Walsin Inductors for Italian Appliance and Motor Drive Design: Reading the Real DCR Ladder

Before an Italian appliance or motor drive design can rank Walsin inductors on conduction loss, the DC resistance column has to be unit-corrected. Walsin Technology (Walsin) writes it three ways across 5,410 real part numbers: 4,892 rows in ohms, 341 in milliohms and 177 with no unit at all. We counted every row. Sort the bare numbers and the ladder inverts.

---

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds Walsin’s inductor parametric export: 5,411 rows, of which one is a QA test artefact and 5,410 are real parts. We hold no Walsin inductor datasheet. Every figure below is counted from that export with the test row excluded, every part number is real, and counts are of part numbers rather than pieces. Specification figures here describe what the export prints, not what a datasheet guarantees.

Does Venatech have an Italian entity or Italian stock?

No. The group’s operating entities are Venatech Limited in Hong Kong, the Shenzhen trading company, VENATECH PTE LTD in Singapore and the Jiangmen factory in Guangdong, with Chengdu in preparation. There is no Italian entity, no Italian warehouse, no Italian-held inventory and no local sales office. Everything ships from Hong Kong.

Italian white goods and appliance electronics is a real concentration of inductor demand — compressor and drum motor inverters, induction hob drivers, brushless pump controllers — and those boards run inductors in two distinct roles. A µH-class power inductor carries the control rail. A nH-class chip inductor or ferrite part handles conducted emissions. The two roles are ranked on different numbers, and both depend on DC resistance being read correctly.

Why does Walsin’s inductor DC resistance column need a unit check first?

Because the unit is inside the cell, not in the header, and it changes row to row. The RDC column stores a string: 0.045Ω, 20mΩ, or on some rows a bare 0.07 with nothing after it. Across the 5,410 real part numbers the split is exact:

RDC notation in the export	Part numbers	Share	Match / mismatch for a numeric sort
Ends in Ω — ohms	4,892	90.4%	Match — reads correctly once the symbol is stripped
Ends in mΩ — milliohms	341	6.3%	Mismatch — 1,000× too large if the symbol is stripped
No unit character at all	177	3.3%	Mismatch — no way to tell which scale applies from the cell

The 177 unit-less rows are not scattered. 172 of them are the MCI-TM series and the other five are the WLPN series. That is the whole set, and it is easy to miss because the values look plausible either way: MCI0603TM1N0BHBP exports 0.1 and WLPN202012N1R0PB exports 0.07.

The 341 milliohm rows are the dangerous ones, and here is why in one number. Every single one of the 341 milliohm figures is a bare value greater than 1 — they run from 1.8 to 3800. The ohm rows run from 0.004 to 3800. So the moment you strip the unit symbol and sort ascending, all 341 milliohm parts land above every genuinely sub-ohm part in the catalogue, and the lowest-loss inductors in the range appear at the bottom of the list.

Our published work on reading RDC covers why DC resistance decides the choice at all, and the unit trap in the Inductance column. The measurement in this post is a different one: the RDC column has the same disease, and we have now counted it.

Which Walsin series write DC resistance both ways?

Eight of the 47 series, holding 2,824 part numbers between them. This is the measurement we established for this post.

Series	Rows in ohms	Rows in milliohms	Match / mismatch within the series
WLCW Series	740	51	Mismatch — and both notations appear in one case size
WCI Series	688	32	Mismatch — splits cleanly on case size
WCA Series	612	10	Mismatch — splits cleanly on case size
WQCW Series	559	10	Mismatch — splits cleanly on case size
WQPH Series	8	12	Mismatch — splits cleanly on case size
WPA Series	8	12	Mismatch — splits cleanly on case size
WLBD(HC) Series	70	1	Mismatch — and both notations appear in one case size
MHC-P Series	10	1	Mismatch — and both notations appear in one case size

In five of those eight the notation at least follows a rule: the physically largest case size in the series is written in milliohms and every smaller size is written in ohms. WQPH is the clearest example — all eight 2016(0806) rows use ohms, all twelve 2520(1008) rows use milliohms, and no case size carries both.

