The Disc Capacitor UR Column Holds Two Incompatible Rating Systems

We parsed all 929 rows of Walsin’s disc capacitor export. The UR column mixes two rating systems: 562 rows carry a bare DC figure, 367 carry a compound AC safety rating, and zero of the 929 parse as a number. A safety capacitor voltage rating is the one field a submission turns on, and here it will not sort.

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50Vdc is a number with a unit. X1-500Vac/Y1-500Vac 1500Vdc is three numbers, two safety classes and a withstand figure in one cell. Sorting the column puts them in one list and implies they are comparable.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds all 203 of Walsin Technology (Walsin) parametric export files. This post is measured from one of them, Walsin_DiscCap_ALL.xlsx, and from the Venatech ready stock snapshot as at 23 September 2026. Every part number below is real and every count is of part numbers, not pieces.

What is actually in the UR column of Walsin’s disc capacitor export?

Fifteen distinct strings across 929 rows, in two incompatible formats. We read every unique value. Seven are bare DC ratings — 50Vdc, 100Vdc, 500Vdc, 1000Vdc, 2000Vdc, 3000Vdc and 6000Vdc. The other eight are compound AC safety ratings that name an X class, a Y class and sometimes a DC withstand figure in the same cell. Thirteen distinct voltage magnitudes are embedded across those fifteen strings, and a single cell can hold one, two or three of them.

UR string	Rows	Numbers in the cell	Rating system
50Vdc	109	1	Bare DC working voltage
1000Vdc	106	1	Bare DC working voltage
100Vdc	103	1	Bare DC working voltage
2000Vdc	100	1	Bare DC working voltage
500Vdc	87	1	Bare DC working voltage
3000Vdc	41	1	Bare DC working voltage
6000Vdc	16	1	Bare DC working voltage
X1-440Vac/Y2-250Vac	57	2	AC safety, X1 and Y2 classes
X1-440Vac/Y2-300Vac	57	2	AC safety, X1 and Y2 classes
X1-400Vac/Y1-250Vac	56	2	AC safety, X1 and Y1 classes
X1-400Vac/Y1-400Vac	56	2	AC safety, X1 and Y1 classes
X1-500Vac/Y1-500Vac 1500Vdc	54	3	AC safety plus a DC figure
X1-500Vac/Y2-500Vac 1500Vdc	49	3	AC safety plus a DC figure
X1-440Vac/Y2-300Vac 1500Vdc	23	3	AC safety plus a DC figure
X1-760Vac/Y1-500Vac	15	2	AC safety, X1 and Y1 classes

We have not seen this split counted anywhere. The two systems are not two notations for one quantity. A bare DC figure is a working voltage. An X1/Y2 pair is two mains-classification limits with creepage, clearance and failure-mode consequences attached, and the Y class decides whether the part may bridge a mains barrier at all.

How many rows sit in each rating system?

562 in the DC system and 367 in the AC safety system — a 60/40 split, not a handful of exceptions. We grouped the rows: the 562 DC rows are Class I Temperature Compensation (182), Class II HI-K (333), Low Dissipation (29) and Low Dissipation lead-free (18). The 367 AC rows are all in the ten Safety Certificated Caps series, split 181 to the X1/Y1 AH and AS families and 186 to the X1/Y2 AC family. Within the AC set, 126 rows append a 1500Vdc figure in three of the eight formats and 241 do not.

Rating system	Rows	Distinct UR strings	Series behind them	Match / mismatch vs a numeric voltage column
Bare DC working voltage	562	7	Class I, Class II HI-K, Low Dissipation	Match on shape — one number, one unit, sorts correctly
AC safety, no DC figure	241	5	Safety Certificated AH, AC and AS	Mismatch — two numbers and two class letters in one cell
AC safety plus DC withstand	126	3	Safety Certificated AH 500V, AC 500V, AC Auto	Mismatch — three numbers, mixed units, mixed meaning
Whole export	929	15	14 series	Mismatch — no single parse reads all 929 rows

Does any numeric parse work on this column?

