Obsolete SES C230E SCR Thyristor Replacement - Page 1
Forum section: electronics / repair

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 19, 2014, 03:30:45 pm
content: Hi,I've been handed a very old motor speed controller to repair. I've narrowed it down to this thyristor but it's obsolete,SES C230E Datasheet:http://www.alldatasheet.com/datasheet-pdf/pdf/579002/DIGITRON/C230E.htmlI'm looking for a suitable alternative available from stock from Farnell/RS/Mouser/Digikey but I'm not all that familiar with SCR specification.So far the parameters I'm searching by arePeak repetitive off state voltage >= 500vPeak non-repetitive reverse volatge >= 600vForward current RMS >= 25APeak Surge Current >= 250AForward "on" voltage <= 1.9vGate Trigger Current < 25mAGate Trigger Voltage <1.5VHolding Current <50MATurn On Time ~1uSTurn Off Time ~23-35uSI found this one, its a little physically larger (I have room) and the Forward Current is 63A, but I figure the bigger the better there right?http://docs-europe.electrocomponents.com/webdocs/0a35/0900766b80a35a6a.pdfThe only thing is that it has a holding current of 100mA, I'm not sure if that matters or not.If I stick to the 50mA max holding current I can't find anything in a stud mount format, that doesn't bother me as there's a large heatsink to mount to anyway. The best I can find ishttp://www.mouser.com/ds/2/240/Littelfuse_Thyristor_Sxx35x-63752.pdfSo can anyone tell me if I'm on the right lines and what are the key specifications to look out for when replacing obsolete SCRs?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 19, 2014, 03:57:52 pm
content: Turn off time (t_q) is much shorter on the original part, it's probably an "inverter grade" device, or something near that. Well.. maybe not that much. It's not guaranteed, nor is critical dV/dt.That S6035 is probably a good idea. It's even available (well, they make it in... not that you'll necessarily find it in stock at a distributor) in wire lug format.Tim

author: SeanB
author_rank: Super Contributor
timestamp: November 19, 2014, 04:08:55 pm
content: Gate voltage and gate current are more important. The one you want to buy will need a little more current, but as you are using a transformer to drive it it probably has a low enough output impedance to trigger it. Only way is to try, or use a TO220 device with a current rating of around the same level. With lower current the gate drive should reduce though, so it likely will work.Why do you think it is the SCR, they typically fail as short or open, or with a gate current that needs to be in the amp range to turn it on.

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 19, 2014, 04:21:13 pm
content: Thanks guys, I'm getting a dead short between Anode and Gate on the old one. I'm doing some cold tests on the rest of the circuit to see if it was anything in the driver side that caused it.The motor etc. is apparently all fine (according to the site technician)The drive works off a tacho so I can't test here except the old "turn on and hope for no smoke".

author: wraper
author_rank: Unknown
timestamp: November 19, 2014, 04:25:59 pm
content: First variant ixys scr is a no go as it have 10 times higher max gate trigger current, second choice is closer but have 4 times higher Igt too, so unless you use exemplar with much lower Igt than maximum allowed, it is much better to find another replacement.

author: SeanB
author_rank: Super Contributor
timestamp: November 19, 2014, 04:32:58 pm
content: True, but most devices are a little more sensitive than the spec, and most drivers use a higher current to drive them, unless you are limited in power. Pulse drive will typically use a high current to do it, so likely here it will work, as the currents are within the spread of values, and the drive transformer likely does give enough current to the gate.

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 19, 2014, 04:51:39 pm
content: The lowest Igt I could find was the CS19-08ho1, but it's only 28mA which isn't all that different.So if I'm understanding correctly too high a value of "Igt" means the thyristor will fire later in the cycle given the same drive circuitry?

author: wraper
author_rank: Unknown
timestamp: November 19, 2014, 05:11:58 pm
content: Quote from: bookaboo on November 19, 2014, 04:51:39 pmIt depends on control circuity. If current is enough from the beginning it will simply fire. If there is some current ramp and not enough from the beginning, then it could fire with a delay. If there is not enough current, it will stay closed.

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 19, 2014, 05:14:30 pm
content: Thanks to all, I'm going to try a S6035 in as a replacement and see what happens.

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 27, 2014, 04:15:33 pm
content: Just a quick update, just spoke to the service engineer who informs me that repair has been working perfectly with the S6035 as a replacement. Many thanks again to all.