Product Description:

The RD51.2-4B-007-L-A2-FW is a drive controller produced by Bosch Rexroth Indramat as part of the RD 500 Drive Controllers series. In an automation cell, it converts fixed-frequency supply power into a variable output for standard induction motors, letting a PLC vary speed and torque without mechanical gear changes. By integrating control electronics, power semiconductors, and protective features, the unit serves as the interface between the plant’s three-phase mains and the connected motor. It is suited to cabinet-mounted duties such as conveyors, pumps, and other variable-speed machinery that uses induction motor control. The controller is intended for applications that need adjustable motor speed from a standard three-phase supply while keeping the drive package in one enclosure.

It is rated for 7.5 kW, providing continuous shaft power when supplied within the 380 to 480 V window. The internal rectifier section accepts a three-phase AC converter feed and remains stable with line variation of ±10 %. Motor excitation follows a U/f curve control algorithm, so voltage rises proportionally with frequency to keep magnetic flux constant and avoid core saturation. This control method works well with general-purpose squirrel-cage motors and supports open-loop speed control without motor feedback devices.

For dynamic stopping, the controller incorporates a built-in brake chopper that diverts regenerative energy into an external resistor bank. Thermal losses from the power section are removed through forced air cooling, which directs cabinet airflow across the heat sink. The drive uses an integrated mains filter to reduce conducted emissions on the supply lines. The safety block includes a starting lock-out and an external standby-power input so the drive can be isolated without shutting down the entire cabinet. This arrangement is useful where repeated deceleration or controlled stopping is required during normal machine operation.