6SE6420-2UD21-1AA1 Variable Frequency Drive MicroMaster 420 1.1kW 3-ф/380

Siemens MICROMASTER 420 — entry-level V/f drive for pumps, fans and conveyors

The MICROMASTER 420 (MM420, 6SE6420 series) is Siemens' simple, rugged workhorse for everyday duty: pumps, fans, conveyors, mixers. In our range it covers 0.7–11 kW in two supply versions — single-phase 220 V (three-phase 220 V output) and three-phase 380 V. Straight up: this series is discontinued (end of life), and Siemens' official successor is the SINAMICS G120C. So today MM420 is mostly bought as a one-for-one replacement in existing equipment where you do not want to rewrite the program or swap the whole cabinet.

What MM420 does (and does not)

This is a V/f control drive: linear V/f, quadratic V/f for pumps and fans, multi-point V/f, plus FCC (Flux Current Control) for better dynamics and efficiency. It has no vector control — full torque at zero speed and shock loads are not its job; for that use MM440 or the modern G120. Output frequency up to 550 Hz, 150% overload for 60 s (standard duty). For pressure or flow control it has a built-in PID controller (parameter P2200 and related settings) — a pump station can be closed on a sensor without a separate controller. Communication is built-in USS over RS485; PROFIBUS only via an optional module. What it does not have is Modbus RTU — worth noting if you need SCADA integration specifically over Modbus.

Where it fits

• Pumps: centrifugal, booster — quadratic V/f saves energy at partial flow.
• Ventilation and smoke extraction: soft start and speed control of duct and roof fans.
• Conveyors, transporters, mixers: where V/f is enough and zero-speed torque is not needed.
• Simple machines and auxiliary mechanisms up to 11 kW.

MM420 vs modern options

For a new project with warranty and support we usually suggest a non-EOL series — the G120C, or our Veichi range, notably the AC310 with vector control and Modbus RTU.

When MM420 is NOT the right choice

• You need torque at 0 Hz, a crane or a hoist — use a vector drive.
• You need SCADA integration over Modbus RTU — look at Veichi AC310 or G120C.
• A brand-new build — it makes more sense to install a current series than a discontinued MM420.

Our experience

Most MM420 requests we get are replacements: a drive on the line failed and the same frame size is needed without touching the settings. We match by power and supply (1-phase or 3-phase) and advise on moving to the G120C where it makes sense. If you are unsure what to fit on a specific machine, message us and we will give an honest recommendation.