Solid State Relay Death - Alternator Control

Specifications, applications, part numbers, and prices for various OEM fuel injection components.

Moderators: jsmcortina, muythaibxr

Solid State Relay Death - Alternator Control

Postby pjkinsella » Tue May 09, 2017 1:23 pm

Question about running the SSR that is spec'd in the MS3Pro manual:

I bought one to handle the current for activating the field coils in my 98 Dodge Viper alt. using "High-speed Feedback Field Control." I got it all wired up and it seemed to work pretty well for maybe an hour of use and subsequently died (I noticed immediately that it got too hot to touch). Just to be sure it was the relay that died, I plugged in a spare identical SSR and it worked again, so I'm assuming I overloaded the SSR (should be rated at 40A according to the MS manual). I can't imagine the field coils drawing such high amperage, but I don't completely understand how they work either... The only other thing I can think is that maybe the SSR can't handle the switching frequency that was being thrown at it. Thoughts on this?

I just ordered a 100A SSR, but I'm still concerned about the switching frequency being the factor instead of the amp draw.

Any tips would be really appreciated. Having an alternator that won't charge tends to be a drag. Thanks!!
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby old guy » Wed May 10, 2017 3:58 pm

Where did you get the SSR ? I have seen reports of a lot of the Chinese ones sold on E-Bay failing.
old guy
Experienced MS/Extra'er
 
Posts: 328
Joined: Thu Jan 24, 2008 9:20 am
Location: North Carolina

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Wed May 10, 2017 5:45 pm

old guy wrote:Where did you get the SSR ? I have seen reports of a lot of the Chinese ones sold on E-Bay failing.


It's a Dorman 902-303.
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby billr » Wed May 10, 2017 8:25 pm

Do you have a spec sheet for that relay? The Dorman site is down right now, and I can't find the specs elsewhere. Are you sure it is an SSR? None of the descriptions I find for it call it an SSR. If it is an SSR, is it installed in a hot environment? Many (most?) SSRs that handle 40A require mounting to a heat-sink, and get de-rated significantly as ambient temp rises.
billr
Super MS/Extra'er
 
Posts: 4462
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Thu May 11, 2017 4:36 am

billr wrote:Do you have a spec sheet for that relay? The Dorman site is down right now, and I can't find the specs elsewhere. Are you sure it is an SSR? None of the descriptions I find for it call it an SSR. If it is an SSR, is it installed in a hot environment? Many (most?) SSRs that handle 40A require mounting to a heat-sink, and get de-rated significantly as ambient temp rises.


I remember searching for it rather extensively and I ended up just trusting the information in the MS3Pro manual (attached). The Dorman part should be a direct replacement for the SMP RY330K.

And yes, it's in an engine compartment. I mounted it to a steel part that should stay relatively cool, but relatively is relative. I'm not sure just how much of a heat sink is necessary.

EDIT: Found specs for the SMP RY330: http://ecatalog.smpcorp.com/STD/#/vehic ... 330?type=s
Looks liek it's rated at 30A
Attachments
MS3Pro - SSR.jpg
MS3Pro - SSR.jpg (57.66 KiB) Viewed 245 times
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby billr » Thu May 11, 2017 8:48 pm

Still no real specs there, specifically the temp de-rating curve. Common industrial 40A SSRs de-rate to about 10A at 100C. Note that both SMP and Dorman refer to this as a "fan relay"; I wonder if it is meant to be mounted on the front (cool) side of the radiator?

Another factor may be fly-back from the alt field. That is a pretty hefty inductance as compared to a fan motor. What is the rated amp output of your alt? That may give some clue as to what to expect for the max field current.
billr
Super MS/Extra'er
 
Posts: 4462
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Solid State Relay Death - Alternator Control

Postby slow_hemi6 » Thu May 11, 2017 10:34 pm

On a true field control alternator, one without any other internal circuitry, just a set of brushes, I always just use a RE55. Those things are virtually bulletproof. Some computer controlled alternators like certain mitsubishi have internal circuitry to make them more fail safe so they will self excite and have a default regulated voltage should the computer control give up.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
User avatar
slow_hemi6
Super MS/Extra'er
 
Posts: 4120
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Fri May 12, 2017 4:38 am

billr wrote:Still no real specs there, specifically the temp de-rating curve. Common industrial 40A SSRs de-rate to about 10A at 100C. Note that both SMP and Dorman refer to this as a "fan relay"; I wonder if it is meant to be mounted on the front (cool) side of the radiator?

Another factor may be fly-back from the alt field. That is a pretty hefty inductance as compared to a fan motor. What is the rated amp output of your alt? That may give some clue as to what to expect for the max field current.


