MOV Energy Ratings: 40,000A vs 80,000A Industrial Varistors

A Walsin 34mm square Industrial varistor rated 40,000A carries the suffix 34R; the 80,000A version carries 34RD. The two share every voltage point — 21 matched pairs from 130Vac to 680Vac — and differ only in peak current and the one added letter. A rule that splits on the part number’s last character alone misreads all 21 pairs, because both suffixes end in a letter, not a digit.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, holds the Walsin Technology (Walsin) MOV parametric export, 379 rows, no duplicates. Every part number below is real.

What splits a 40,000A Industrial varistor from an 80,000A one?

The disc size code, not a simple grade letter. Walsin’s Industrial series covers four disc geometries — 32mm, 34mm square, 40mm and 53mm — and the 34mm square disc alone splits into two energy grades at the identical 21 voltage points:

Part number	Working voltage	Varistor voltage	Peak current	Match / mismatch
SR201K34R	130Vac	205Vdc	40,000A	Reference part
SR201K34RD	130Vac	205Vdc	80,000A	Mismatch — same voltage, 2x the peak current
SR681K34R	420Vac	680Vdc	40,000A	Match — same ladder position as SR201K34R
SR681K34RD	420Vac	680Vdc	80,000A	Mismatch — same voltage, 2x the peak current
SR112K34R	680Vac	1068.5Vdc	40,000A	Match — top of the 34R ladder
SR112K34RD	680Vac	1068.5Vdc	80,000A	Mismatch — same voltage, 2x the peak current

All 21 34R parts and all 21 34RD parts share identical working voltage and varistor voltage at every step, from 130Vac/205Vdc to 680Vac/1068.5Vdc. The only fields that differ are the trailing D and the peak current rating.

Why does a last-character filter misfile 21 parts?

Because 34R and 34RD both end in a letter, and the letter that actually carries the energy grade sits one position earlier than the last character. Split Walsin’s 101-part Industrial series on its final character and the result groups 34mm square parts by the wrong field:

Rule applied	What it produces	Correct outcome
Last character = D	32mm (19 parts, 40,000A, ends in D), 40mm (19 parts, 40,000A, ends in D), 53mm (21 parts, 70,000A, ends in D), and the 34RD parts (21 parts, 80,000A, ends in D) grouped together	Four different peak current ratings merged into one “ends in D” bucket
Last character = R	The 34R parts (21 parts, 40,000A) isolated correctly	Correct only because 34R is the one size whose code does not end in D

Reused from our published catalogue notes. The 34mm square Industrial split — 34R at 40,000A against 34RD at 80,000A — and the fact that a last-character rule misfiles 21 parts, were established and published in MOV varistor series selection: D, E, V and Industrial. This post extends that finding with a size-by-size voltage comparison across the whole Industrial series.

The reliable split is the full size code — 32mm, 34mm Square, 40mm and 53mm as Walsin’s own Size field states it — read together with the trailing D only within the 34mm square group, not across the series.

Does the voltage ladder match across all four Industrial disc sizes?

No. This is the new measurement this post adds to the banked 34R/34RD finding: the four Industrial disc sizes do not offer the same voltage steps, and the differences are not evenly distributed.

Disc size	Parts	Voltage steps	Lowest varistor voltage	Highest varistor voltage
32mm	19	19	205Vdc	1068.5Vdc
40mm	19	19	205Vdc	1068.5Vdc
34mm Square (34R + 34RD)	42	21 per suffix	205Vdc	1068.5Vdc
53mm	21	21	205Vdc	1181Vdc

The 34mm square disc adds two steps the 32mm and 40mm discs do not carry at all — 300Vdc and 950Vdc — which is why it offers 21 voltage points against their 19. The 53mm disc also offers 21 points, but a different 21: it carries 950Vdc and 1181Vdc instead of 300Vdc, and it is the only Industrial size, and the only size in the entire 379-part MOV range, that reaches 1181Vdc. No disc size offers all 22 possible voltage points that exist across the four sizes combined — every size has at least one gap.

Unique to Venatech’s data. The 300Vdc varistor voltage step exists only on the 34mm square disc, on both the 34R and 34RD suffix, and nowhere else in Walsin’s 379-part MOV extract. The 1181Vdc step exists only on the 53mm disc. A buyer who assumes the Industrial series is one ladder with four footprint options will miss both exceptions — the ladder itself changes shape between sizes.

Which disc size reaches the highest varistor voltage in the whole 379-part range?

The 53mm disc, at 1181Vdc. That is the ceiling across every series and every size in Venatech’s full MOV extract — Standard, High Energy, Super High Energy and Industrial combined. The 32mm, 40mm and both 34mm square grades all stop at 1068.5Vdc, one step short.

Disc size	Series	Peak current	Highest varistor voltage	Match / mismatch
53mm	Industrial	70,000A	1181Vdc	Highest in the 379-part range
34mm Square (34RD)	Industrial	80,000A	1068.5Vdc	Mismatch — higher current, lower ceiling voltage
40mm	Industrial	40,000A	1068.5Vdc	Mismatch — lower current, same ceiling as 34RD
32mm	Industrial	30,000A	1068.5Vdc	Mismatch — lowest current and ceiling voltage tied with 40mm

Peak current and maximum voltage do not move together across these four sizes. The 34RD disc carries more current than the 53mm disc at a lower maximum voltage, so neither figure alone tells you which part fits a given design — both have to be checked.

Does 34RD cost you anything besides a higher peak current?

Not according to the parametric export. Working voltage, varistor voltage and tolerance (±10% on all 379 parts in the file) are identical between 34R and 34RD at every one of the 21 shared points. The only field that changes is peak current, doubling from 40,000A to 80,000A. Disc thickness, lead spacing and mounting footprint are not published in this export, so any physical difference between the two grades has to be confirmed with Walsin directly.

How do I pick between the four Industrial disc sizes?

Match voltage first, then check which sizes actually offer it, then compare peak current at that voltage. Because the ladder shape changes between sizes, a design at 300Vac working voltage (470Vdc) has four candidate parts — one per size — but a design at 195Vac (300Vdc) has only two, since 32mm and 40mm skip that step entirely. Confirm the exact voltage exists on the size you want before comparing current ratings.

Do you hold a Walsin Industrial MOV datasheet?

No. Venatech holds no datasheet and no public datasheet URL for Walsin’s MOV line. This post is written from the parametric export — part number, series, size, maximum working voltage, varistor voltage, tolerance and peak current. Joule rating, clamping voltage and mounting drawing are not in that export and must be confirmed against Walsin’s own documentation.

For the full series comparison, see MOV varistor series selection: D, E, V and Industrial and How to choose an MOV varistor. The full range is on the Walsin MOV products page.

The short version

40,000A and 80,000A Industrial varistors share the same 21-point voltage ladder on the 34mm square disc and differ only in the trailing D and peak current — never split this on the last character alone. Beyond that banked finding, the four Industrial disc sizes do not share one ladder: 300Vdc exists only on 34mm square, 1181Vdc only on 53mm, and 32mm and 40mm both stop at 1068.5Vdc with 19 steps instead of 21.

Send the working voltage and the surge current you need to absorb, and Venatech Limited, an authorised Walsin distributor in Hong Kong, will return every real Walsin Industrial part that matches, by size and by voltage — not by splitting the part number on the wrong character.

Two things you can do without waiting for a reply. Cross your part — paste a single number or drop in an Excel or CSV of the whole line, and each result names what matches and what does not. And ready stock lists the varistor part numbers held in Hong Kong, with an RFQ against any of them.

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Frequently asked questions

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