In three series the rule breaks. WLCW, WLBD(HC) and MHC-P each have one case size that carries both notations at once. The worst is WLCW at 2012(0805): 161 rows in ohms and 21 rows in milliohms, same series name, same case size. There is nothing in the series, size, inductance or tolerance fields that tells you which notation a given row will use.

What does that do to a real appliance DCR ladder?

It hides the better part. Take 5.6 nH in a 2012(0805) WLCW package — the sort of value that sits in a conducted-emissions filter on an appliance control board. Two real part numbers cover it, and the export writes their DC resistance on different scales.

Part number	Series	Case	Inductance	Tolerance	RDC as exported	RDC in ohms	Rated current	Q Min	Match / mismatch
WLCW2012HQJ5N6PB	WLCW	2012(0805)	5.6 nH	±5%	35mΩ	0.035 Ω	1.6 A	98	Match on value and case — less than half the DC resistance
WLCW2012Z0J5N6PB	WLCW	2012(0805)	5.6 nH	±5%	0.08Ω	0.080 Ω	600 mA	65	Mismatch — 2.3× the loss, 37% of the current
WLCW2012HQG12NPB	WLCW	2012(0805)	12 nH	±2%	45mΩ	0.045 Ω	1.6 A	80	Match on value and case — lower loss of the pair
WLCW2012Z0G12NPB	WLCW	2012(0805)	12 nH	±2%	0.15Ω	0.150 Ω	600 mA	50	Mismatch — 3.3× the loss, 37% of the current
WLCW2012HQJ51NPB	WLCW	2012(0805)	51 nH	±5%	120mΩ	0.120 Ω	1 A	65	Match — still the HQ stem, still milliohms
WLCW2012HQJ2N5PB	WLCW	2012(0805)	2.5 nH	±5%	20mΩ	0.020 Ω	1.6 A	80	Match — lowest DC resistance in the 2012 WLCW set

Both 5.6 nH parts are the same series, the same case size, the same nominal value and the same ±5%. The HQ stem part has 0.035 Ω and is rated 1.6 A. The Z0 stem part has 0.080 Ω and is rated 600 mA. In a motor drive control rail the conduction loss term goes with the square of current, so on paper that is a materially different part — and a tool that sorted on the bare number would have put 35 behind 0.08 and recommended the wrong one.

The same inversion happens at 12 nH, where the better part reads 45 against the worse part’s 0.15.

How do I build a usable DCR ladder for an appliance control rail?

Normalise the unit first, then rank. Three rules cover the whole line. Treat a trailing mΩ as a divide by 1,000. Treat a Ω as ohms as written. And for the 177 unit-less rows — all of them MCI-TM or WLPN — do not guess: ask, because nothing in the cell distinguishes 0.07 Ω from 70 mΩ, and those happen to be the same number.

For the µH power inductors that carry an appliance control rail, the WQPH 2520(1008) ladder is a clean example once normalised, and it is the family where the milliohm notation applies:

Part number	Inductance	RDC as exported	RDC in ohms	Rated current	Match / mismatch for a 2 A control rail
WQPH252012MR47PS	0.47 µH	16mΩ	0.016 Ω	5.8 A	Match — most current headroom, lowest loss
WQPH252010MR33PS	0.33 µH	17mΩ	0.017 Ω	5.6 A	Match — thinner package, similar loss
WQPH252012M1R0PS	1.0 µH	36mΩ	0.036 Ω	3.9 A	Match — more inductance for less ripple
WQPH252012M4R7PS	4.7 µH	160mΩ	0.160 Ω	1.8 A	Mismatch — rated below the 2 A rail
WQPH201610MR33PS	0.33 µH	0.021Ω	0.021 Ω	4.7 A	Match — but note the notation changed with the case size
WQPH201610M4R7PS	4.7 µH	0.24Ω	0.240 Ω	1.3 A	Mismatch — rated below the 2 A rail

Note the last two rows. They are the same series as the first four and their DC resistance is printed in ohms, because they are the smaller 2016(0806) case. A ladder that mixes case sizes in one series also mixes notations.

