Method for increasing power of a steel rolling system

Most steel mills in medium-sized steel mills are dragged by induction motors with flywheels. At present, in China, some transmission systems are controlled by frequency-sensitive varistors for slip adjustment. Since the load range of rolling mills is very wide, the power factor of the motor is low, and the mechanical properties are soft, so that the utilization of the motor is not fully realized. use.
HC series slip speed-adjusting force adding device consists of starting frequency sensitive rheostat, adjusting resistance box and control system. It overcomes the disadvantages of low sensitivity of frequency sensitive slip adjustment, high water resistance failure rate and large maintenance. The function of motor forcing can be successfully achieved.
The control core adopts Siemens PLC with high control precision and complete functions. Resistor switching adopts thyristor control, accurate and reliable, no noise.
Resistance box uses metal resistors. The advantages of induction motor rotor string resistance are:
(1) Appropriate resistance is beneficial for improving the rotor power factor and increasing the operating torque. Due to the heavy load of the rolling mill with flywheel drive, the motor must operate with maximum capacity, which requires that the rotor power factor must be high. After the induction motor has a series of 5-10% rated resistance in the rotor, the rotor power factor can be close to 1.0. The effect is that the current generated by the rotor can be completely converted into torque, which means that the conversion efficiency is 100%. This is very desirable. On the other hand, using a frequency-sensitive rheostat to start the motor, the inrush current is large, and this part of the resistor is very beneficial to improve the starting conditions;
(2) Increase rotor resistance to reduce stator side losses. The formula ΔP1=ΔP2r1/r2 is the inverse of the stator-side loss and the rotor-side resistance. Therefore, rotor resistance is an energy-consuming element on the rotor side, but it is a useful parameter for the stator side.
(3) When the motor is running, the external resistance of the rotor will inevitably lose part of the energy, especially the loss of the deep-speed control system is quite large, and it should be recycled as much as possible. With a flywheel drive is not a speed control system, when the load comes, the motor speed drops to flywheel energy. However, the speed drop is very small, such as according to the speed range to describe D = 1.1 ~ 1.2 between, and the low speed running time is very short, after the load horse speed, therefore, with a flywheel motor and constant speed The system is not the same;
(4) The simplicity, cost, and reliability of metal resistors cannot be compared with other electrical components.
HC series slip speed-regulating force adding device adopts multi-level adjustment, usually adopts three-level adjustment, its characteristics:
(1) The utilization rate of the motor can reach 93.3%, which is equivalent to the motor capacity increase, which is 15% more than the motor with its own natural characteristics. That is, after the HC device is used for the 2800KW motor, the equivalent capacity has been increased to 3220KW. Therefore, the HC device It is very suitable for the place where the capacity of the motor is insufficient, and it creates excellent conditions for avoiding the replacement of large-capacity motors.
(2) The mechanical characteristics can be greatly increased, so that the rolling speed is high, the speed of the motor pick up after the load is high, and the storage capacity of the flywheel is large.
(3) Improve the power factor of the motor, save energy and reduce consumption.