Rexroth Bosch Group VT2000 Proportional Amplifier

If the step amplitude of the instruction value is less than 100% (such as when the attenuator has been limited or the input is only 5V), the actual ramp time will be proportionally shortened. In addition, the up or down ramp can be forcibly shortened to the minimum value (about 30ms) through the external contact "ramp up/down" for emergency rapid response.

The output signal of the ramp generator is the internal current command value, which can be monitored at the measuring socket "w". The 100% instruction value corresponds to a+6V voltage (note that it is not 10V, which is easy to misunderstand).

3.3 Bias current superposition and current regulator

After the ramp signal is sent to the current regulator [5], it will be added to the bias current ("Zw" potentiometer R130). The bias current can be adjusted within the range of 0~300mA, used to overcome the dead zone of the valve or set the minimum pressure. Adjusting R130 can change the zero offset.

3.4 Clock output stage and jitter

The output of the current regulator is modulated by PWM (clock frequency of 100Hz or 200Hz, selected by jumper S2) and then sent to the output terminal of the electromagnet. This clock like current generates a superimposed flutter signal (dither) in the electromagnet, which helps to reduce the static friction and hysteresis of the valve core. The maximum current of the output stage is 800mA (+10%/-5%), and the corresponding load resistance is 19.5 Ω (the cold resistance of the electromagnet is about 20-30 Ω). The output stage has short-circuit protection and will automatically shut down when overheated - but will not emit a fault signal, which needs to be noted when troubleshooting "sudden valve failure".

The actual electromagnetic current can be monitored at the measuring socket "I", with 800mA corresponding to 800mV (i.e. 1mA/mV). This is a very intuitive proportional relationship.

3.5 Internal power supply

The amplifier is powered by 24VDC (allowing+40%/-5%, i.e. 22-35V). Internally generated ± 9V regulated power supply, with+9V used for external potentiometer power supply and -9V used as a reference for measuring zero position MO. Attention: MO has been raised by+9V relative to the 0V power supply and is not isolated. Therefore, it is absolutely forbidden to connect MO to a 0V power supply, otherwise it will short-circuit the internal power supply. Only high internal resistance instruments (Ri>100k Ω) can be used for measurement.

Terminal allocation and wiring guide

VT2000 adopts a 32 pin male connector (DIN 41612, D-type). Although the document does not provide a complete list of terminals, key terminals can be inferred from the troubleshooting steps and diagrams:

Terminal signal description

24ac+24V power supply working voltage positive pole

18ac 0V power supply working voltage negative pole

10ac+9V output for external potentiometer use

12ac instruction value 1 input 0~+9V (relative to MO)

28c differential input+0~+10V

30ac differential input - reference potential

22ac electromagnet+connected to one end of the proportional valve coil

20ac electromagnet - other end of the wiring coil

6,8 Ground/Shielded Connection to System Grounding

16ac, 14mc slope external contacts are used for fast slopes (please refer to the complete manual for details)

Key points of wiring:

Electromagnetic connection wires must not use plugs with freewheeling diodes or LED indicator lights, otherwise it will interfere with PWM output or generate reverse voltage and damage the amplifier.

The instruction value cable must be shielded, with the shielding layer grounded on the amplifier side and the other end suspended.

Electromagnetic cables should also be shielded (recommended). When the length is ≤ 50m, use LiYCY 1.5mm ² cable. If it is longer, consult the manufacturer.

Keep a distance from strong electrical cables (power lines) and at least 1 meter away from antennas, radio stations, and radar equipment.

Jumper setting and potentiometer function

There are multiple jumpers on the VT2000 board (located on the PCB and labeled with nameplates) used to configure the basic working mode. Users should record the actual settings and keep them the same when replacing.

5.1 S1- Selection of Slope Time Range

Position "1s": The maximum slope time is about 1 second

Position "5s": Maximum ramp time of approximately 5 seconds

The factory setting is usually 5 seconds to ensure compatibility with the 4X series.

5.2 S2- Clock Frequency Selection

100Hz

200Hz

The factory is set to 200Hz. Different valves may have requirements for vibration frequency, and too high or too low can cause valve core vibration or increased hysteresis.

5.3 Other jumpers (such as instruction value source selection)

The document mentions that if using an internal command value potentiometer (i.e. an external potentiometer connected between 10ac and 12ac), a jumper must be inserted between 10ac and 12ac. This jumper is used to lead the internal+9V to the command value input. The specific location needs to refer to the markings on the PCB (the circles in the figure represent user settings, and the solid circles represent factory settings).