[pYr0rAGE]

Hello all

I am new to designing high power circuits, and recently ordered an EV200 contactor without an economizer. Now, after attempting to install it, I managed to blow it up. I figure it was a combination of the following factors:

1) Not having any kind of economizer circuitry in place
2) Running the coil off of 18.5V instead of 12V

Now, touching the coil terminals reads an open circuit. I figure that by running it at too high of a power, the coil drew too much power and fried itself (although, right after the incident, the case didn't feel particularly warm...)

So, here's my question to the board: I am going to try again with this relay. It is the same as the one I was using before, but it has an economizer built in. Now, in order to prevent me from blowing it up again, here are some precautions I am going to take:

1) Set up a voltage divider circuit to reduce the voltage at the + side of the coil to 12V
2) Measure the resistance of the wires through the coil and find out how much power the wires will draw at inrush. It if looks too high, reduce the voltage further.

My questions to the board are...

1) Did the relay blow up for the reason I think it did (too much power dropped across the coils)?
2) Are the steps I'm taking above necessary?
3) Is there something I'm leaving out that would cause the coil to blow up again?

Thanks for your time!

-pYr0

Why aren't you running 12 volts? Or more like 13.5 volts to power the relay coil? Why 18 volts? That is pretty high but I think they can do like 18 but that is the upper limits. Why run electronics at the upper limits? You are asking for trouble. I would not want to give it more than like 15 volts max. Do you have it fused?

Get a good DC to DC Converter and one that will output like 13.6 or 13.8 volts and just use that. I have a bunch of those and never have put more than 15 volts to them.

Pete

[pYr0rAGE]

Well, here is the thing: the module that this part is being used on runs off of an 18.5V lipo battery (which really gives off around 21V when fully charged), so there isn't really a 12V or 13V rail. (Note: sorry about being extremely vague about the application, but I can't quite tell what this part is being used in just yet)

The linked datasheet for the EV200AAANA says that a part with this code, specifically the "A" in the 2nd slot, has a coil that can handle 9-36V. If that's true, then 20V is nowhere near the upper limit. I'm honestly not sure where Digikey got the 12v from. In any case, wouldn't creating a voltage divider circuit with power resistors create a virtually identical case as with the 12v rail?

Technically, we have the coil fused, but it's connected to a 150amp circuit breaker, so effectively no. What size fuse would you recommend?


Oh, and thanks for the quick response!

[piotrsko]

some rip-offs of these are chinese and if purchased really cheap aren't worth the price. they look the same but won't handle specs.

instead of resistors, 12vdc shunt regulators come in a 3 pin TO-72 case and stack for currents.

[pYr0rAGE]

I purchased from digikey both times. Usually they don't sell rip-offs? How would I tell the difference between a rip-off and a genuine part?

I still don't quite understand why the digikey specs page rates the coil for 12V but the data sheet rates it for 36, or which one to believe.

Thanks for the quick responses, guys.
-pYr0

[frodus]

Why did the first EV200 NOT have an economizer? Are you sure it wasn't a 12V LEV200? That is the same style, but without economizer. I've never heard of an EV200 without economizer option.

The EV200 indeed does work 9-36VDC, so using it in that range is just fine, but the economizer SHOULD REMAIN CONNECTED, DO NOT REMOVE IT.

It sounds like you ordered one thing, got something else, and ran it over it's ratings. That or you ordered the wrong one and ran it over it's ratings. A real EV200 with economizer will work in your range without doing some voltage divider or some other crap.

It you did indeed get an EV200 with 9-36VDC economizer, use it with the economizer.

here's the PDF
http://relays.te.com/datasheets/ev200.pdf

Digikey should list it as 9-36VDC

[frodus]

Evfun,
The contactor uses 1.7w with the economizer. jrp said it uses 3.5A at 13.4V without. The coils need 7v to hold and 9v to pull in. Its in the datasheet.

[EVfun]

Is the coil in the units with the economizer the same as the coil in the units without the economizer? I ask because the contactor supposedly needs only 1.7 watts to hold and we know the coil resistance is 3.8 ohms. There is no way to apply 7 volts to a 3.8 ohm resistance and only consume 1.7 watts -- something isn't adding up here.

[major]

Originally Posted by EVfun

Is the coil in the units with the economizer the same as the coil in the units without the economizer? I ask because the contactor supposedly needs only 1.7 watts to hold and we know the coil resistance is 3.8 ohms. There is no way to apply 7 volts to a 3.8 ohm resistance and only consume 1.7 watts -- something isn't adding up here.

I agree but would rather use a couple extra watts and not have it unintentionally open upon hitting a bump in the road 10 watts isn't bad if the coil doesn't overheat. I have a couple of these with the economizers off. I'll stick them on the power supply tomorrow and see.

[EVfun]

If they are really only designed to dissipate a couple watts 10 watts might overheat the coil. Think about how hot a resistor gets killing 10 watts and then imagine it in a plastic box. The coil doesn't get any cooling from the traction pack cables (well it better not or isolation is compromised!)

I look forward to your test results.