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SX460 Voltage Regulator for Old Onan Generators


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  #1  
Old 11-05-2014, 08:54:41 PM
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Jim McIntyre Jim McIntyre is offline
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Default SX460 Voltage Regulator for Old Onan Generators

First off, I'm no expert in this area. But I have spent some time troubleshooting, replacing, designing and building voltage regulators for gensets. A few years back I became aware of a very common voltage regulator for generators that was referred to as an SX460.

A quick search on eBay shows up many of these. They are even available on Amazon. Here's what they look like:



Near as I can tell, the SX460 was a regulator designed 'back in the day' by Newage Stamford. I think Cummins may have bought Newage. Anyway, the manual for the SX460 shows up on Cummins site:

https://www.cumminsgeneratortechnolo...specification/

I've never checked to see what Cummins charges for an SX460, but I'd guess it's a touch more than $29.99. Clearly, the eBay SX460 is a Chinese knock-off. Hopefully a 'clone'. But honestly, I have no idea.

So that brings up the first issue. If you're not willing to tinker around with a no-name $29.99 piece of electronics, read no further. These things are cheap, and maybe for a reason. If you have no sense of adventure, despise Chinese knock-offs, or need a reliable genset for your grandmother's heart-lung machine, just move on...

That said, there's no good reason a decent $30 voltage regulator shouldn't be available. These things aren't complex, full of expensive parts, or require years of development to design.

So, I bought one...

And I put it in my Onan 7.5 DKD. It's working fine.

The specs for the SX460 have a couple of things to watch out for.
  1. First off, the SX460 is designed for brushless sets. (If you want to try it in something with brushes, think twice. It might be OK, but I do see some issues). So assuming you have a brushless set, like a DKD, DJE, JC, etc, these ought to work. They're rated for 4A of field drive current, so they ought to be good for larger sets, too.
  2. Next, the SX460 specs call for a 15 ohm minimum field resistance. You need to know what your field resistance is. Then, if it is less than 15 ohms, add in some series resistors to get a 15 ohm total. My DKD needed 8 ohms added to get this.
  3. Finally, remember this thing is going to fail someday. Maybe soon, maybe later. But when it does fail, it'd be nice if it didn't take your generator and AC loads with it. This is the tricky part. Onan, in their original design for the YD-based 'J' sets included a field circuit breaker, probably recognizing the same issue with their electronic regulator. So, figure out how much field current you need, and add in a fuse.

Last edited by Jim McIntyre; 11-05-2014 at 09:25:51 PM.
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Old 11-05-2014, 09:21:11 PM
Max Thompson Max Thompson is offline
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Default Re: SX460 Voltage Regulator for Old Onan Generators

This sounds like something I would like to play with someday. It would sure beat $130 for a VR board in the JCs.
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Old 11-05-2014, 09:32:40 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Cummins did buy Newage. Sold them for quite a bit more than 30.00 dollars.
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Old 11-05-2014, 10:18:39 PM
Isaac-1 Isaac-1 is offline
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Default Re: SX460 Voltage Regulator for Old Onan Generators

The Chinese clone SX-460's seem to come in a few quality grades, or at least variaitons, some have labels with terminal markings, some don't, some use better quality premade jumpers) I have used a couple on MEP-016 series 3KW generators, so far with fairly good luck (one defective unit that fried right away). I have not bought one in a couple of years but at that time they were selling for around $70-$90 shipping from the U.S. or $40 with a 30 day non express shipping from China. It is strange replacing a shoe box size AVR with something the size of a pack of playing card, but they do seem to work.
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Old 11-05-2014, 11:38:57 PM
len k len k is offline
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Default Re: SX460 Voltage Regulator for Old Onan Generators

For my own gen think I'ld prefer to rebuild my reg than buy China, at least for my primary gen that supplys my heating furnace.

In the middle that TO-220 transistor on a heat sink is likely the main power transistor (hot). If it feels too hot put a fan on it or move it in to a flow of cooling air

Many times in electronics it's the hot running power semiconductors that die. Many companies don't pay enough attention when designing to keeping them cool and derate power dissipation for hot heat sinks. Biggest thing for reliability is if the power transistors run hot you need to put a fan or bigger heat sink on them, MUST keep the die junction temp below ~ 180 deg F MAX. (max limit on case temp is a lower temp, thermal resistance of package)

On size I notice the JC type regs are designed the old fashion way , with lots of space and big bulky components. My NHM reg uses a lot of surface mount components in the logic stuff, they don't run hot. That's likely how they shrink it down in size, and maintain reliability.

Last edited by len k; 11-06-2014 at 12:07:11 AM.
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Old 11-06-2014, 12:06:56 AM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

The best way to keep parts cool is to not dissipate power if you don't have to. I'd guess the SX460, like the Onan YD regulator, uses SCRs, not transistors. So the dissipation boils down to 4A (at MAX) across a couple of forward-biased silicon junctions. Under 6 Watts. If the SX460 uses MOSFETs, the dissipation is probably even less. It is not a linear regulator.

My JB and DKD only need about 1 amp of field excitation. The SX460 doesn't even get warm to the touch.

