# [EVDL] MPJA 40a 400vdc solid state relay



## EVDL List (Jul 27, 2007)

A couple months ago, Marlin P. Jones <www.mpja.com> had a great price 
for a 400vdc 40amp solid state relay (item# 17289RL, $16.95). I bought a 
couple to test.

Synopsis: These things are crap. Caveat emptor!

Top markings:
Gold DC SSR, model SDP4040D, CE
12-480VDC 40a load
3.5-32VDC input
Side markings (exactly as written):
Attentation CE ETS Germany, EMC tested, ISO-9001 Quality passed
AFTER TESTING, IT'S ELIGIBLE
Use spacial fuse to pretect load shorting
The temperture of sink at use must low than 75c
It's better to attend varistor for inductance load
Made in China, Gold Control Tech. Co. Ltd
Tel&Fax: 0086-5160178 2007.07.03

It had a 2.8v drop at 40 amps, and even on a huge heatsink quickly 
overheated and failed. I disassembled it to see why.

Prying off the black plastic cover reveals a badly potted PC board with 
a little toroid transformer held on with double-stick tape. The black 
potting compound was rock hard, and could not be removed by melting. I 
found that soaking it overnight in acetone did soften it a bit; if then 
heated to 200 deg.F it could be laboriously dug out. There are huge 
voids in the potting; perhaps 50% of the case actually got filled.

The PC board is single-sided, no silkscreen or solder mask, and hand 
soldered. There are no ICs, no optocoupler, it's all thru-hole parts. 
Traces that carry high current are only 0.1" wide, but have a piece of 
#18 bare wire soldered along them.

The power transistor is a Toshiba GT60M104 IGBT, rated 900vces peak, 60a 
at 25 deg.C, Vce(on)=2.4v typical, 3.7v max. The relay failed because 
they cut the leads off the transistor close to the case, and soldered 
pieces of #18 wire between the transistor lead and PC board traces; the 
solder melted on these connections due to the heat at 40a.

The base of the relay is an 1/8" thick aluminum plate. In the center is 
a 1" square x 0.020" thick white ceramic plate, metallized on both 
sides. They apparently tinned one side with solder, heated the aluminum 
plate above the melting point of the solder, and pressed it in place. 
The solder didn't stick to the aluminum, but at least it formed a weak 
bond and filled the gaps with a good heat conductor.

They then laid the 4-sided plastic case on the base, and glued it on 
with clear silicone rubber. The transistor was glued to the metalized 
surface of the ceramic plate with what looks like white silicone rubber 
(thick and rubbery; not like heatsink compound at all). It looked like a 
very poor heat transfer method, and probably contributed to the 
transistor's overheating and solder joint failures.

I haven't dug off all the black potting compound yet, so I can't trace 
out the whole circuit. But basically, it looks like a 1-transistor 
oscillator that drove the primary of the little toroid transformer, and 
a rectifier on the secondary side to drive the gate of the IGBT.
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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## EVDL List (Jul 27, 2007)

> Date: Fri, 8 Feb 2008 13:10:17 -0600> From: [email protected]> To: [email protected]> Subject: [EVDL] MPJA 40a 400vdc solid state relay> > A couple months ago, Marlin P. Jones <www.mpja.com> had a great price > for a 400vdc 40amp solid state relay (item# 17289RL, $16.95). I bought a > couple to test.> > Synopsis: These things are crap. Caveat emptor!

Hey, I bought a couple of those as well. I wanted to try one as my heater relay. I was hoping to replace the large open frame relay I am now using. My heater is drawing about 25 amps on a nominal 80 volt pack. Maybe I'll wire it in and turn the heater on to see how long it lasts 

damon
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## EVDL List (Jul 27, 2007)

Any photos of a good one and a damaged one?

: )




> Lee Hart wrote:
> 
> > A couple months ago, Marlin P. Jones <www.mpja.com> had a great price
> > for a 400vdc 40amp solid state relay (item# 17289RL, $16.95). I
> ...


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## EVDL List (Jul 27, 2007)

> [email protected] wrote:
> > Any photos of a good one and a damaged one?
> 
> I can take some with a camera, but don't have a digital one or a way to
> ...


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