1, pure resistive load (cold and hot resistance change small load)
The way of adjustment model is:
A, cycle (duty ratio control) or frequency zero power technology and high power SSR, overcome the way of regulating the shortcomings of low power factor, power grid pollution.
B, the common way of regulating
C, the zero SSR mode frequency of zero load current in the sine wave is uniformly distributed for the unit, many sets of equipment operation, total power current relative balance (avoid cycle control mode current concentration), and improve the uniformity of furnace temperature, avoid ammeter firing pin, it is important that improves the utilization rate of power supply and to avoid power equipment of capacity, node effect is very obvious
2, silicon carbon rod (700 ℃ negative features, namely the resistance to negative temperature characteristic, after 700 ℃ for positive temperature characteristics)
Can be adjusted using phase shifting. Slow start > 10 s, maximum current limitations, output limit, can surge tank first, after work.
Unfavorable adopts the zero passage method full voltage start, otherwise it will cause too much impact current, easy to damage the silicon controlled rectifier and accelerate the aging of silicon carbide. Generally adopt soft start is greater than 1 minute, to avoid the negative resistance near the 700 ℃ impact current (new). Can adopt step-down transformer, silicon carbon rod series or the centre ground can be adjusted separately for each road power and balance of silicon carbide aging control panel.
3, pure metals (carbon molybdenum rods, molybdenum wire, such as platinum R - T) for linear positive temperature features:
Can adopt step-down transformer phase shift regulating mode. Add soft start > 10 s, maximum current limit, the output limiter, linear limiter.
Although such load change of heat and cold resistance, resistance has a linear relation with temperature, through the transformer step-down, current limit and cooperate with multiple sets of PID and power limit of the instrument, can design the low, medium and high current limit.
4, transformer control:
On the inductance load, using electric soft start gradually paramagnetic gentle turn off gradually in the reduction of magnetic field; Variable dc pulse width trigger technology, can provide enough reach the thyristor with locking in current time, avoid the narrow pulse trigger pulse transformer is not reliable.