IS200ACLEH1A机械设备卡件,DCS卡件
过载曲线功能是为保护这些类型的电机而定制的。在电机启动期间持续监测电压，并相应调整加速热极限曲线。电压相关过载曲线由失速或锁定转子状态、加速度和运行过载确定的三种热极限曲线特征形状组成。通过输入运行过载保护曲线的自定义曲线形状来构建曲线。接下来，必须根据最小允许线路电压定义的最小允许启动电压，在与自定义曲线相交的点处为加速度保护曲线输入一个点。还必须输入该电压的锁定转子电流和安全失速时间。必须输入100%线路电压的第二个交点。再次，必须输入锁定转子电流和安全失速时间，这一次是100%线路电压。根据最小允许线路电压和100%线路电压之间的测量线路电压，从安全失速时间和交叉点创建的保护曲线将是动态的。这种保护方法与阻抗继电器一样，固有地考虑了电机速度的变化。阻抗的变化由电机端子电压和线路电流反映。对于任何给定的速度和任何给定的线路电压，只有一个线路电流值。示例：为了说明电压相关过载曲线特性，将使用图4–10：高惯性负载的热极限的热极限。1.构建运行过载热极限的自定义曲线。如果曲线未延伸至加速热极限，则将其延伸，使曲线与加速热极限曲线相交（参见第4–37页图4–11：电压相关过载（自定义曲线））。2.输入加速度过载曲线与80%线路电压的自定义曲线相交的单位电流值。同时输入80%线路电压的单位电流和安全失速保护时间（参见第4–38页图4–12：电压相关过载（加速曲线））。3.输入100%V时的每单位加速度热限值4-锁定转子热限值5-电机加速度曲线对于高于所述电压的值，469将安全失速保护曲线外推至110%电压。该电流水平通过取100%电压下的锁定转子电流并乘以1.10来计算。对于超过110%电流水平的跳闸时间，将使用110%的跳闸时间。（见下图）。
Overload Curve feature is tailored to protect these types of motors. Voltage is continually monitored during motor starting and the acceleration thermal limit curve is adjusted accordingly. The Voltage Dependent Overload Curve is comprised of the three characteristic shapes of thermal limit curves as determined by the stall or locked rotor condition, acceleration, and running overload. The curve is constructed by entering a custom curve shape for the running overload protection curve. Next, a point must be entered for the acceleration protection curve at the point of intersection with the custom curve, based on the minimum allowable starting voltage as defined by the minimum allowable line voltage. The locked rotor current and safe stall time must also be entered for that voltage. A second point of intersection must be entered for 100% line voltage. Once again, the locked rotor current and the safe stall time must be entered, this time for 100% line voltage. The protection curve created from the safe stall time and intersection point will be dynamic based on the measured line voltage between the minimum allowable line voltage and the 100% line voltage. This method of protection inherently accounts for the change in motor speed as an impedance relay would. The change in impedance is reflected by motor terminal voltage and line current. For any given speed at any given line voltage, there is only one value of line current. EXAMPLE: To illustrate the Voltage Dependent Overload Curve feature, the thermal limits of Figure 4–10: THERMAL LIMITS FOR HIGH INERTIAL LOAD will be used. 1. Construct a custom curve for the running overload thermal limit. If the curve does not extend to the acceleration thermal limits, extend it such that the curve intersects the acceleration thermal limit curves (see Figure 4–11: VOLTAGE DEPENDENT OVERLOAD (CUSTOM CURVE) on page 4–37). 2. Enter the per unit current value for the acceleration overload curve intersect with the custom curve for 80% line voltage. Also enter the per unit current and safe stall protection time for 80% line voltage (see Figure 4–12: VOLTAGE DEPENDENT OVERLOAD (ACCELERATION CURVES) on page 4–38). 3. Enter the per unit leration Thermal Limit @ 100%V 4- Locked Rotor Thermal Limit 5- Motor Acceleration Curve For values above the voltage in question, the 469 extrapolates the safe stall protection curve to 110% voltage. This current level is calculated by taking the locked rotor current @ 100% voltage and multiplying by 1.10. For trip times above the 110% current level, the trip time of 110% will be used. (see figure below).
