IPS21-35AD 3BHB017688R0001工业卡件,DCS模块卡件
式中：Ieq=等效电机加热电流Iper_unit=基于FLA的每单位电流I2=负序电流I1=正序电流k=常数下图显示了NEMA（美国国家电气制造商协会）建议的电机降额，作为电压不平衡的函数。假设典型的感应电机具有6 x FLA的浪涌和0.167的负序阻抗，电压不平衡为1、2、3、4和5%，电流不平衡分别为6、12、18、24和30%。基于这一假设，GE电力管理曲线说明了为不平衡偏置k系数设定值输入的不同k值的电机降额。注意，当k=8时创建的曲线几乎与NEMA降额曲线相同。图4-16：电压不平衡导致的中等电机减额因数如果输入k值为0，则不平衡偏置将失效，过载曲线将根据测量的每单位电机电流超时。k可以保守计算（典型估计值）（保守估计值），其中ILR是每单位锁定转子电流GE Power Management 469电机管理继电器4-43 4设定值编程4.6 S5热模型4 4.6.5电机冷却当电机电流低于过载拾取设定值时，使用的热容量值呈指数下降。这种减少模拟了电机冷却。应输入停止和运行情况下的电机冷却时间常数。由于冷却是指数级的，时间常数是从100%热容量到0%的总时间的五分之一。停止的电机通常比运行的电机冷却得慢得多。电机冷却计算如下：TCused=使用的热容量TCused_start=过载条件导致的TCused值TCused_end=电机运行时热/冷曲线比率（电机停止时为0）决定的TCuseed值t=时间（分钟）τ=冷却时间常数（运行或停止）Ieq=等效电机加热电流过载_pickup=过载拾取设定点为FLA时间（以分钟为单位）热容量使用冷却时间常数=15分钟TCused_start=85%热/冷比率=80%Ieq/过载TCused_start=85%热时间/冷时间（以分为单位）冷容量使用冷却温度常数=30分钟TCused_start=85%冷/热比率=80%电机在运行额定负载后停止TCused_Time in Minutes热热模型冷却，80%负载热模型冷却，电机停止热模型冷却、100%负载热模型制冷，电机跳闸4-44 469电机管理继电器GE电源管理
where: Ieq = equivalent motor heating current Iper_unit = per unit current based on FLA I2= negative sequence current I1= positive sequence current k = constant The figure below shows recommended motor derating as a function of voltage unbalance recommended by NEMA (the National Electrical Manufacturers Association). Assuming a typical induction motor with an inrush of 6 x FLA and a negative sequence impedance of 0.167, voltage unbalances of 1, 2, 3, 4, and 5% equal current unbalances of 6, 12, 18, 24, and 30% respectively. Based on this assumption, the GE Power Management curve illustrates the motor derating for different values of k entered for the UNBALANCE BIAS K FACTOR setpoint. Note that the curve created when k = 8 is almost identical to the NEMA derating curve. Figure 4–16: MEDIUM MOTOR DERATING FACTOR DUE TO UNBALANCED VOLTAGE If a k value of 0 is entered, the unbalance biasing is defeated and the overload curve will time out against the measured per unit motor current. k may be calculated conservatively (typical estimate) (conservative estimate), where ILR is the per unit locked rotor current GE Power Management 469 Motor Management Relay 4-43 4 SETPOINT PROGRAMMING 4.6 S5 THERMAL MODEL 4 4.6.5 MOTOR COOLING The thermal capacity used value decreases exponentially when the motor current is below the OVERLOAD PICKUP setpoint. This reduction simulates motor cooling. The motor cooling time constants should be entered for both stopped and running cases. Since the cooling is exponential, the time constants are one-fifth of the total time to go from 100% thermal capacity used to 0%. A stopped motor normally cools significantly slower than a running motor. Motor cooling is calculated as follows: where: TCused = thermal capacity used TCused_start = TCused value caused by overload condition TCused_end = TCused value dictated by the hot/cold curve ratio when the motor is running (= 0 when the motor is stopped) t = time in minutes τ = Cool Time Constant (running or stopped) Ieq = equivalent motor heating current overload_pickup= overload pickup setpoint as a multiple of FLA Time in Minutes Thermal Capacity Used Cool Time Constant= 15 min TCused_start= 85% Hot/Cold Ratio= 80% Ieq/Overload TCused_start= 85% Hot/Cold Time in Minutes Thermal Capacity Used Cool Time Constant= 30 min TCused_start= 85% Hot/Cold Ratio= 80% Motor Stopped after running Rated Load TCused Time in Minutes Thermal Thermal Model Cooling, 80% Load Thermal Model Cooling, Motor Stopped Thermal Model Cooling, 100% Load Thermal Model Cooling, Motor Tripped 4-44 469 Motor Management Relay GE Power Management
