EV charger surge protection for the United Kingdom starts with one voltage: the supply between two phases. At 440 V rms, our working assumption, only 82 of Walsin’s 379 varistor rows qualify, and the first rung is 460 Vac, 20 V above it. None of the 1,125 part numbers on our shelf is a varistor.
Venatech Limited, an authorised Walsin distributor in Hong Kong, wrote this from the Walsin Technology (Walsin) varistor export Walsin_MOV_ALL.xlsx (379 rows, 379 distinct part numbers) and our stock list as at 23 September 2026 (1,125 part numbers). It is for a design engineer or buyer in the United Kingdom building public or depot chargers. Every part number below is real and every count is ours. The regulation statements come from pages we fetched on 22 October 2026.
What does the UK public charge point law say that a component buyer can use?
Very little, and that is worth knowing before you spend time on it. Regulation 7 of the Public Charge Point Regulations 2023 requires a network of rapid public charge points to be reliable 99 percent of the time on average, measured over each calendar year; regulation 2 defines rapid as rated at 50 kW or more. One percent of an 8,760-hour year is 87.6 hours, our arithmetic, and it is a network average, not a per-device promise.
| Provision | What the source says | What a component buyer can use | Match / mismatch |
|---|---|---|---|
| Regulation 7 | Rapid network reliable 99% of the time on average, measured per calendar year | A reliability target for the operator | Mismatch with any part specification: no component is named |
| Regulation 2 | Rapid means a public charge point rated at 50 kW or more | Which sites are in scope | Match for scoping only |
| Regulations 5, 9 and 10 | Contactless payment, helpline, open data (section headings) | Nothing at part level | Mismatch: none names a surge or safety part |
The law sets the outcome. Surge protection is one of the ways a site avoids the downtime. Our post on choosing an MOV varistor covers the device; this post covers the voltage ladder.
Which supply voltage should a UK charger varistor be chosen against?
The highest rms voltage the varistor will see in service, and the Walsin ladder is coarse. We parsed all 379 rows of the export: 184 are rated 275 Vac or higher, which is the first rung above 253 V (230 V plus 10 percent), and only 82 are rated 440 Vac or higher, the first rung being 460 Vac. The 250 Vac rung misses 253 V by 3 V; the 420 Vac rung misses 440 V by 20 V.
We use 230 V line to neutral and 400 V line to line, each plus 10 percent, as our working assumption for a UK site. Confirm the tolerance for your connection with your network operator and your standards. The 82 rows are 6 High Energy, 34 Industrial, 24 Standard and 18 Super High Energy, over eight rungs: 460, 485, 510, 550, 575, 625, 680 and 750 Vac. We have not seen this counted anywhere: the line-to-line position has fewer than half the rows of the line-to-neutral one (82 against 184).
| Position (our assumption) | Highest rms assumed | Export rows at or above | First rung | Headroom | Match / mismatch |
|---|---|---|---|---|---|
| Line to neutral | 253 V | 184 of 379 | 275 Vac | 22 V, 8.7% | Match at 275 Vac; mismatch at 250 Vac, 3 V short |
| Line to line | 440 V | 82 of 379 | 460 Vac | 20 V, 4.5% | Match at 460 Vac; mismatch at 420 Vac, 20 V short |
The ratings are alternating-current working voltages. Our post on the D, E, V and Industrial series explains how the four series differ.
Which Walsin varistors sit on those rungs, and what differs?
One 14 mm family shows every rung with a single size held constant. SR431K14D clears 253 V and SR751K14D clears 440 V; the pair match on size and varistor tolerance and differ on working voltage, varistor voltage and nothing else in the export. The V-series twin SR751K14E doubles the exported peak current. The last column is for your incumbent part.
| Walsin part | Series | Size | Working / varistor voltage | Peak current as exported | Match / mismatch | Your incumbent |
|---|---|---|---|---|---|---|
SR391K14D |
Standard (D) | 14 mm | 250 Vac / 390 Vdc | 4,500 A | Mismatch for 253 V: 3 V short | |
SR431K14D |
Standard (D) | 14 mm | 275 Vac / 430 Vdc | 4,500 A | Match line to neutral; mismatch line to line | |
SR681K14D |
Standard (D) | 14 mm | 420 Vac / 680 Vdc | 4,500 A | Mismatch for 440 V: 20 V short | |
SR751K14D |
Standard (D) | 14 mm | 460 Vac / 750 Vdc | 4,500 A | Match line to line, 20 V headroom | |
SR751K14E |
Super High Energy (V) | 14 mm | 460 Vac / 750 Vdc | 8,000 A | Match on voltage and size; mismatch on series and peak current against the D part | |
SR821K14D |
Standard (D) | 14 mm | 510 Vac / 820 Vdc | 4,500 A | Match with 70 V headroom; mismatch on varistor voltage, 70 Vdc higher than SR751K14D |
Peak current is the export’s number, with no stated pulse waveform. A higher varistor voltage lets the protected circuit see a higher clamp, so more headroom is not free. Confirm against both datasheets and qualify in your own circuit.