None. We ran the obvious ones. A plain float() on the raw cell succeeds on 0 of 929 rows, because every value carries a unit suffix. A regular expression for “digits, then V, then dc or ac” reads 562 rows and fails 367. Taking the first number in the cell reads all 929 and gets 126 of them wrong by returning an X1 figure where a Y-class figure decides the application. Taking the largest number returns 1500 for 126 safety parts whose actual AC working rating is 440 or 500 Vac.

So no parse is both complete and correct. That is a stronger statement than “the column is messy”. A messy column can be cleaned with a rule. This one needs a decision about which of two or three numbers is the rating, and that depends on which barrier the part sits across — information in no column of the export.

What happens when a BOM tool imports these 929 rows?

One of three failures, and all three are silent. We have tested the behaviour against our own extract. A tool with a numeric voltage field rejects 367 rows outright, so the entire safety range disappears from the import and the user sees a shorter list, not an error. A tool that coerces and defaults writes a null or a zero into 367 rows, which then fail any “rated voltage ≥ 250 V” filter. A tool that takes the first integer writes 440 or 500 for a part whose Y-class limit is 250 or 300 Vac — the one case that is worse than dropping the row, because the number looks plausible.

YP0AC101K060 is a 100 pF X1/Y2 part reading X1-440Vac/Y2-250Vac. YP1AC101K060 is the same capacitance in the same series reading X1-440Vac/Y2-300Vac. Both import as “440” under a first-integer rule, and the field that distinguishes them — 250 versus 300 Vac on the Y side — is the one a mains design cares about. YP1AC101K060 is also the part we have previously flagged as an X1/Y2 code pointing at the X1/Y1 datasheet, so it fails twice in two different ways.

Why are the AC-rated parts exactly the ones a safety submission depends on?

Because the 367 unparseable rows are the whole Class X and Class Y range, and nothing else in the export does that job. A Y capacitor bridges a mains barrier to earth; an X capacitor sits line to line. Those are the parts an approval body looks at and the parts whose datasheet a notified body asks for by name. The 562 rows that parse cleanly are general-purpose DC disc capacitors that no safety submission turns on.

We have measured the class structure before and re-confirmed it here: the Y class available to you is decided by the X1 rating. At X1 400 Vac the export offers Y1 only, on 112 rows. At 440 Vac, Y2 only, on 137. At 500 Vac, both — 54 rows Y1 and 49 Y2. At 760 Vac, Y1 only, on 15 rows, and YP0AS101K070 is one of them. A tool that collapses the cell to a single number destroys exactly that relationship.

What does one 100 pF line look like across all fifteen rating strings?

It looks like 38 parts. We pulled every row at exactly 100 pF: 38 part numbers, spanning all fifteen UR strings and 14 of the 15 disc series. One BOM line reading “100 pF ceramic disc capacitor” therefore resolves to a set that contains both rating systems, five dielectric labels and every X and Y class Walsin offers. There is no voltage sort that separates them, because the sort key is not a number. We will not tell you a part is equivalent. We will show you where it differs.

Part number	Series	Dielectric	Tolerance	UR as written	Match / mismatch vs 100 pF Y2 class, 250 Vac
YP0AC101K060	Safety Certificated X1/Y2 AC	YP(Y5P)	+/-10%	X1-440Vac/Y2-250Vac	Match on capacitance, Y2 class and 250 Vac
SL0AC101J090	Safety Certificated X1/Y2 AC small size	SL	+/-5%	X1-440Vac/Y2-250Vac	Match on class and rating; mismatch — SL dielectric, ±5%
YP1AC101K060	Safety Certificated X1/Y2 AC	YP(Y5P)	+/-10%	X1-440Vac/Y2-300Vac	Match on Y2 class; mismatch — 300 Vac Y side, not 250
YP5AC101K060	Safety Certificated X1/Y2 AC 500V	YP(Y5P)	+/-10%	X1-500Vac/Y2-500Vac 1500Vdc	Match on Y2 class; mismatch — 500 Vac and a third figure in the cell
YP0AH101K060	Safety Certificated X1/Y1 AH	YP(Y5P)	+/-10%	X1-400Vac/Y1-250Vac	Match on 250 Vac; mismatch — Y1 class, different barrier rules
YP0AS101K070	Safety Certificated X1/Y1 AS	YP(Y5P)	+/-10%	X1-760Vac/Y1-500Vac	Mismatch — Y1 class, 760 Vac X side, 500 Vac Y side
YP500101K040	Class II HI-K	Class II YP(Y5P)	+/-10%	50Vdc	Mismatch — no AC rating and no safety class at all
SL602101J090	Class I Temperature Compensation	Class I SL	+/-5%	6000Vdc	Mismatch — 6,000 Vdc and still not a Y capacitor
LR102101K050	Low Dissipation	Y5R	+/-10%	1000Vdc	Mismatch — DC rating only, different dielectric family

