ICS TRIPLEX T8151模拟量输入模块
电机保护热模型的目标是：热保护电机（转子和定子），而不影响电机的正常和预期运行条件。469热模型提供了集成的转子和定子加热保护。如果冷却时间常数与电机数据一起提供，则应使用它们。由于转子和定子加热和冷却集成在一个模型中，因此使用较长的冷却时间常数（转子或定子）。但是，如果没有提供冷却时间常数，则必须确定设置。在确定冷却时间常数设置之前，应考虑电机的占空比。如果电机通常在没有过载负荷要求的情况下启动并连续运行很长时间，则冷却时间常数可能很大。这将使热模型变得保守。如果电机的正常占空比涉及频繁启动和停止，且具有周期性过载占空比要求，则冷却时间常数需要更短，更接近电机的实际热极限。通常情况下，电机在启动过程中受到转子限制。因此，定子中的RTD不能提供确定冷却时间的最佳方法。运行和停止冷却时间常数的合理设置的确定可以按优先顺序列出的以下方式之一完成。电机运行和停止冷却时间或常数可在电机数据表上提供，或由制造商提供（如有要求）。记住，冷却是指数的，时间常数是从100%热容量到0%的总时间的五分之一。尝试根据电机上的可用数据确定保守值。有关详细信息，请参见以下示例。如果没有可用的数据，则必须进行有根据的猜测。也许可以从具有类似尺寸或用途的其他电机估算电机数据。注意，在更好地理解电机要求之前，保守保护最好作为首选。请记住，目标是在不妨碍所需工作负载的情况下保护电机。C、 1.2示例电机数据表表明，允许的启动顺序为2冷或1热，之后必须等待5小时才能尝试再次启动。•这意味着在正常启动条件下，电机使用的热容量介于34%和50%之间。因此，允许连续启动两次，但不能连续启动三次。•如果热/冷曲线或热/冷安全失速比不可用，则将0.5（1热/2冷启动）编程为热/冷比。•编程启动抑制“开启”可在62.5%（50×1.25）热容量可用时立即重启。•在2次冷启动或1次热启动后，将使用接近100%的热容量。使用的热容量呈指数衰减（计算见第4–43页第4.6.5节：电机冷却）。在1个时间常数后，仅使用37%的热容量，这意味着有足够的热容量用于另一次启动。
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.
