Industrial electric furnace temperature control method
Automatic furnace temperature control --- refers to automatically turning on or off the heat source energy supplied to the furnace according to the deviation of the furnace temperature from a given temperature, or continuously changing the amount of heat source energy to stabilize the furnace temperature within a given temperature range. Meet the needs of heat treatment process.
The commonly used adjustment rules for automatic control of heat treatment temperature include two-position, three-position, proportional, proportional integral, and proportional integral differential.
1) Two-position adjustment-it only has two states of on and off. When the furnace temperature is lower than the set value, the actuator is fully open; when the furnace temperature is higher than the set value, the actuator is fully closed. (Actuators are generally selected as contactors)
2) Three-position adjustment-it has two given values of upper and lower limits. When the furnace temperature is lower than the given value of the lower limit, the entertainer is fully open; when the oven temperature is between the given value of the upper and lower limits, the actuator is partially opened ; When the furnace temperature exceeds the upper limit given value, the actuator is fully closed. (If the tubular heater is a heating element, the three-position adjustment can be used to achieve different heating and insulation power)
3) Proportional adjustment (P adjustment)-The output signal (M) of the regulator is proportional to the deviation input (e). which is:
M = ke
In the formula: K ----- proportional coefficient
There is a corresponding proportional relationship between the input and output of the proportional regulator at any time. Therefore, when the furnace temperature change is balanced by the proportional adjustment, the deviation of the furnace temperature cannot be increased to a given value-called "static difference" "
4) Proportional integral (PI) adjustment-In order to "static difference", add integral (I) adjustment integral to proportional adjustment. Adjustment means that the output signal of the regulator and the deviation increase with time, until the deviation is eliminated. There is no output signal, so the combination of "static difference" proportional adjustment and integral adjustment is called proportional integral adjustment.
5) Proportional-integral-derivative (PID) adjustment-Proportional-integral adjustment will increase the adjustment process and increase the amplitude of temperature fluctuations. To this end, derivative (D) adjustment is introduced. Differential adjustment refers to the differential ratio of the regulator's output and deviation to time. The differential regulator has an adjustment signal output when the temperature changes "emerging". The faster the change rate, the stronger the output signal, so it can speed up the adjustment speed. To reduce the temperature fluctuation range, the combination of proportional adjustment, integral adjustment and differential adjustment is called proportional integral differential adjustment. (Generally adopt thyristor regulator as actuator)