DAiKIN KF-5-10 Proportional Amplifier Unlock the Full Potential of Your Hydraulic System with Proportional Valve Control

DAiKIN Proportional Amplifier KF-5-10: Precision Control for Hydraulic Proportional Valves

Introduction
In the demanding world of industrial automation and hydraulic control, achieving precise, stable, and efficient actuation of proportional valves is paramount. The DAIKIN KF-5-10 Proportional Amplifier (Minor Loop Control Driver for AC Power Supply) stands as a sophisticated solution engineered to optimize the performance of critical LEM-series proportional valves. Designed for integration with valves featuring minor feedback control (utilizing internal Linear Variable Differential Transformers - LVDTs), this amplifier delivers exceptional accuracy, resilience against environmental fluctuations, and reduced power dissipation. Its core mission is to translate low-power command signals into precisely controlled high-current outputs for proportional solenoids, enabling nuanced flow or pressure regulation within hydraulic systems found in applications like injection molding machines, metal forming presses, and sophisticated test stands.

Core Functionality & Technology
The KF-5-10 acts as the intelligent intermediary between a low-level control signal (typically 0-5V DC or a 1kΩ potentiometer) and the proportional solenoid of a LEM valve. Its defining characteristic is its Minor Feedback Control capability:

1. Spool Position Sensing: The amplifier connects to the valve's built-in LVDT (Linear Variable Differential Transformer) via Terminal 23. This sensor provides real-time, high-fidelity feedback on the actual spool position within the valve body.

2. Closed-Loop Correction: By continuously comparing the actual spool position (from the LVDT) to the commanded position (from the input signal), the amplifier generates a corrective error signal.

3. Precision Current Output: This error signal drives the amplifier's output stage, adjusting the current supplied to the proportional solenoid (Terminals 13/14) until the spool reaches the exact position demanded by the input command. This closed-loop approach virtually eliminates hysteresis and significantly improves valve resolution and repeatability.

Key Technological Advantages

1. Differential Transformer (LVDT) Integration: Direct detection of the spool position provides the fundamental basis for true closed-loop control, enabling the amplifier to compensate for friction, wear, and load variations within the valve itself.

2. Superior Constant Current Characteristics: The amplifier meticulously regulates the output current (0 to 850 mA for the KF-5-10) to the solenoid.

   • Voltage Fluctuation Immunity: Fluctuations in the AC mains supply (within the permissible -10% to +10% range) have negligible impact on the output current, ensuring stable valve performance even on unstable power grids.

   • Temperature Drift Compensation: Resistance changes in the solenoid coil due to temperature rise are automatically compensated for, maintaining consistent force output and valve positioning accuracy regardless of operating temperature.

3. Optimized Dither Control: Dither is a small, high-frequency AC signal superimposed on the main DC output current. It is crucial for overcoming static friction (stiction) in the valve spool, enhancing resolution, and minimizing hysteresis.

   • The KF-5-10 allows selection among three dither levels (High, Medium, Low) via simple jumper connections on Terminals 9, 10, 11, and 12. This enables fine-tuning for specific valve characteristics and application requirements (shipped with Terminals 9 & 11 shorted = Medium).

   • Precise control over dither frequency and amplitude ensures optimal valve response without causing excessive noise or wear.

4. PWM Current Control & Efficiency: Instead of traditional linear amplification, the KF-5-10 employs Pulse Width Modulation (PWM) to regulate the solenoid current. This method switches the output power transistors fully on or off rapidly.

   • Minimized Heat Generation: Power transistors dissipate significantly less heat when switching (compared to operating in a linear region), leading to a cooler-running, more reliable amplifier and reduced need for oversized heatsinks (evident in the compact design).

   • High Efficiency: PWM control inherently offers higher electrical efficiency, translating to lower operational costs and reduced thermal stress on components.

5. Robust Protection & Safety Features:

   • Overload Protection Circuit: Safeguards the amplifier and connected valve against damage from excessive current draw or short circuits.

   • Surge Voltage Absorption: Protects sensitive internal electronics from voltage spikes on the power lines.

   • Fuse Protection: A mains fuse (POWER SW terminal) provides primary overcurrent protection.

   • Earth Terminal (E): Essential for safety grounding.

Technical Specifications at a Glance

Installation, Wiring & Handling Considerations

• Terminal Functions: The terminal strip (24 points) is clearly defined. Critical connections include:

  • Power (1, 2, 3, 4, E): Mains AC Input (100/200/220V) and Earth.

  • Command Input (16, 17, 18): DC 0-5V (16+ / 17-) or Potentiometer (16, 17, 18). *Note: Terminals 16 & 17 are factory-shorted; do NOT remove this short for standard voltage input.*

  • Solenoid Output (13+, 14-): Connect to the DC 24V proportional solenoid coil. Use shielded cable.

  • LVDT Feedback (23+, 22-, 21 Shield): Connect to valve's position detector (LVDT). Use shielded cable, connect shield to Terminal 21.

  • Dither Selection (9, 10, 11, 12): Short 9-10 (Low), 9-11 (Mid), or 9-12 (High).

  • Ammeter (5+, 6-): For connecting a moving-coil DC ammeter (e.g., 1A). Crucially, terminals 5 and 6 MUST be SHORTED if no ammeter is connected.

  • +5V Supply (15+, 20-): Provides power for an external potentiometer.

  • Check (19): For zero point adjustment of LVDT (refer to detailed manuals).

• Ventilation: The enclosure features vent slots on left/right sides (5x4 slots each) and the bottom (12x3 slots). Ensure adequate airflow around the unit during installation within a control cabinet.

• Shielding: Mandatory. Always use shielded cables for the Command Input signal lines (DC INPUT / Pot) and the LVDT Feedback signal lines. Connect the cable shields to the designated amplifier shield terminals (Terminals 21 for LVDT, implied for Command via shielded cable connection to common ground/shield point) to minimize electrical noise pickup.

• Setting Adjustments: The unit features trimmer potentiometers for:

  • GAIN: Adjusts overall loop gain (affects response speed/stability).

  • ZERO: Fine-tunes the zero point offset.

  • MIN: Adjusts the minimum output current (command 0V).

  • MAX: Adjusts the maximum output current (command 5V). Calibration procedures should be followed as per the full operation manual.

Applications
The DAIKIN KF-5-10 amplifier is specifically designed for driving Daikin's LEM series direct-operated proportional control valves with minor feedback (LVDT). These valves are prevalent in industries requiring precise flow or pressure modulation:

• Plastics Machinery: Precise control of injection speed, pressure, and clamping force in injection molding machines.

• Metalworking: Accurate pressure and speed control in hydraulic presses, bending machines, and rolling mills.

• Test & Simulation Equipment: High-fidelity force, pressure, or motion control in material testers, fatigue test rigs, and flight simulators.

• Industrial Automation: Process control requiring proportional hydraulic actuation beyond simple on/off functionality.

Conclusion
The DAIKIN KF-5-10 Proportional Amplifier represents a mature and highly refined solution for closed-loop control of LVDT-equipped proportional valves. Its integration of minor feedback via the valve's internal LVDT sets it apart, enabling unparalleled accuracy and repeatability by directly controlling the critical variable – the spool position. Combined with its robust constant current output (immune to voltage and temperature variations), configurable dither optimization, efficient PWM drive, and comprehensive protection features, the KF-5-10 delivers reliable, high-performance control essential for demanding hydraulic applications. While requiring careful attention to wiring (especially shielding and terminal shorts), its design prioritizes stability and precision, making it a cornerstone component in systems where hydraulic control quality directly impacts process outcome and productivity.