VT-KRRA2-537-20 Rexroth Valve Amplifier 3.7A 2-Axis

Product Overview

The VT-KRRA2-537-20/V0/ (Material No. 0811405082) is a dual-channel analog valve amplifier card from Bosch Rexroth’s VT-KRRA2 series, designed specifically for controlling directly operated high-response servo solenoid valves of the 4WRPH 10…L-2X series. Built on component series 2X, it is a double Euro-card (233.4 × 160 × 30 mm) capable of simultaneously operating two NG6/NG10 high-response valves.

The core function of the VT-KRRA2-537-20/V0/ is to convert analog command signals (0…±10 V differential input) from an external electronic control system (PLC or motion controller) through internal signal conditioning into solenoid drive current (maximum 3.7 A), enabling continuous and precise control of hydraulic actuator velocity, force, or position.

In the model code, “537” indicates the card is designed for valves with a maximum solenoid current of 3.7 A, “20” denotes component series 2X, and “V0” is the version identifier. The card supports 2-channel operation, making it particularly suited to applications requiring multi-valve coordinated control, such as 2-axis synchronous control in presses and profile machining in machine tools.

As a drop-in replacement, the amplifier card is fully compatible with the OEM Rexroth specification in installation dimensions, electrical interface (DIN 41612 32-pin connector), and performance characteristics. Every unit undergoes 100% simulation-based testing prior to shipment, covering output current accuracy, step response time, null stability, and short-circuit protection verification.

Technical Specifications

All parameters below are based on Bosch Rexroth official datasheet RE 30049/11.02 and verified supplier technical pages:

• Complete Model: VT-KRRA2-537-20/V0/

• Material Number (MNR): 0811405082

• Brand: Bosch Rexroth

• Product Series: VT-KRRA2 series, component series 2X

• Product Type: Analog valve amplifier card, double Euro-card format

• PCB Dimensions: 233.4 × 160 × 30 mm (European double format)

• Suitable Valve Types: 4WRPH 10…L-2X series directly operated high-response valves

• Number of Channels: Dual-channel (2 channels, for simultaneous operation of 2 high-response valves)

• Supply Voltage: 24 V DC nominal (permissible range 21 – 40 V; also supports 21 – 28 V single-phase full-wave rectified AC)

• Supply Ripple: < 10% (VT 11110 capacitor module recommended when ripple exceeds 10%)

• Power Consumption: 55 VA

• Current Consumption: Max. 2.7 A

• Command Value Input: 0…±10 V differential input, input resistance ≥ 100 kΩ

• Digital Input (Enable): Active voltage 8.5…40 V, input resistance RE = 100 kΩ

• Solenoid Output Current: Max. 3.7 A per channel, short-circuit protected

• Position Transducer Supply: ±15 V, max. 200 mA, short-circuit protected

• Reference Voltage Output: ±10 V (Imax = 10 mA)

• Digital Output (Cable Break Alarm): No error 24 V; error 0 V (Imax = 100 mA)

• Electrical Interface (Signals): 2 × DIN 41612, 32-pin, type D

• Electrical Interface (Valve & Supply): Screw-type plug connectors on front (ST 4, 5 and ST 9, 10)

• LED Indicators: Green — enable; Yellow — cable break actual value; Red — undervoltage

• Ambient Temperature Range: 0 °C to +70 °C

• Storage Temperature Range: -20 °C to +70 °C

• Weight: 0.54 kg

• Compatible Card Holder: Double connector block 1834486002

Note: Specifications are based on Bosch Rexroth official datasheet RE 30049/11.02 and verified supplier technical pages. This card is suitable for 4WRPH 10…L-2X series high-response valves. The series also includes VT-KRRA2-527-20/V0/2CH (Material No. 0811405083), suitable for 4WRPH 6…L-2X series valves. Always verify against the complete model code during selection.

Key Technical Advantages

1. Dual-Channel Double Card Design for High-Precision Two-Axis Synchronous Control

The VT-KRRA2-537-20/V0/ employs a double Euro-card architecture, enabling a single card to simultaneously control two high-response servo solenoid valves. This integrated design eliminates the need for two separate single-channel amplifier cards in applications such as press two-axis synchronous control and profile machine tool two-axis coordinated motion, significantly improving control cabinet space utilization and reducing system wiring. Both channels share an internal DC/DC converter supply, providing ±15 V stable power to command value encoders and position transducers.