Rated current here is a thermal figure and the export states no ambient for it, so the 2 A column is a data comparison and not a design verdict. For the current question specifically, see our power inductors above 1 A post.

What does Venatech add for an Italian appliance programme?

Work a search box cannot do. Walsin’s own parametric search will show you the RDC cell; it will not tell you that 341 of 5,410 rows are on a different scale, that 177 carry no scale at all, or that eight series use both under one name. We counted that, and we normalise the unit before we return a ladder.

Our cross-reference tool returns a field-by-field comparison with the differences named. We will not tell you a part is equivalent. We will show you where it differs — and on this line one of the things that differs is the unit the number is printed in. The full catalogue is on the Walsin inductor range page.

The short version

Unit-correct the RDC column before you rank anything. 4,892 of 5,410 rows are in ohms, 341 in milliohms and 177 carry no unit. All 341 milliohm values are bare numbers above 1, so a naive sort inverts the ladder. Eight series use both notations and three of those mix them inside a single case size — WLCW at 2012(0805) has 161 ohm rows against 21 milliohm rows. We hold no Walsin inductor datasheet, so confirm every figure against Walsin’s own document.

Send the inductor lines from your appliance or motor drive BOM and we will return a unit-normalised DCR and rated-current ladder, with the rows whose unit we cannot resolve marked as unresolved rather than guessed. Qualification stays with you. Ready stock shows what is physically in Hong Kong as a dated snapshot.

---

Frequently asked questions

---

---

Three ways to get this answered today

1. Cross a part, free. Paste up to 500 part numbers, or drop an Excel or CSV file, 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. Filter by commercial or automotive grade, or for soft termination, high temperature, safety certified, high Q / low ESR or low profile. There is no login and no charge.

2. Send the whole BOM. Upload a BOM and request a quote and we will come back line by line — including the lines we cannot help with, which is usually the more useful half of the answer.

3. Check the shelf before you commit. Ready stock shows what was physically in Hong Kong as at 23 September 2026. It is a dated snapshot, never a live feed, and quantities are never permanent.

Why take our word for any of this? Don’t — check it.

Venatech Limited (威納電子有限公司) is an authorised Walsin Technology distributor in Hong Kong. Confirm that with Walsin rather than with us. On the safety capacitor series we hold UL file E182369, which is searchable in UL’s own public database, together with TUV certificates R50381780 and R50195920 and CQC CQC20001280137 and CQC20001280136, against EN 60384-14:2023, IEC 60384-14:2023 and UL 60384-14. We hold 28 Walsin datasheets, 451 pages, and we will send the one covering your part number. Shipments arrive in original sealed Walsin packaging with lot and date-code traceability, and a certificate of conformity is available per shipment on request.

We will also tell you what we do not hold, which no competitor publishes. REACH, SVHC, conflict minerals, PFAS, China RoHS, ISO 9001, IATF 16949, PPAP, IMDS and a Declaration of Conformity appear nowhere in those 451 pages. You would rather hear that from us now than from your own supplier-approval team later. AEC-Q200 is compliant in Walsin’s own words and never certified, we hold no manufacturer’s end-of-life or allocation list for any brand, and qualification in your own circuit stays with you. We will not tell you a part is equivalent. We will show you where it differs.

Venatech Limited · Unit 207, 2/F, Sun Ling Plaza, 30 On Kui Street, Fanling, N.T., Hong Kong · (852) 2628 4777 · Hong Kong, Shenzhen, Singapore and Jiangmen, with Chengdu in preparation.