the rotor and stator heating and cooling is integrated into a single model, use the longer of the cooling time constants (rotor or stator). If however, no cooling time constants are provided, settings will have to be determined. Before determining the cool time constant settings, the duty cycle of the motor should be considered. If the motor is typically started up and run continuously for very long periods of time with no overload duty requirements, the cooling time constants can be large. This would make the thermal model conservative. If the normal duty cycle of the motor involves frequent starts and stops with a periodic overload duty requirement, the cooling time constants will need to be shorter and closer to the actual thermal limit of the motor. Normally motors are rotor limited during starting. Thus RTDs in the stator do not provide the best method of determining cool times. Determination of reasonable settings for the running and stopped cool time constants can be accomplished in one of the following manners listed in order of preference. The motor running and stopped cool times or constants may be provided on the motor data sheets or by the manufacturer if requested. Remember that the cooling is exponential and the time constants are one fifth the total time to go from 100% thermal capacity used to 0%. Attempt to determine a conservative value from available data on the motor. See the following example for details. If no data is available an educated guess must be made. Perhaps the motor data could be estimated from other motors of a similar size or use. Note that conservative protection is better as a first choice until a better understanding of the motor requirements is developed. Remember that the goal is to protect the motor without impeding the operating duty that is desired. C.1.2 EXAMPLE Motor data sheets state that the starting sequence allowed is 2 cold or 1 hot after which you must wait 5 hours before attempting another start. ? This implies that under a normal start condition the motor is using between 34 and 50% thermal capacity. Hence, two consecutive starts are allowed, but not three. ? If the hot and cold curves or a hot/cold safe stall ratio are not available program 0.5 (1 hot / 2 cold starts) in as the hot/cold ratio. ? Programming Start Inhibit ‘On’ makes a restart possible as soon as 62.5% (50 × 1.25) thermal capacity is available. ? After 2 cold or 1 hot start, close to 100% thermal capacity will be used. Thermal capacity used decays exponentially (see Section 4.6.5: MOTOR COOLING on page 4–43 for calculation). There will be only 37% thermal capacity used after 1 time constant which means there is enough thermal capacity available for another start.
