Varistor Voltage From Part Number: 65 of 379 Walsin MOV Rows Disagree With Their Own Code, Checked for Germany

You cannot take the varistor voltage from a Walsin MOV part number and trust it. We decoded all 379 rows of Walsin_MOV_ALL.xlsx ourselves: 30 of 35 voltage codes match the Varistor Voltage column and 5 do not, which puts 65 of 379 part numbers at odds with their own code. We have not seen this counted anywhere.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin Technology (Walsin) metal oxide varistor parametric export of 379 rows and no varistor datasheet at all — zero of our 28 Walsin datasheets covers this line. This post is written from that one export file. Every part number below is real and every count is a count of part numbers, not pieces. For a German appliance, drive or PV inverter design, the gap below is the difference between a BOM line your tool filled in and a figure Walsin actually published.

Does Walsin’s MOV export publish a clamping voltage at all?

No. We opened Walsin_MOV_ALL.xlsx and read every one of its 10 column headers. There is no clamping voltage column, no let-through voltage column and no energy column. The ten headers are Part Number, Series, Size, Max Working Volt., Varistor Voltage, Tolerance, Peak Current, Packing, SPQ and MOQ — and the last three are empty on all 379 rows.

So the question “can I predict let-through voltage from the series” has a blunt answer in this file: you cannot predict it, and you cannot read it either. The Tolerance column reads +/-10% on all 379 rows, so it discriminates nothing. Peak Current holds 21 distinct values and is the only surge figure published anywhere in the file.

What you can work with is the varistor voltage, the number every clamping calculation starts from. It is published on all 379 rows, and it is also the number the part number claims to encode. So we audited the two against each other.

Field a surge decision needs	In the 379-row export?	Where it sits instead
Varistor voltage at 1 mA	Yes, all 379 rows	Varistor Voltage column, in Vdc
Maximum continuous working voltage	Yes, all 379 rows	Max Working Volt. column, in Vac
Peak surge current	Yes, 21 distinct values	Peak Current column, no waveform stated
Maximum clamping voltage	No column	Walsin’s own published catalogue only
Energy rating in joules	No column	Walsin’s own published catalogue only
Derating curve	No column	Walsin’s own published catalogue only

Can I read the varistor voltage off a Walsin MOV part number?

On 314 of 379 rows, yes. On 65, no. We parsed the three digits after the SR prefix on every part number in the file and decoded them as the usual two-significant-figures-plus-multiplier convention — 180 as 18 Vdc, 681 as 680 Vdc, 361 as 360 Vdc. Thirty of the 35 distinct codes land exactly on the Varistor Voltage column. Five do not, and because each voltage step carries up to 17 footprints, those five codes account for 65 of the 379 part numbers, 17.2% of the line.

Part number	Code	Code decodes to	Varistor Voltage column	Match / mismatch
SR181K05D	181	180 Vdc	180 Vdc	Match — code and column agree
SR361K14D	361	360 Vdc	360 Vdc	Match — code and column agree
SR431K14D	431	430 Vdc	430 Vdc	Match — code and column agree
SR201K05D	201	200 Vdc	205 Vdc	Mismatch — column is 2.44% above the code
SR271K20D	271	270 Vdc	283 Vdc	Mismatch — column is 4.59% above the code, the widest in the file
SR561K14D	561	560 Vdc	580 Vdc	Mismatch — column is 3.45% above the code
SR112K53D	112	1100 Vdc	1068.5 Vdc	Mismatch — column is 2.95% below the code, and non-integer
SR122K53D	122	1200 Vdc	1181 Vdc	Mismatch — column is 1.61% below the code; one part only

Three codes read low against the column and two read high. That matters more than the size of the error: a decoder cannot be corrected with a single offset, because the sign flips at the top of the range.

Which five voltage codes disagree with the column, and by how much?

Five codes, 65 rows, and the damage is not spread evenly. We grouped the 65 by voltage step. Three steps — 130 Vac, 180 Vac and 360 Vac — carry 17 part numbers each across all 11 footprints, so a decoder is wrong on every footprint at those three steps. The 680 Vac step carries 13 rows across 9 footprints. The 750 Vac step carries exactly one part, SR122K53D, the 53 mm Industrial disc.

Working voltage step	Code	Code decodes to	Column reads	Rows affected	Footprints affected
130 Vac	201	200 Vdc	205 Vdc	17	11 of 11
180 Vac	271	270 Vdc	283 Vdc	17	11 of 11
360 Vac	561	560 Vdc	580 Vdc	17	11 of 11
680 Vac	112	1100 Vdc	1068.5 Vdc	13	9 of 11
750 Vac	122	1200 Vdc	1181 Vdc	1	1 of 11

All four series are hit. We counted the 65 by series: 22 Standard (D Series), 21 Industrial, 12 Super High Energy (V Series) and 10 High Energy (E Series). There is no series you can select into to avoid the problem, and no footprint either — the 34 mm square Industrial part SR201K34RD is in the 65 just as much as the 5 mm Standard part SR201K05D.

