Siemens / Drives / MICROMASTER 420

Every MICROMASTER 420 article number, 0.12 kW to 11 kW, filtered and unfiltered. Plus how to read the number off a dead drive.

The MICROMASTER 420 is discontinued. It is also still running conveyors, pumps, fans and machine tools across New Zealand, and it fails often enough that replacement is a regular job rather than a rare one.

We supply used and surplus MM420 drives, and we can quote the SINAMICS G120 successor if you would rather migrate. Send the number off the label.

How to read a MICROMASTER number

The article number tells you almost everything. Take 6SE6420-2UD22-2BA1.

Filter letter. U means no filter. A means internal EMC filter Class A. B means internal filter Class B.

Voltage letter. B is 1 AC 200 to 240 V. C is 1 AC or 3 AC 200 to 240 V. D is 3 AC 380 to 480 V.

Power code. The first digit is a multiplier. 1 means times 0.1, 2 means times 1, 3 means times 10, 4 means times 100. The rest reads as a decimal. So 17-5 is 0.75 kW, 22-2 is 2.2 kW, 31-1 is 11 kW. A few round rather than match exactly.

Frame size letter. A, B or C on the 420, ascending with power. This tells you whether a replacement will fit the existing panel cutout.

MICROMASTER 420, 1 AC 200 to 240 V

MICROMASTER 420, 3 AC 200 to 240 V

The same 6SE6420-2UC article number covers both single-phase and three-phase 200 to 240 V supplies on the smaller ratings. That is not a catalogue error.

MICROMASTER 420, 3 AC 380 to 480 V

The most common supply in New Zealand industry.

Frame sizes and dimensions

Fitting a communication module adds 23 mm to the depth.

Every MICROMASTER ships without an operator panel

The 420 comes with a Status Display Panel only. A BOP or AOP is a separate order, and the same panel works across several MICROMASTER series.

If you have loose panels or modules from a scrapped drive, they are worth something. See our Sell To Us page.

Three things worth knowing before you buy

Filtered drives cannot go on an IT supply

Siemens states plainly that MICROMASTER inverters with an internal filter are not permitted on non-grounded IT mains supplies. If your site runs an IT system, order the unfiltered version. Getting this wrong destroys the drive.

The Y capacitor

On a non-grounded supply the removable Y capacitor must be taken out and an output choke fitted. This is a documented Siemens procedure, not a workaround.

Residual current devices

Leakage currents on these drives, with or without a filter, may exceed 30 mA. Typical values in practice are 10 to 50 mA depending on design, environment and cable length. Trouble-free operation on a 30 mA RCD cannot be guaranteed. A 300 mA device is workable.

Why is my drive tripping?

Motor cable length is a common cause. Without an output choke the MM420 is limited to 50 m shielded or 100 m unshielded. With the right choke that extends to 200 m shielded or 300 m unshielded.

Replace or migrate

If the line is down today, a used or surplus MM420 of the same article number is the fastest route back to running. No reprogramming, no panel changes.

If you are planning ahead, the SINAMICS G120 is the current equivalent and we can quote it as a distributor. It is not a drop-in, so treat it as a project. We can supply the new drives, keep the old ones running through the changeover, and take the decommissioned units away afterwards.

Send us your article numbers

One drive or a full site list. We will come back with price, condition and lead time. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Siemens AG. All trademarks, brand names and article numbers are the property of their respective owners and are used here for identification purposes only.