# Need Help with Contactor Choose for Inverter Input Interrupt



## twoorone (Nov 13, 2021)

Hi everyone. I need an advice!

I need to cut and shut input of the inverter with a contactor because of it's freezing and not responding. Inverter has two inputs with 48v dc and 220v ac. I need to contact both by using one contactor. Dropped the inverter's sticker below. If you guys help which contactor with an Amper value I need to use , I'll be pleased.


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## backstay (Feb 3, 2011)

Where are you located? It’s from Germany and 50 Hz. Giving you American parts won’t help you.


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## twoorone (Nov 13, 2021)

backstay said:


> Where are you located? It’s from Germany and 50 Hz. Giving you American parts won’t help you.


Is there any difference about Amper value? Just need how much Amper I can use in the contactor. Grid voltage is 220V 50Hz in here but like I said there are 48V DC and 220v Ac entry to inverter.


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## backstay (Feb 3, 2011)

On the DC circuit, you need 117 amp rating to match the inverter. What do you really have coming in?


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## splatz (May 23, 2015)

I might not follow your question but I think what you asking for is a double pole double throw contactor, with contacts rated for 117 amps at 48VDC, and 22 amps at 240VAC. 

I would think you could also use two contactors, one for AC and one for DC, with suitable ratings, and the coils in parallel so they both operate at the same time.


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## twoorone (Nov 13, 2021)

splatz said:


> I might not follow your question but I think what you asking for is a double pole double throw contactor, with contacts rated for 117 amps at 48VDC, and 22 amps at 240VAC.
> 
> I would think you could also use two contactors, one for AC and one for DC, with suitable ratings, and the coils in parallel so they both operate at the same time.


I thought of that but there is a budget issue. I want to control it with wifi. If happens any contact trouble (in wifi switch) I need to by-pass the current with another two contactors for uninterrupted system. So if I would do this with two contactor, I need another two for by-pass the system. Price of four contactors out of my league. Thank you for answering.


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## twoorone (Nov 13, 2021)

backstay said:


> On the DC circuit, you need 117 amp rating to match the inverter. What do you really have coming in?


I need to wifi switching for inverter. I thought that I need 117A rating contactor as well but it came too much at the first blush for inverter. Thank you for answering.


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## Wirenuting (Sep 12, 2010)

twoorone said:


> I thought of that but there is a budget issue. I want to control it with wifi. If happens any contact trouble (in wifi switch) I need to by-pass the current with another two contactors for uninterrupted system. So if I would do this with two contactor, I need another two for by-pass the system. Price of four contactors out of my league. Thank you for answering.


What did your electrician say?


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## twoorone (Nov 13, 2021)

Wirenuting said:


> What did your electrician say?


I'm a just graduated engineer and I've got a job. I said boss we need a 117A rated contactor but he finds its price too much. My boss's profession is management. Not even engineering. So I needed a new perspective if anyone tells me a better solution.


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## Almost Retired (Sep 14, 2021)

You need _a *local*_ *experienced* Industrial electrician. Probably some networking with LOCAL engineers as well.


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## CAUSA (Apr 3, 2013)

twoorone said:


> Hi everyone. I need an advice!
> 
> I need to cut and shut input of the inverter with a contactor because of it's freezing and not responding. Inverter has two inputs with 48v dc and 220v ac. I need to contact both by using one contactor. Dropped the inverter's sticker below. If you guys help which contactor with an Amper value I need to use , I'll be pleased.
> 
> View attachment 159660


Would it not be more cost efficient to solve the reason your inverter is locking up control wise and not functioning as designed.??
Adding a contactor to bandaid the problem will just shorten the life of the equipment

Switching DC and AC in one contactor and cheaping out on the cost will leave you with a failure waiting to happen.

The contacts in a DC system needs to be very robust. And what about cycle time how often does this happen??

solve the main problem first, and save time and money.


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## twoorone (Nov 13, 2021)

Almost Retired said:


> You need _a *local*_ *experienced* Industrial electrician. Probably some networking with LOCAL engineers as well.





CAUSA said:


> Would it not be more cost efficient to solve the reason your inverter is locking up control wise and not functioning as designed.??
> Adding a contactor to bandaid the problem will just shorten the life of the equipment
> 
> Switching DC and AC in one contactor and cheaping out on the cost will leave you with a failure waiting to happen.
> ...


It doesn't so often and when a problem accurs we need to solve it remotely because of inverter setup is in a station that away from us. Station needs to work %99.99 electricity effiency. Until we go for solving the problem it'll be so long. Of course solving the main problem is cheaper than to other. But we're unable to solve the main problem so far. What kind of problem waiting for us if we contact dc and ac current with a one contactor?


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## CAUSA (Apr 3, 2013)

twoorone said:


> It doesn't so often and when a problem accurs we need to solve it remotely because of inverter setup is in a station that away from us. Station needs to work %99.99 electricity effiency. Until we go for solving the problem it'll be so long. Of course solving the main problem is cheaper than to other. But we're unable to solve the main problem so far. What kind of problem waiting for us if we contact dc and ac current with a one contactor?


Running DC and AC through the same contactor. See examples:

cheap contactor rated only for the current of AC- DC contacts fusing or not making contact over a period of cycle times.