I'd be inclined to repair a broken Onan regulator too, except that the only one that I've had fail was one of the 'marine' style ones, and completely potted. Definitely NOT worth the bother.
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Old 11-06-2014, 12:15:09 AM
len k len k is offline
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Default Re: SX460 Voltage Regulator for Old Onan Generators

My Onan reg (NHM) had aluminum case, I drilled a hole in back and added 150 psi air. Case was mildly corroded so potting didn't stick, and whole potting block popped out in one piece. But yes picking potting is a pain even with my clear potting. Guess that's why it's still sitting in a box waiting for me to finish it. But $8 for IGBT vs ~ $250 for reg is an incentive.

Really what I want to do is get it running and see how hot the IBGT gets and modify heat sink if I have to. My field is 3 amps max, TO-220 package replacement IGBT dissipates ~ 7 watts, free wheeling diode is next to it , maybe 2 more watts there (PPM). Big gap in contact between bar IGBT is on and larger Al case, big burr on drill hole

Last edited by len k; 11-06-2014 at 01:11:38 AM.
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Old 11-06-2014, 08:15:48 AM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Flight Systems sells their version, with a substantially more robust heat sink, for $159. FYI... The CPG genuine SX460= $434. All the Newage bits and pieces are a little spendy-- just the nature of the business.

All OEMs will charge premium for their "original" parts. That's what make NAPA et al successful.
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Old 12-10-2014, 07:43:26 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

So If I was going to use one of the SX460 VRs on a DJC which has a field resistance of around 12 ohms I should use a 4 ohm resistor in series with the field. What wattage rating would be needed to be safe. I believe the field current is in the 1A range so am thinking a 15-20W resistor would be appropriate. It would seem to make sense to run it through the original field breaker as it is handy and should be close to the correct size? Cheers Dan
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Old 12-10-2014, 08:40:25 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Yep - your approach looks good to me...

15 ohms, being the minimum, you might want to go a touch higher...

I got mine at Mouser.
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Old 12-10-2014, 09:21:25 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Think those types want to be mounted to a heat sink, with that white thermal grease in between.
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Old 12-10-2014, 09:53:54 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Yep - they ought to be mounted to a metal something. I just bolted mine to the inside of the steel control box. You can skip the heatsink grease for this - it helps, but isn't needed for stuff like this...
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Old 12-10-2014, 10:35:43 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

I've used these before, I'ld use the thermal grease. A 25watt resistor without a heat sink is the same size as a ~2 watt carbon resistor. That implies they are heavily relying on heat sink to cool the package. The grease fills the gaps between the surfaces, even in a highly flat surface of a CPU sink there are a lot of micro air gaps.
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Old 12-10-2014, 10:48:12 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

It doesn't matter that it's a 25W resistor. In this application, it is dissipating 8 Watts or less. If the OP has H/S grease use it, but don't sweat it if not.
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Old 12-10-2014, 11:02:31 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

So on your DKD, you just put the SX460 in connected to the 240v output, and then the excitor connected to the output of the SX460? The current transformer in my DKD is in series with the output, but it obviously doesn't have to be wired that way.

Thanks,
Tad
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Old 12-10-2014, 11:36:59 PM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

The other thing I was uncertain about was where to hook up the ac sensing connections, the wiring diagrams I have seen indicate that it is hooked to the main windings. I believe that the JC has a separate winding which supplies the field only? Any thoughts?
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Old 12-11-2014, 12:04:28 AM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Quote:
Originally Posted by bigblockchev View Post
The other thing I was uncertain about was where to hook up the ac sensing connections, the wiring diagrams I have seen indicate that it is hooked to the main windings. I believe that the JC has a separate winding which supplies the field only? Any thoughts?
The SX460 can sense across 240V or 120V. The stock YD regulator is wired to sense 120V. It senses one of the 120V windings - I forget which one. Onan's wiring diagrams make it look as if there's a dedicated sense winding for the YD regulator, but there isn't.

Quote:
Originally Posted by Nazrat View Post
So on your DKD, you just put the SX460 in connected to the 240v output, and then the excitor connected to the output of the SX460? The current transformer in my DKD is in series with the output, but it obviously doesn't have to be wired that way.

Thanks,
Tad
I don't remember how I wired mine. As I just mentioned, the SX460 will work either way (120 or 240). The transformer in the DKD isn't used if you install an SX460.
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Old 12-11-2014, 12:08:21 AM
Jack Hottel Jack Hottel is offline
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Default Re: SX460 Voltage Regulator for Old Onan Generators

The JC 12 lead YD genend has the input leads to the regulator labeled 1 and 2. 1 connects to T1 and 2 connects to T4 internal to the stator.
Jack Hottel
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Old 12-11-2014, 10:18:49 AM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Jim, what issues are you thinking of on a brushed unit??
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Old 12-11-2014, 11:22:13 AM
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Default Re: SX460 Voltage Regulator for Old Onan Generators

Sets with brushes typically need more field current. Maybe way more than the 4A this thing is rated for. Also, they generate more noise, so adding some sort of transient protection would be a good idea, to protect the regulator...
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