The main induction furnace circuit diagram of the series inverter one-drive-two furnace (hereinafter referred to as the series circuit) is that one power supply can feed two electric furnaces for smelting at the same time, or one furnace for smelting, and the other one for heat preservation. Take the electric induction furnace with a one-driven two-circuit series circuit as an example, the inverter part is composed of two half-bridge inverter circuits in series. During the use of this series circuit, the rectifier circuit is always in the full conduction state, so the power factor is not less than 0.95 (the rectifier output voltage Ud is constant). The power output of the series circuit is controlled by adjusting the size of the inverter conduction angle. The power factor referred to here is C0S&=P ／ S, where: P active power. S Apparent power.
Active power reflects the magnitude of work done by AC on resistive load or the efficiency of converting it into other forms of energy (such as thermal energy, mechanical energy, and light energy). Take the one-drive-two series circuit as an example, inverter bridge 1 (10 t furnace body) and inverter bridge 2 (30 t furnace body) each give a given output voltage of 10 V, and the two given output voltages are usually controlled by a multiplier integrated block.
1) When the output voltage of inverter bridge l is 1 V, the output power of inverter bridge l is 10% of the rated power, and the maximum output voltage of inverter bridge 2 can reach 9 V. The output power of inverter bridge 2 is 90% of the rated power.
2) When the output voltage of inverter bridge 1 is 10 V, the output power of inverter bridge 1 is 100% of the rated power, and the output power of inverter bridge 2 is 0.
3) When the output voltage of inverter bridge l is 6 V, the output power of inverter bridge l is 60% of the rated power. At this time, the maximum output voltage of inverter bridge 2 can reach 4 V, and the output power of inverter bridge 2 is 40% of the rated power; By analogy, the power of inverter bridge 1 (10 t furnace body) and inverter bridge 2 (30 t furnace body) are arbitrarily distributed.
4) When the output voltage of inverter bridge 1 is 3 V, the output power of inverter bridge 1 is 30% of the rated power.
The inverter part of the main induction furnace circuit diagram of the parallel circuit medium frequency electric furnace is a parallel circuit. During the use of this parallel circuit, the power output is controlled by adjusting the size of the rectifier conduction angle, and the rectifier circuit has been in a regulated state (the rectifier output voltage is now constantly changing). The power factor of the parallel circuit is directly proportional to the commutation angle.
When using a large and small medium-frequency power supply (parallel circuit) plus change-over switch switching mode, there are problems such as an excessive working current of change-over switch, skin effect of working current of change-over switch (working frequency 50 nz) and switching complexity, which makes it difficult to work stably. Generally, the working current of the furnace change switch=medium frequency current × Q (quality factor coefficient is 12).
Characteristics of Series Inverter One-Drive-Two Induction Furnace Circuit Diagram
1) Application of new reactive power compensation-electric transformer technology. When the load is in series resonance, the rectifier bridge in the variable frequency power supply works in the fully conducting state, and the system power factor COS I>0.95.
2) The organic combination of power control and multiple power supply distribution technology. (One transformer) A set of rectifier systems can distribute electric energy steplessly to multiple inverters within the rated range, and the inverters can adjust power steplessly to supply power to the induction furnace according to the process requirements.
3) The system has a high degree of automation and complete optimization and combination functions.
4) Significant energy-saving effect:
① The average COS of frequency conversion electric furnace with parallel inverter technology ≥ 0.85; With series inverter technology, a COS towel ≥ 0.95 can save 10% energy.
② Compared with other circuits, the current of the load circuit is 10-12 times smaller. It can save 3% of operation power consumption.
③ There is no need for a large-capacity filter reactor, and power consumption can be saved by 1%.
④ Each induction smelting furnace is powered by a group of inverters independently, which can save 1% of power consumption without installing a large current furnace change switch.
⑤ In the operating power characteristic curve of the series inverter, there is no power concave part, that is, the power loss part, which significantly shortens the melting time, increases the output and saves power consumption, and can save 7% energy.
⑥ The above five items save 22% of energy (electricity).