Is any of this on the Hong Kong shelf?
No. We read all 1,125 part numbers in our stock list as at 23 September 2026: 0 are varistors. The list holds 864 MLCC lines, 254 chip resistor lines and seven other part numbers: three safety capacitors, two inductors, one resistor array and one 500 V MLCC.
A varistor for a UK charger is therefore a Walsin order, not a shelf pick. The ready-stock list is a dated snapshot, never live-synced, and shows what is held now.
What do Walsin’s varistor files not tell you?
Most of what a surge design needs. The export has 10 columns; Packing, SPQ and MOQ are empty on all 379 rows, there is no energy column, and we hold no varistor datasheet. The 80,000 A and 30,000 A figures in the export therefore come with no waveform, no derating curve and no lifetime pulse count.
Varistor datasheets are on our request list, not in the documents we hold. The export also gives no direct-current working voltage on any row. If your charger has a DC bus, that is a separate question for Walsin in writing.
What can a Hong Kong distributor not tell a UK charger buyer?
Anything about UK law, conformity marking or electrical safety. We hold no UK office, entity or stock; our locations are Hong Kong, Shenzhen, Singapore and Jiangmen, with Chengdu in preparation. We state no duty, customs position, transit time or carrier, and we give no legal, customs or compliance advice; confirm with your compliance team. We make no claim that any Walsin varistor is approved for a charge point.
How Venatech helps
Start with the cross-reference. Paste your incumbent varistor into the free cross-reference tool, which decodes 18 manufacturers’ part numbers across 800,000+ crossable parts and lists Walsin candidates with match and mismatch fields. For a whole charger bill of materials, use the BOM checker, up to 500 part numbers. Walsin is the only line we are authorised for; Stackpole and Viking are lines we supply. We work from Hong Kong, in small lots, and you can request a quote through the site. We offer lot and date-code traceability and a certificate of conformity per shipment on request. We hold neither ISO 9001 nor IATF 16949. The tables above came from our own export; the varistor range lists the families. Qualification stays with you.
The short version
For a UK three-phase charger, the line-to-line position cuts the Walsin varistor choice from 184 rows to 82, and the first rung, 460 Vac, leaves 20 V of headroom on our 440 V assumption. None of our 1,125 shelf part numbers is a varistor, and we hold no varistor datasheet.
Send us one varistor from your charger bill of materials and we will return the Walsin candidates with every difference stated. If your line-to-line headroom is 4.5 percent, is that the margin you meant to ship?
Sources
Fetched 22 October 2026. The regulation statements come from these pages; the part data comes from our own Walsin export and stock list.
- legislation.gov.uk, The Public Charge Point Regulations 2023 (SI 2023 No. 1168), regulation 7, reliability: https://www.legislation.gov.uk/uksi/2023/1168/regulation/7/made
- legislation.gov.uk, same instrument, regulation 2, interpretation (rapid charge point, public charge point): https://www.legislation.gov.uk/uksi/2023/1168/regulation/2/made
- legislation.gov.uk, same instrument, contents (regulations 5, 9, 10 headings): https://www.legislation.gov.uk/uksi/2023/1168/contents/made
Frequently asked questions
What does the UK charge point law say that a capacitor or varistor buyer can use?
Almost nothing at part level. Regulation 7 of the Public Charge Point Regulations 2023 sets a 99 percent average reliability for rapid points, rated 50 kW or more, over each calendar year. It names no component, so surge protection is your design choice.
How many Walsin varistor rows suit a 440 V line-to-line supply?
82 of 379 export rows are rated 440 Vac or higher, over eight rungs from 460 to 750 Vac. The first rung, 460 Vac, leaves 20 V, or 4.5 percent, on our assumption of 400 V plus 10 percent. Check your own tolerance.
Which Walsin rung clears a 230 V single-phase supply plus 10 percent?
275 Vac. The 250 Vac rung misses 253 V by 3 V. 184 of 379 rows are rated 275 Vac or higher. The 275 Vac step leaves 22 V, or 8.7 percent, of headroom on our assumption.
Does Venatech stock Walsin varistors?
No. As at 23 September 2026 none of the 1,125 part numbers on our stock list is a varistor. A varistor for a UK charger is a Walsin order. Stock moves, so ask for the current position before you plan around it.
Do you hold a Walsin varistor datasheet?
No. We hold 28 Walsin datasheets, 451 pages, and none covers varistors. The export lists voltage and peak current but no pulse waveform, energy rating or derating curve. A varistor datasheet is on our request list.
Can you advise on UK conformity or customs?
No. We hold no UK office, entity or stock and give no legal, customs or compliance advice. Confirm with your compliance team. We supply parts, lot and date-code traceability and, on request, a certificate of conformity per shipment.