high power latching relay

[carmusic]

Hi i try to find on internet for a latching relay for 100A and 100V DC resistive loads, all the ones i found are at 28V dc max
If you found something even if it is from china i would be very interested

 

[blueroomelectronics]

A Digikey search found some but they're not latching and are $230.

 

[Leftyretro]

Hi i try to find on internet for a latching relay for 100A and 100V DC resistive loads, all the ones i found are at 28V dc max
If you found something even if it is from china i would be very interested

You may have more luck looking for relays that have extra auxilary contacts and wire them in as a latching circuit. Not sure how much luck you are going to have finding 100amp DC rated contacts. Also what coil voltage are you requiring? Probably more information about what you are actually controlling and how it needs to operate (how will relay be turned on and turned off) might help us find you alternate solutions.

Lefty

 

[carmusic]

coil contact should be 24vdc or 12vdc i am controlling big transformers Rectifiers that outputs 100Vdc 100A maximum for cathodic protection
i have found a lot of 200A latching relays but always 30Vdc max

 

[blueroomelectronics]

What are you switching that has a 10,000W load like that?

 

[carmusic]

it is use to cut power for cathodic protection of pipelines

would it be possible to make this with mosfet since it is a resistive load. the reverse diode in mosfet will make troubles i think since i must have no polarity (must work in both ways and don't want the diode to conduct)

 

[user_88]

Here is a 200V DC @ 200 A DC relay:
**broken link removed**

It might be a good idea to include a safety factor on your current and voltage ratings.

As mentioned above, you would have to devise an appropriate latching scheme.
Maybe just get a smaller latching signal relay to energize the main relay coil.... shouldn't be a problem.

 

[carmusic]

thanx i had found those but they are over 300$ each!!!

 

[blueroomelectronics]

thanx i had found those but they are over 300$ each!!!

Yep, maybe you can find some used ones on eBay. A 10kW anything will not be cheap.

 

[hotwaterwizard]

Big Amps cost Big Bucks!

What is your coil voltage?

Here is a 12v Power Relay for $6.50 **broken link removed**



12 VDC POWER SOLENOID | AllElectronics.com

 

[Leftyretro]

Big Amps cost Big Bucks!

What is your coil voltage?

Here is a 12v Power Relay for $6.50 **broken link removed**



12 VDC POWER SOLENOID | AllElectronics.com

However it has a limitation: "50% duty cycle. 10 seconds on. "

It's designed to start a car engine, not for continuous operation.
Lefty

 

[user_88]

IGBTs

This page from a vendor says that their IGBTs can be used in parallel for higher current applications.

Would it be possible to arrange something that would accommodate your requirement for current in both directions?

International Rectifier - Product Information

Here is one item that appears to be adequate for 30A DC ....
**broken link removed**

If the costs are acceptable, obtain several and see if they actually do what you want.

Maybe the company will give you some samples ....

 

[user_88]

Power Switching in the Real World

There is an upcoming article about power switching using FETs and IGBTs in the January 2009 issue of Circuit Cellar Magazine.

The author says that his experience with paralleling IGBTs for higher current applications exhibits some unequal current sharing in such an application. ....with some units becoming hotter than others... and that he prefers FETs for parallel current usage.

It may be that the IGBT parts that are available at this time have improved, and would be worth a trial, or some sort of actual test before you reject their usage.... particularly if they are free samples.

There is supposed to be a follow up article in the CC magazine in February... regarding practical Power Switching cookbook circuits.

 

[carmusic]

if i do a switch with about 10 mosfet in parallel, could it work? will the current be share (i will take all similar mosfet with same rds)
can i put them back to back to make a swtich with no polarity?

if it is possible even with 20 mosfet it would be still be less expensive than a mechanical relay (minimum 200$ for a good one!)

 

[user_88]

if i do a switch with about 10 mosfet in parallel, could it work? will the current be share (i will take all similar mosfet with same rds)
can i put them back to back to make a swtich with no polarity?

if it is possible even with 20 mosfet it would be still be less expensive than a mechanical relay (minimum 200$ for a good one!)

What I was thinking was to try one bank of 5 or so, with a common gate signal, to be used for one direction of current, and a separate bank of the same number, in parallel, to be used for the opposite current direction. Then you have to think of some way to trigger each respective gate signal, when it is required. ....Not exactly sure how to do this .... maybe zero in on one or other side of the AC line polarity....

I don't think a back-to-back series arrangement would work. However, it looks like the IGBT specifications are robust enough to stand up to whatever is required .... just a matter of getting the gate signals to fire when you want them to....

... Are you thinking Mosfet or IGBT?

 

[carmusic]

well i don't have any experience with igbt but if they can work ill search some info

 

[hotwaterwizard]

SCRs will work anSCR will latch with DC and they are cheep.

 

[user_88]

The 30 A DC rated IGBT that I referenced earlier was quoted at somethng like $4 US.
I haven't sourced any Mosfets yet .....It just sounds like the IGBTs would be worth looking at .... Place 3 or 4 in parallel and measure the rated current....also check for any temperature excursions.

The one thing about SCRs is that once they are turned on, they stay on until the current goes to zero. This would work for a rectified sine wave, but not if you had any sort of filter capacitance .... a sustained DC current.

 

[Leftyretro]

SCRs will work anSCR will latch with DC and they are cheep.

Yes, but then how do you turn off the SCR once it starts to conduct DC current? He would not be able to turn the power off without either removing the load under power or cutting the source power via breaker or such.

Lefty

 

[carmusic]

thanks for all the answers, i finally found out a specialized relay that is good for 150amp at 750vdc from a china manufacturer with UL approvals