SL602101J090 is the row that makes the point hardest. Its UR cell reads 6000, the largest number in the whole column, and it is not a safety capacitor. Any tool that ranks candidates by rated voltage puts it at the top of a Class Y search.

Do we hold a disc capacitor datasheet to confirm any of this?

No. We hold 28 Walsin datasheets, 451 pages — 26 MLCC and two chip resistor sheets. For the disc capacitor line we hold zero. So every figure above is the export’s own value, and we cannot confirm from any document in our library what the 1500Vdc on 126 rows is measuring, whether it is a working voltage or a withstand figure, or what the AC ratings are at any temperature other than the one the sheet would state.

We have been caught by exactly this before and corrected it: on the chip safety series the export’s “Rated Voltage” field turned out to be the impulse voltage, while the real working voltage appeared nowhere in the data. That correction is published, and it is why we now refuse to describe a rating from an export when we hold no sheet.

Where we can be checked, we are. UL file E182369 covers Walsin’s safety capacitor line and is searchable in UL’s own public database in about thirty seconds. Ask us for the certificate scope that covers your part number and it goes to your inbox. We will tell you what we do not hold. Most distributors will not.

What should a buyer in Germany or the United States do about it?

Treat the UR cell as text and read all of it. We checked the dated snapshot as at 23 September 2026: of its 1,125 catalogue codes, not one is a disc capacitor, so disc parts are an order-in line and the lead time conversation starts earlier. The trade press reported passive component lead times stretching through 2026 as AI server and electric vehicle programmes drew on the same capacity.

1. Specify the Y class and the Y voltage separately from the X figure. “Y2, 250 Vac” is a requirement. “440 V” is what a parser produced, and 137 rows will match it while offering a Y side of 250 or 300 Vac.
2. Cross the whole BOM in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross-reference tool. It is matched against Walsin’s published catalogue and returns candidates field by field, with every difference from your original stated rather than hidden. The safety-certified filter is one of the special-requirement filters on that page.
3. Check what is physically in Hong Kong on ready stock before you commit to a slot. It is a dated snapshot as at 23 September 2026, not a live feed.

For what separates the two Y classes, see X1/Y1 vs X1/Y2 safety capacitors. For the export field we previously found to be an impulse figure, see safety capacitor rated voltage: 173 rows read 5000Vdc. For the certificates you can check without asking us, see five safety capacitor certificate numbers. The range is on the Walsin disc capacitor page.

The short version

The UR column in Walsin’s disc capacitor export is not a voltage field. It is a text field holding two rating systems: 562 bare DC figures and 367 compound AC safety strings, in fifteen formats carrying one, two or three numbers each. No numeric parse reads all 929 rows correctly — float() reads zero, a DC pattern reads 562, first-integer reads all 929 and mis-states 126. The rows that break are the entire Class X and Class Y range, which is the part a safety submission depends on. One 100 pF line resolves to 38 parts across all fifteen strings. We hold no disc capacitor datasheet, so every figure here is flagged. Qualification stays with you.

Send us the safety capacitors off your BOM with the Y class and the Y-side voltage stated separately, and we will come back with Walsin candidates field by field, differences included — and tell you plainly which figures we cannot confirm because we hold no sheet. If your BOM tool imported a disc capacitor as “440 V”, we would like to see what it did with the other two numbers in the cell.

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Frequently asked questions

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