Guardian Electric A410-063626-00 Relay Question - Page 1
Forum section: electronics / projects

author: ko4nrbs
author_rank: Regular Contributor
timestamp: September 17, 2022, 01:46:30 pm
content: I want to use an open frame NOS Guardian Electric A410-063626-00 relay in an old AM transmitter to control the 300vdc HV. It will permit me to move the HV off the function switch which is prone to failure and unobtainable. The relay has a 24vdc coil and the contact rating is 10 amps at 120 volts. The coil has that rating stamped on it and doesn't say of it is an AC or DC rating. I can't find a Data Sheet on this relay in order to see what DC voltage the contacts are rated for. I'm concerned about the maximum isolation DC voltage the contacts have.In operating once the relay switches in the 300vdc HV it will remain there for the duration of the transmitters operation. In other words it won't be switching the HV in and out as I transmit.Anyone familiar with the Guardian Electric relays?Thanks,Bill

author: ko4nrbs
author_rank: Regular Contributor
timestamp: September 17, 2022, 02:00:22 pm
content: Just found this Data Sheet after discovering another number on the coil. Looks like it has an AC coil so it won't work in this application.https://datasheet.octopart.com/1240-2C-120A-Guardian-Electric-datasheet-31828072.pdfBill

author: SeanB
author_rank: Super Contributor
timestamp: September 17, 2022, 02:19:17 pm
content: I would look for a relay with bigger contact separation, and which is rated for 300VDC operation on the contacts, as a 120VAC contacor contact is not rated at all for DC operation over 60VDC, they tend to arc over and not extinguish when used at 300VDC. I would suggest putting the relay contacts in the secondary winding of the transformer, before the rectifier tube, so that they run on AC and not DC, as that way the arc chutes can actually break the arc successfully, otherwise you will need HVDC relays to do it on the output side.Something like this,https://www.mouser.co.za/ProductDetail/Fujitsu/FTR-F1CA024R-GW?qs=CiayqK2gdcIZmZR1KINicg%3D%3Dwhich was just a simple search away for 300VDC rated ones, was the first result, will likely be a lot better, though they also have ones with higher DC voltage ratings.

author: ko4nrbs
author_rank: Regular Contributor
timestamp: September 17, 2022, 03:37:57 pm
content: The schematic shows the Final Amplifier DC voltage being 340 volts so I better go with a 400 volt relay. How did you find the 300 volt one?Bill

author: TimFox
author_rank: Super Contributor
timestamp: September 17, 2022, 04:04:18 pm
content: Quote from: SeanB on September 17, 2022, 02:19:17 pmAn interesting relay, with such a high voltage rating in a small package. Note that the contact voltage rating falls below 300 VDC for current above 0.3 A.

author: ko4nrbs
author_rank: Regular Contributor
timestamp: September 17, 2022, 04:34:24 pm
content: Quote from: TimFox on September 17, 2022, 04:04:18 pmThe maximum current I will be dealing with is only around 2.5ma.Bill

author: jonpaul
author_rank: Super Contributor
timestamp: September 17, 2022, 04:40:53 pm
content: Dow-Key and others make HV DC realys.Many are sealed.Alternative cheap solution: use a similar relay like the Magnecraft, with correct coil, and DPDT contacts.Wire the two poles in series with armature jumped.That creates a 2X rating and magnetic blowout.Jon

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 17, 2022, 05:08:27 pm
content: Have you considered a DC SSR?

author: ko4nrbs
author_rank: Regular Contributor
timestamp: September 17, 2022, 05:08:55 pm
content: Not yet.Bill

author: themadhippy
author_rank: Super Contributor
timestamp: September 17, 2022, 05:35:16 pm
content: QuoteQuotessr leakage current might be a problem

author: jonpaul
author_rank: Super Contributor
timestamp: September 18, 2022, 05:00:14 am
content: SSR will NOT work at 2.5 mA de to holding currtn limitation.Most SSR are AC not DCj

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 18, 2022, 05:09:42 am
content: Holding current is irrelevant for DC SSR, which is just a MOSFET plus an isolated gate driver of some sort.