175H1203 by Danfoss

The 175H1203 is an AC variable-frequency drive built by Danfoss and supplied within the VLT 3000 Variable Speed Drives series. The unit converts fixed-frequency three-phase mains power to a regulated pulse-width-modulated output so that induction motors can accelerate, decelerate, or hold speed in automated conveyors, pump stations, and fan arrays. By providing closed-loop speed control and programmable start limits, the drive helps reduce mechanical shock, improve energy efficiency, and maintain steady process throughput.

Under constant-torque duty, the drive delivers an apparent power of 9.3 kVA and draws a maximum input of 13.0 A while supplying 13.0 A to the motor terminals. When switched to the variable-torque profile, capacity rises to 11.5 kVA, permitted by a higher peak line demand of 17.0 A; in this mode, the controller can pass 16.0 A to centrifugal loads such as fans. The constant-torque mechanical output is rated at 5.5 kW, giving a reference point for matching the inverter with suitable motors. All operating ranges are synchronized to a mains frequency of 50/60 Hz. Because each enable cycle energizes DC-link capacitors, the product is limited to two switch-ons per minute, a restriction that helps prevent wear on the power stage.

Field wiring is simplified by a maximum conductor size of 2.5 mm², which accommodates common control-cabinet terminal blocks without requiring larger cable paths. Upstream protection uses a pre-fuse value of 25 A, so the semiconductor bridge can be isolated quickly during fault conditions. On variable-torque applications, the inverter can sustain an output line current of 16.0 A, translating to a shaft power capability of 7.5 kW for high-airflow fans and pumps. The two-starts-per-minute limit should be observed so input rectifier stress remains within the intended operating range.