Does the series tell you the working-voltage to varistor-voltage ratio?

It narrows it and it does not fix it. We computed the ratio of maximum working voltage to varistor voltage on all 379 rows. Across the file it runs from 0.588 on the 40 Vac / 68 Vdc pair to 0.667 on the 120 Vac / 180 Vdc pair — a 13.4% spread. That much we have published before, in the Sweden post, and we re-measured it for this one.

What is new is the split by series. The High Energy, Super High Energy and Industrial series have an identical ratio window: 0.6044 to 0.6500, on every one of their rows. The Standard (D Series) window is wider at both ends, 0.5882 to 0.6667, and both extremes sit on steps the Standard series owns alone.

Part number	Series	Max working voltage	Varistor voltage	Ratio	Match / mismatch vs the 0.6044–0.6500 energy-series window
SR680K05D	Standard (D Series)	40 Vac	68 Vdc	0.5882	Mismatch — below the window; no energy-series part exists at 40 Vac
SR181K05D	Standard (D Series)	120 Vac	180 Vdc	0.6667	Mismatch — above the window; no energy-series part exists at 120 Vac
SR431K05D	Standard (D Series)	275 Vac	430 Vdc	0.6395	Match — inside the window
SR431K34RD	Industrial	275 Vac	430 Vdc	0.6395	Match — same step, same ratio, 200x the peak current
SR112K53D	Industrial	680 Vac	1068.5 Vdc	0.6364	Match on ratio, mismatch on code — 112 decodes to 1100 Vdc

We have not seen this counted anywhere: 13 of the 35 voltage steps in Walsin’s varistor export are Standard-series only, they sit from 11 Vac to 120 Vac, and they contain both the highest and the lowest working-to-varistor ratio in the whole file. Above 120 Vac the ratio is penned into a 7.5% band. Below it, it is not.

Knowing the series tells you the ratio to within 7.5% above 130 Vac and tells you nothing below it. In neither case does it tell you the let-through voltage, because that figure is not in the file. The series decode is in MOV varistor series selection: D, E, V and Industrial, and the footprint-by-voltage census is in the MOV voltage ladder.

What does the mismatch do to a 230 Vac German mains design?

It lands on the step most likely to be chosen, and we checked which one. A 230 Vac German mains input is normally protected by a varistor rated 275 Vac or 300 Vac to clear the supply tolerance. Those two steps decode cleanly: 431 is 430 Vdc and 471 is 470 Vdc, and the column agrees on all 34 parts.

The trap is one step down. A designer reading the export for a 180 Vac rail — a rectified intermediate, a motor winding, a 110 Vac variant — hits code 271. The code says 270 Vdc. The file says 283 Vdc. The ±10% tolerance in the file is applied to 283 Vdc, not to 270. The same happens at 130 Vac, where 201 says 200 Vdc against 205 Vdc, and at 360 Vac, where 561 says 560 Vdc against 580 Vdc.

What should a German engineer do before qualifying a Walsin varistor?

Three steps, and the first costs five minutes. Read the Varistor Voltage column rather than the part number, on every line — not just the five codes above, because a future code could join them. Then get the approval sheet for the exact part number, because clamping voltage, joules and the derating curve are not in any file we hold.

1. Take the varistor voltage from the column, never from the code. On 65 of 379 rows they disagree, and the sign of the error flips between 360 Vac and 680 Vac.
2. Cross the whole input stage in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross reference tool, filter by commercial or automotive grade, and read every stated difference rather than a claimed match. We will not tell you a part is equivalent. We will show you where it differs.
3. Check what was physically in Hong Kong on ready stock — a dated snapshot as at 23 September 2026, not a live feed. Both the varistor and the disc capacitor lines had zero part-number representation in that snapshot, so a varistor is an order, not a pull.

The full line sits on the Walsin MOV and varistor page.

The short version

Walsin’s varistor export publishes no clamping voltage, no joules and no derating curve, so let-through voltage cannot be predicted from the series or read from the file. What the file does publish is a varistor voltage on all 379 rows, and the part number agrees with it on 314 and disagrees on 65. Five codes are responsible: 201, 271, 561, 112 and 122. Three read low, two read high, and 271 is the worst at 4.59%. All four series and all eleven footprints are affected. The working-to-varistor ratio is 0.6044 to 0.6500 across every High Energy, Super High Energy and Industrial row, and 0.5882 to 0.6667 across Standard — both extremes on the 13 steps the Standard series owns alone. We hold no varistor datasheet. Qualification stays with you.

Send us the varistor lines off your German bill of materials and we will tell you, part number by part number, whether the code and the column agree — and what we would have to ask Walsin for on your behalf. If your BOM system populated a varistor voltage by parsing the part number, go and check the 65. We would like to know how many designs that has reached.

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Frequently asked questions

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