Rexroth Bosch Group VT2000 Proportional Amplifier

VT2000 Proportional Amplifier Complete Guide: From Functional Principles to On site Troubleshooting

In industrial hydraulic systems, the control accuracy of proportional pressure valves directly depends on the performance of their electronic amplifiers. Bosch Rexroth's VT2000 series amplifiers are designed specifically for controlling direct acting and pilot operated proportional pressure control valves (without electrical position feedback). With the continuous operation of old equipment, many factories are still using VT2000 5X series or earlier 4X series amplifiers. When the amplifier malfunctions or needs to be replaced, engineers often face difficulties such as spare parts shutdown and missing documents. This article is based on the technical manual of VT2000, comprehensively analyzing its functional block diagram, terminal definitions, technical parameters, jumper settings, and on-site troubleshooting steps, helping hydraulic maintenance and system integration personnel quickly grasp the key points of using and replacing the amplifier.

Product positioning and core features of VT2000

VT2000 is a single channel proportional amplifier that adopts the European standard Euro card (100 × 160mm) size and is connected to the system through a 32 pin DIN 41612 male connector. The main design objective is to provide an adjustable current drive signal with ramp function for proportional pressure control valves. This amplifier is suitable for proportional pressure valves without electrical position feedback (i.e. open-loop control), which can change the spool position or pilot pressure by adjusting the electromagnetic current.

The core features include:

Differential input: can accept 0~+10V signals from PLC or other controllers, isolated from internal reference potential.

Additional command value input: 0~+9V (based on measuring zero position MO as a reference).

Slope generator: The time for ascending and descending slopes can be adjusted separately, and rapid slope can be forced through external contacts.

Clock type current output stage: outputs PWM modulated current with adjustable flutter frequency (100Hz or 200Hz) to reduce valve core friction.

Protection functions: reverse polarity protection of power supply, short circuit protection of electromagnetic cable, over temperature shutdown (no separate alarm signal).

Measurement socket: The front panel provides "w" (instruction value) and "I" (actual current value) test points for easy debugging.

This amplifier needs to be used in conjunction with an external power supply and card slot. Rexroth recommends using the VT3002-2X/32 single card slot (excluding power supply) and the VT-NE30-1X compact power supply (115/230VAC to 24VDC, 70VA).

Order code and version compatibility

The ordering code for VT2000 follows Rexroth's coding system. Although the complete code table is not listed in the document, important information is pointed out that the 5X series amplifier can be interchangeable with the 4X series under factory settings, provided that the ramp time is set to 5 seconds and the clock frequency is set to 200Hz. If you want to replace the 4X with 5X, you need to order an additional blind plate with a width of 4TE (due to differences in front panel width). Users should pay attention to checking the settings of the original system to ensure that the new amplifier jumper configuration is consistent with the old machine.

Detailed explanation of functional block diagram and signal flow

In order to effectively troubleshoot, it is necessary to understand the signal processing link inside VT2000. Below, we will explain one by one according to the signal flow direction.

3.1 Instruction value input level

The amplifier provides two input channels for instruction values:

Command value input 1: Voltage range 0~+9V, reference potential is MO (measure zero position). This input can be obtained by dividing it with an external potentiometer using an internal+9V regulated power supply. If the user uses an external potentiometer, the "Gw" potentiometer on the front panel of the amplifier must be adjusted to the maximum or to the position corresponding to the required maximum pressure.

Instruction value input 2 (differential input): voltage range 0~+10V, input resistance 100k Ω. Differential input is suitable for external electronic devices (such as PLC) and amplifiers that are not grounded together. When using differential input, two signal lines (28c and 30ac) must be connected or disconnected simultaneously.

The two command values are summed internally ([2]) and then sent to the command value attenuator (potentiometer "Gw" [3]) to limit the maximum output current (i.e. maximum pressure). The attenuated signal enters the ramp generator [4].

3.2 Slope Generator

The ramp generator converts step command values into ramp signals. The ramp time (from 0% to 100% command value) can be adjusted by two potentiometers to adjust the rise time and fall time respectively. The slope time range depends on the setting of jumper S1:

S1 jumper at "1s" position: ramp time 30ms~1s

S1 jumper at "5s" position: ramp time 30ms~5s