Yes, I believe in OEM applications it was mounted on the radiator. I assumed that it would be significantly below it's current rating, but I really don't know (nor do I know how to check in this situation). It should be a 143A alternator, I believe. I'd be interested to know how to estimate the field current based off of that.

I bought a Fotek SSR-100DD, but now I'm wondering if it's one of the counterfeit ones. I'm also concerned that its response time won't be fast enough for PWM.

slow_hemi6 wrote:On a true field control alternator, one without any other internal circuitry, just a set of brushes, I always just use a RE55. Those things are virtually bulletproof. Some computer controlled alternators like certain mitsubishi have internal circuitry to make them more fail safe so they will self excite and have a default regulated voltage should the computer control give up.


I don't believe this alternator has any internal circuitry like that. It does a whole lotta nothing when the field wires are disconnected. This may be the route I end up taking.
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby billr » Fri May 12, 2017 11:21 am

What is the resistance of the field coil? That won't tell the whole story, as it will change as temp rises and turn on/off spikes are sure to be there; but it will give some idea. You could try measuring the DC current, but I would be wary of just using the typical multimeter with a 10A unfused circuit for that. My perception is that my 60A alt has a field current of 4-5A, so that 143A unit may be over 10A.
billr
Super MS/Extra'er
 
Posts: 4462
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Sat May 20, 2017 6:20 am

billr wrote:What is the resistance of the field coil? That won't tell the whole story, as it will change as temp rises and turn on/off spikes are sure to be there; but it will give some idea. You could try measuring the DC current, but I would be wary of just using the typical multimeter with a 10A unfused circuit for that. My perception is that my 60A alt has a field current of 4-5A, so that 143A unit may be over 10A.


I STILL haven't had a chance to re-check this (also working on a much bigger problem with ignition), but I remember with the car not running, the resistance read quite high. High enough that I didn't trust the reading and decided that it wasn't a good indicator when the engine isn't running. And I agree, I'm wary of testing the amperage with my multimeter.

So, even if it's drawing, say, 15A, wouldn't that be a non-issue with a 30A capable SSR? Do you think the high speed switching might be a part of the problem? I'm using one of the PWM outputs on the MS3Pro - not sure if there's a setting for that output that might make a difference.

I swapped the dead SSR for a new identical one and put it on a large aluminum heat sink and it seemed to work for an even shorter period of time (like, minutes).

This issue is going to be my next big problem keeping my car in the garage once I finally get my ignition sorted.
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby billr » Sat May 20, 2017 10:12 am

Sure, switching speed could be a factor. Most heating will be during the off/on/off transitions. The more transitions there are during a given time period, the more the SSR will heat up. Remember, most of these commercial SSRs are designed (and rated for) slow on/off control, not PWM. Try to get a good reading on the field coil resistance, even if you have to open the alt up a bit to measure right at the slip rings. Without any clue as to the current draw, we are just wandering in the weeds here...
billr
Super MS/Extra'er
 
Posts: 4462
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Solid State Relay Death - Alternator Control

Postby jsmcortina » Sat May 20, 2017 11:22 am

The high-speed PWM could easily kill it if the SSR isn't designed for it. Make sure you add a flyback diode in the wiring.
http://www.msextra.com/doc/pdf/html/MS3XV30_Hardware-1.4.pdf/MS3XV30_Hardware-1.4-54.html
Although I specified a 1N4001, you could use a higher current diode such as a FR302.

James
I can supply, repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: viewtopic.php?f=104&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
jsmcortina
Site Admin
 
Posts: 33394
Joined: Mon May 03, 2004 1:34 am
Location: Birmingham, UK

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Sat May 20, 2017 11:31 am

jsmcortina wrote:The high-speed PWM could easily kill it if the SSR isn't designed for it. Make sure you add a flyback diode in the wiring.
http://www.msextra.com/doc/pdf/html/MS3XV30_Hardware-1.4.pdf/MS3XV30_Hardware-1.4-54.html
Although I specified a 1N4001, you could use a higher current diode such as a FR302.

James


Thanks James. I do not have a flyback diode. Maybe that's my issue??
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY

Re: Solid State Relay Death - Alternator Control

Postby pjkinsella » Mon Jun 12, 2017 8:34 am

I believe I've solved my problem by adding a flyback diode! Thanks for all the help guys!
Current Project: 1998 Dodge Viper GTS
pjkinsella
MS/Extra Newbie
 
Posts: 18
Joined: Wed Apr 26, 2017 4:33 am
Location: Louisville, KY


Return to OEM EFI Hardware

Who is online

Users browsing this forum: No registered users and 1 guest