2. Closed-Loop Controlled Output Stage with Short-Circuit Protection

The amplifier card’s output stage employs a closed-loop control architecture that continuously monitors and dynamically corrects solenoid current, ensuring precise matching between output current and command signal. The output stage features short-circuit protection, automatically cutting output in the event of solenoid cable short circuits to protect both the amplifier card and the proportional valve from damage. This protection mechanism is critical for long-term reliable operation of high-response valves, effectively reducing equipment damage risk from field wiring faults.

3. Enable Input and Cable Break Detection

The amplifier card is equipped with a digital enable input (active voltage 8.5…40 V), allowing the system controller to remotely enable or disable amplifier output via logic signal. An actual value cable break detection function is also integrated: when the position transducer feedback signal cable is disconnected, a yellow LED illuminates to provide clear fault indication to operating personnel. A green LED indicates enable status, and a red LED indicates supply undervoltage (below 18 V). This triple-LED diagnostic system enables highly efficient on-site troubleshooting.

4. Wide Voltage Input Range for Industrial Supply Adaptability

The supply voltage is 24 V DC nominal with a permissible range of 21 – 40 V, and the card also supports 21 – 28 V single-phase full-wave rectified AC voltage. This wide voltage design enables the amplifier card to adapt to various industrial field supply conditions, including battery-powered and rectified power supply scenarios. When supply ripple exceeds 10%, the VT 11110 capacitor module can be used to stabilize voltage, ensuring the amplifier maintains stable output performance in high-ripple environments. The power supply includes reverse polarity protection, reducing the risk of equipment damage from field wiring errors.

5. Precision Manufacturing and 100% Simulation-Based Testing

The amplifier card uses German-made original components and strictly follows Rexroth industrial manufacturing standards. IC socket test points on the front side enable maintenance personnel to quickly measure signal parameters during commissioning or servicing without disassembling the card. Every unit undergoes 100% simulation-based testing prior to shipment, covering output current accuracy, step response time, null stability, and short-circuit protection function verification, ensuring delivered performance matches the official datasheet.

Application Areas

• Press Two-Axis Synchronous Control: Simultaneously driving two high-response valves for precise synchronization of hydraulic cylinders on both sides of the slide, suitable for hydraulic and mechanical presses

• Profile Machine Tools & Forming Equipment: Two-axis coordinated control for precision profile machining of complex contours

• Machine Tool Feed Axis Control: Flow and direction control for precision hydraulic feed axes in CNC machine tools

• Injection Molding Machines: Flow and pressure closed-loop control during injection and hold-pressure phases

• Industrial Automation Lines: Integration with PLC for digital control of high-response valves

• Material Testing Systems: Dual-channel independent control for electro-hydraulic servo loading systems

• Vibration Tables & Test Rigs: Dual-axis precision flow control under high-frequency dynamic response conditions

Expert Maintenance Tips

Pre-Installation Checks:

• Verify card holder slots are clean and free of dust; inspect DIN 41612 connector pins for bending or oxidation

• Confirm supply voltage is within 21 – 40 V range; a regulated power supply is recommended with ripple controlled below 10%

• Check solenoid cable specifications: use Ø 1.5 mm² cable for runs up to 20 m, Ø 2.5 mm² cable for 20 – 60 m

• Use shielded 4-wire cable (0.5 mm² cross-section) for position transducer connections

Commissioning and Adjustment:

• Zero calibration: Adjust valve zero via the on-board zero potentiometer to ensure the valve is at center position with zero input signal

• Enable signal: Verify enable input (8.5 – 40 V) reaches the card correctly; green LED lit indicates output is active

• Reference voltage check: Confirm ±10 V reference voltage output is stable (Imax = 10 mA) for command value encoder supply

• Position transducer supply: Verify ±15 V transducer supply is normal (Imax = 200 mA) with load resistance ≥ 10 kΩ

• Ripple handling: If supply ripple exceeds 10%, connect a VT 11110 capacitor module at the supply input

Troubleshooting Guide:

• No output from card: Check 24 V DC supply (verify red LED is not lit), verify enable signal reaches the card (confirm green LED is lit), measure fuse continuity

• Valve actuates but speed is unstable: Check command signal for interference, verify solenoid cable specifications and length meet requirements, inspect hydraulic fluid cleanliness and spool condition

• Yellow LED cable break alarm lit: Check position transducer feedback cable for disconnection, verify sensor cable connection integrity

• Low output current: Check load impedance is within matching range; verify solenoid coil has no short or open circuit; measure current consumption per valve (normal ≤ 2.7 A, extreme conditions up to 3.5 A)

• Red LED undervoltage indication: Check whether supply voltage drops below 18 V; verify excessive voltage drop in supply lines