1. Working Principle of Series One-Drive-One Intermediate Frequency Furnace
The core structure of the series one-drive-one intermediate frequency furnace: three-phase rectifier unit → DC smoothing reactor → inverter unit → series resonant circuit (induction coil + compensation capacitor) → smelting load.
Core characteristics of series resonance:
The furnace coil inductance and compensation capacitor form a series resonant circuit. Under resonance state, the equipment achieves the highest output efficiency and stable power output.
Under no-load empty furnace condition, only voltage is established, and the active power cannot be increased, which is a normal working condition.
After loading materials for smelting, the resonant point is adjusted by matching capacitors to realize normal full-power output.
2. Pre-Commissioning Comprehensive Inspection
2.1 Water Circuit and Mechanical Inspection
The furnace body, induction coil and water-cooled cable are firmly installed and fixed without deformation or looseness. The cooling water circuit is unobstructed without leakage or blockage, the water circulation system works normally, and all connecting parts are well sealed.
2.2 Electrical Insulation Inspection
Check the insulation resistance of the induction coil, compensation capacitor and inverter power device to the ground. The insulation performance must reach the standard without breakdown, electric leakage or aging damage. The overall equipment grounding is reliable with firm connection of the grounding loop.
2.3 Power Wiring and Power Supply Inspection
The phase sequence of three-phase incoming power supply is correct without phase loss or virtual wiring. The main circuit wiring of rectifier, inverter, capacitor and furnace coil is correct without wrong connection or short-circuit hidden danger. The control circuit, trigger circuit and signal feedback circuit are well connected without broken wire or poor contact.
3. Step 1: No-Load Commissioning (No Furnace Material)
3.1 Independent Test of Rectifier Unit
Disconnect the inverter output loop, start the rectifier part independently, adjust the voltage output stably, and observe the working state of the rectifier. It is normal if the equipment runs without abnormal noise, abnormal heating or tripping protection.
3.2 Inverter No-Load Oscillation Test
Connect the induction coil and compensation capacitor, leave the furnace without any furnace material in pure no-load state, start the intermediate frequency power supply, and slowly increase the power setting.
Normal performance: The equipment starts oscillation smoothly, the intermediate frequency voltage is stably established, the DC current remains at a low value, the active power cannot be raised, and there is no ignition, abnormal noise or vibration during operation.
Abnormal performance: If the no-load current is too large, the power increases abnormally, fails to oscillate or trips frequently, stop the machine immediately to troubleshoot the capacitor, inverter device and coil insulation fault.
4. Step 2: On-Load Resonance Matching (Core of Commissioning)
4.1 Furnace Material Filling Requirements
Fill the furnace with an appropriate amount of clean furnace material with moderate block size, evenly fill the effective working area of the induction coil to ensure good electromagnetic coupling. It is forbidden to put wet materials or impurity waste materials into the furnace.
4.2 Resonance Capacitance Matching Adjustment
Put all compensation capacitors into operation first, slowly increase the power setting, observe the operating state of equipment voltage, current and power, and finely adjust the number of put-in capacitor groups step by step:
If the voltage is on the high side, the current is low and the power is difficult to increase, properly reduce the put-in capacitors.
If the voltage is low, the current surges and over-current tripping is easy to occur, properly add more capacitors.
Fine tune repeatedly until the operating sound is stable, the voltage and current ratio are balanced, and the power output reaches the optimal state. Lock the current capacitor configuration as the best resonant working point.
5. Step 3: Power Setting and Protection Parameter Configuration
5.1 Gradual Power Increase
After resonance matching is completed, it is forbidden to directly set full power. Adopt the step-by-step power increase method. Stabilize and observe for a period after each adjustment, monitor the overall operating state of the equipment, and continue to increase power only if there is no abnormal temperature rise, jitter or alarm.
5.2 Protection Function Setting
Set the threshold values of over-current, over-voltage, water temperature and water pressure reasonably according to the factory standard and actual working conditions of the equipment. Ensure the protection loop acts reliably in case of overload, over-temperature, water shortage and under-voltage, so as to avoid damage to power devices and furnace body equipment.
5.3 Fine Adjustment of Inverter Trigger Angle
Fine tune the inverter trigger advance angle according to actual working conditions to ensure stable inverter operation state, no frequency drift and no waveform distortion, adapting to long-term smelting operation.
6. Step 4: Full-Load Trial Operation and Acceptance
Fill with rated smelting materials, steadily rise to full-power working condition, and conduct long-term continuous trial operation. Observe the power supply voltage, loop current, equipment temperature rise, water circuit circulation and operating noise throughout the whole process, and record the overall operation performance.
Acceptance standard: Stable power output, no unreasonable tripping, no ignition and peculiar smell, normal temperature rise of devices, qualified smelting efficiency, and sensitive and reliable response of all protection functions.
7. Common Faults and Solutions in Series One-Drive-One Commissioning
7.1 Power Cannot Be Increased All the Time
It is mainly caused by improper matching of resonant capacitors, insufficient furnace material filling, excessively thick furnace lining and abnormal turn-to-turn insulation of induction coil. Solve the problem by re-matching resonant capacitors, standardizing furnace material filling and checking coil insulation.
7.2 Abnormally High No-Load Current and Power
It is mostly caused by leakage of damaged compensation capacitors, soft breakdown of inverter power devices and turn-to-turn short circuit of induction coil. Detect and replace faulty devices one by one, and recheck insulation with megohmmeter.
7.3 Frequent Over-Current Tripping During Operation
The causes include insufficient configuration of resonant capacitors, wet furnace materials, poor water circuit heat dissipation and excessively low protection threshold. Add matching capacitors, dry furnace materials, overhaul water circulation and reasonably adjust protection parameters.
7.4 Equipment Fails to Start Oscillation Normally
Check and troubleshoot the trigger pulse loop, conduction state of inverter devices, capacitor put-in wiring and open-circuit fault of induction coil, repair lines and damaged components to restore normal operation.
8. Commissioning Summary
The core commissioning points of series one-drive-one intermediate frequency furnace are completing basic pre-inspection, verifying machine under no-load, matching resonance with loaded materials, increasing power step by step and setting protection parameters.
Operate in strict accordance with the standard process, avoid long-time high-power no-load operation and one-time full-load commissioning. It can not only complete equipment commissioning quickly, but also effectively protect core components such as thyristors, capacitors and induction coils, and ensure long-term stable smelting operation of the equipment.