NAA 70/2-D by Bosch Rexroth Indramat

The NAA 70/2-D is a mains connection module produced by Bosch Rexroth Indramat for the VM Amplifier Drives series. As a dedicated interface between the plant's supply network and the drive stack, the unit distributes incoming power and houses protective components. It also coordinates charging of the DC link in multi-axis systems, helping the connected drives start in a controlled manner and reducing electrical stress on upstream supply components.

It is designed for a three-phase supply, and the incoming line voltage is 400 VAC, matching standard industrial low-voltage grids and allowing the unit to be fed from common service transformers. Under sinusoidal conditions, the module can route up to 47 kVA of apparent power at a line frequency of 50 Hz, providing capacity for several VM inverters mounted in the same rack. The internal busbars and terminations accommodate the three-phase conductor set without additional distribution hardware. Thermal energy is removed by natural convection, so cabinet layouts must allow unobstructed upward airflow instead of relying on forced fans. An integrated charging circuit gradually precharges the intermediate DC capacitor to limit inrush spikes during startup.

Overcurrent and line-disturbance protection are provided by a 100 A (660 V) semiconductor fuse in the high-speed (M1-f1) category, allowing fast clearing times that protect both the rectifier bridge and downstream drives. A housing mass of 8.4 kg supports a built-in power contactor that disconnects the supply when a fault is detected, and the integrated charging connection keeps wiring compact. The built-in integrated additional filter attenuates conducted harmonics, which can reduce interference on the supply line. Mounting points, bus connectors, and phase orientation are arranged to match adjacent amplifier modules in the same rack.