VT-SR7-1X/0/A4VS.250HS

The VT-SR7-1X/0/A4VS.250HS is an electrohydraulic control card from Bosch Rexroth Indramat supplied within the VT-SWMA Modules series. Designed for rack installation, the board conditions analog command and feedback signals and delivers modulated current to proportional directional or pressure valves in industrial automation. By converting low-level control voltages into precise spool-drive currents, the module allows programmable logic controllers to regulate hydraulic actuators with closed-loop accuracy.

Signal processing uses an actual-position input range of ±10 V, matched by a command input range of ±10 V so the card can compare demanded and measured positions directly. The input stage has an impedance of 50 kΩ, minimizing the electrical load on external transducers. Internal circuits operate from ±24 VDC, while a separate ±15 V auxiliary rail stabilizes the reference amplifiers. The output stage supplies up to ±60 mA of valve current and superimposes a 3 mA dither signal at 340 Hz to help overcome spool stiction. This output supports precise control of compatible A4VS proportional valves across the available command range. A relay energized by a +24 V activation signal isolates the power path when the controller is disabled. Its coil has a resistance of 700 Ω, which limits current through the relay circuit.

The board has an area of 100 × 160 mm, following the Eurocard format used for industrial control racks. Its aluminum front panel measures 128.4 mm in height, allowing the card to fit into 3 U subracks with appropriate ventilation and clearance. Connection to the backplane is made through a 32-pin DIN 41612 Form D header that carries power, input and output signals, and the relay’s nominal 26 V supply. The header provides a single organized interface between the control card and the surrounding rack circuitry. The relay closes within 4 ms, allowing the hydraulic control path to respond quickly to an enable command. The rack format also keeps the analog signal paths and power connections contained within the card assembly.