RC suppressor for the coil on a Schneider Act9 iCT 25A 240v AC Contactor  - Page 1
Forum section: electronics / general

author: hazzer
author_rank: Regular Contributor
timestamp: July 26, 2025, 08:08:18 pm
content: I need an RC suppressor for the coil in a Schneider contactor type A9C21732https://www.se.com/uk/en/product/A9C21732/ict-25a-2no-230-240v-50hz-mo-contact/It looks to have metal tabs on the side to connect up to A1, A2, (the coil connections) but for the life of me I can't find any info on the Schneider website to suggest they supply an RC network...Q..... am I just best to jury rig a series 100R and X class 220nF (coil is about 3VA )I'll post here on the chance someone has used a similar contactorPS tried the Schneider AI chat bot .....Bot: <AIGeneratedText> Based on the provided information, the compatible suppressor for A9C21732 is **A9A27062**. This product is listed under the 'ACCESSORIES' category and is marked as 'Compatible' with A9C21732.....Sadly **A9A27062** is a spacer plate!Harry

author: MF-jockey
author_rank: Regular Contributor
timestamp: July 27, 2025, 09:37:27 am
content: Please search for Schneider Electric A9C15920 (very expensive)

author: hazzer
author_rank: Regular Contributor
timestamp: July 27, 2025, 11:59:58 am
content: Thanks - yes that is expensive, very tempted to just knock something up...a quick Qspice model suggests 10K 1W and 100nF rated at main voltage...I think that's the way to go.Thanks for the suggestion.H

author: hazzer
author_rank: Regular Contributor
timestamp: July 27, 2025, 12:25:51 pm
content: Good old RS not one to price gouge.... much.... 130 euro.... FFS

author: Seekonk
author_rank: Super Contributor
timestamp: July 30, 2025, 10:28:00 pm
content: A company I used to work for manufactured suppressors. Nothing we made ever approached 10K ohm. 220 ohm was our highest resistance.

author: hazzer
author_rank: Regular Contributor
timestamp: August 02, 2025, 08:22:37 pm
content: Thanks yes it is very high value, I've a "used" A9C15920 on order from a well know auction site, I post later once it arrives..

author: floobydust
author_rank: Super Contributor
timestamp: August 02, 2025, 08:43:58 pm
content: What I typically see on contactors is a MOV across the coil.I think a snubber has to be placed across the "switch", whatever is switching the contactor's coil power.Across the coil is not as effective and there is the risk of resonance. Very hard to design in because the inductance/current shifts greatly once the contactor pulls in.

author: hazzer
author_rank: Regular Contributor
timestamp: August 03, 2025, 10:26:33 am
content: Thanks, yes this seems to have a touch of the black arts about it, I was considering a MOV but concerned it would eventually wear out, the contactor will be switching several times a day, the simulation cct is simplistic but it seems to show an optimum value for R in the RC of twice the resistance in the contactor coil, lower values also work but with additional ringing... I might resort to bench testing and scope it to see if it behaves as the model suggests

author: floobydust
author_rank: Super Contributor
timestamp: August 03, 2025, 07:49:36 pm
content: In real life, a contactor is a tough load. Inrush current is quite high, inductance increases a lot when the armature pulls in. Then there is residual magnetism back-EMF as the armature moves fast away from the coil. You can prove it all looking with a scope.I would not use a snubber across the coil. Note the A9C15920 is intended for protecting the AUX contacts. So it would connect across those switches.

author: hazzer
author_rank: Regular Contributor
timestamp: August 04, 2025, 01:38:49 pm
content: Thanks floobyYes the coil is a difficult customer, Im surprised something isn't included within the contact body itself, perhaps that not how the regulations work...rehttps://www.se.com/uk/en/product/A9C15920/acti9-overvoltage-protection-auxiliary-iactp-220-240-v-ac/it does say "This auxiliary is an interference suppressor which limits overvoltage on the control circuit" but yet its unclear from the data sheet its exact intended use, I'll reach out to Schneider for clarification, thanks again for the reply. H

author: hazzer
author_rank: Regular Contributor
timestamp: August 06, 2025, 04:31:48 pm
content: The A9C15920 RC network arrived, its designed to clip onto the left side of the contractor and has integrated contacts to make direct contact to the coil, (the second RC is I assume for another contractor coil and not a switched load - I awaiting a reply from Schneider to confirm).On a HP 4192A it measures as a series RC of 220ohms and 210nF (give or take....) both RC's are the same values.So safe to say that my QSpice model is over simplified and does not give good values.... (someone is saying no surprises there)If I hear back from Schneider I,ll close with their reply.Thanks again for the input.Harry

author: Seekonk
author_rank: Super Contributor
timestamp: August 08, 2025, 02:17:28 pm
content: We had a batch suppressors come out of potting and they couldn't remember what parts they put in. Didn't take anything that fancy. If you're trying to figure how that happened, don't. We were ISO 9001. One day I was working on a new design (not suppressor) and they came with a box of product and complained that none of them worked. It was what I was still working on. It turned out in the procedure book that engineering didn't need to sign off on a design before it went into production. Management continued to refuse to change that before I left.

author: hazzer
author_rank: Regular Contributor
timestamp: September 13, 2025, 12:27:49 pm
content: Follow up.... for anyone reading this later....I needed space in the Consumer Unit and ended up replacing the Schneider Electric A9C15920 withhttps://www.ebay.ie/itm/406053237175its a generic RC snubber for 240Vac relays etc, and it works fine, no overshoot... and cheaperwhen installing try and get it as close as possible to the contractor coil.PS - notice the flat top on the mains sine wave, that's common now with all the SMPS in households...