Using a high quality contactor rated for the right DC current and factoring arching wear.- : Should give you good years of service.

So cost, is the problem. The inverter locking up will still be a thorn in your side. The bandaid solution will eventually come to a end of functioning. So the question is.

What solution can you live with. Any way it is going to cost $.


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## twoorone (Nov 13, 2021)

CAUSA said:


> Running DC and AC through the same contactor. See examples:
> 
> cheap contactor rated only for the current of AC- DC contacts fusing or not making contact over a period of cycle times.
> 
> ...


Thank you so much. I was worried about if there any chance I'm wrong with choosing contactor rate. 117A current value came to me too much at first for an inverter. Thank you again.


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## paulengr (Oct 8, 2017)

A 117 A DC contactor will be both rare and expensive. AC passes through zero every 10 milliseconds at 50 Hz. DC never does. So with AC the arc naturally quenches. With DC you have to physically break the arc which requires a much bigger device. Hence trying to find a single device to do both duties is asking for the impossible and finding an inexpensive DC contactor simply isn’t going to happen. Very few DC contactor companies still even exist because demand has plummeted as we moved away from DC motor technology. One manufacturer whose name escapes me still exists in Italy. The other one is in I think Ohio in the US.


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## backstay (Feb 3, 2011)

paulengr said:


> A 117 A DC contactor will be both rare and expensive. AC passes through zero every 10 milliseconds at 50 Hz. DC never does. So with AC the arc naturally quenches. With DC you have to physically break the arc which requires a much bigger device. Hence trying to find a single device to do both duties is asking for the impossible and finding an inexpensive DC contactor simply isn’t going to happen. Very few DC contactor companies still even exist because demand has plummeted as we moved away from DC motor technology. One manufacturer whose name escapes me still exists in Italy. The other one is in I think Ohio in the US.


We through away a bunch of DC contactors when upgrading to modern solid state DC drives in the paper mill. Some had to be 200 HP rated. You could light a cigarette off the arc when they were jogging the machine. All the electrical was mounted on, what we called “midacar” all open wiring. Not a barrier or guard to be found.


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## paulengr (Oct 8, 2017)

backstay said:


> We through away a bunch of DC contactors when upgrading to modern solid state DC drives in the paper mill. Some had to be 200 HP rated. You could light a cigarette off the arc when they were jogging the machine. All the electrical was mounted on, what we called “midacar” all open wiring. Not a barrier or guard to be found.


Most DC equipment is fairly "open" natured. Drives tend to be somewhat "DIY" in nature where there are lots of external parts to add. Safety wise things are very different. Despite what the idiots on the NFPA 70E committees may think, DC does NOT cause fibrillation at all. In fact Dalziel picked limits based on a pain threshold. Arcs don't self extinguish but arc flash is very mild relatively speaking, never mind the fact that DC equipment is almost inherently current limited much below typical AC equipment short circuit ratings. And if you've ever seen a flashover in a motor or generator or experienced it up close, you'd understand why in the DC world things tend to be so very laid back. The only major difference that is a bigger problem is that it is difficult to impossible to let go if DC gets hold of you.


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## backstay (Feb 3, 2011)

paulengr said:


> Most DC equipment is fairly "open" natured. Drives tend to be somewhat "DIY" in nature where there are lots of external parts to add. Safety wise things are very different. Despite what the idiots on the NFPA 70E committees may think, DC does NOT cause fibrillation at all. In fact Dalziel picked limits based on a pain threshold. Arcs don't self extinguish but arc flash is very mild relatively speaking, never mind the fact that DC equipment is almost inherently current limited much below typical AC equipment short circuit ratings. And if you've ever seen a flashover in a motor or generator or experienced it up close, you'd understand why in the DC world things tend to be so very laid back. The only major difference that is a bigger problem is that it is difficult to impossible to let go if DC gets hold of you.


Field brushes on the turbine generators were regularly replaced on the fly.


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## 460 Delta (May 9, 2018)

paulengr said:


> A 117 A DC contactor will be both rare and expensive. AC passes through zero every 10 milliseconds at 50 Hz. DC never does. So with AC the arc naturally quenches. With DC you have to physically break the arc which requires a much bigger device. Hence trying to find a single device to do both duties is asking for the impossible and finding an inexpensive DC contactor simply isn’t going to happen. Very few DC contactor companies still even exist because demand has plummeted as we moved away from DC motor technology. One manufacturer whose name escapes me still exists in Italy. The other one is in I think Ohio in the US.


Are you thinking of EC&M?


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## Chincia (Jan 3, 2015)

A contractor decided to save money on his installation of a large solar site for us. He used an AC disconnect switch in the solar DC input circuit. First time we opened it, it fried. The arc would not extinguish. We had to cut the incoming conductors to stop it since it was around noon & we couldn't turn off the sun.


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## JRaef (Mar 23, 2009)

twoorone said:


> I'm a just graduated engineer and I've got a job. I said boss we need a 117A rated contactor but he finds its price too much. My boss's profession is management. Not even engineering. So I needed a new perspective if anyone tells me a better solution.


The price is the price! You cannot "decide" that a smaller cheaper contactor will work.

Switching DC is much more difficult for a contactor than switching AC. 110A at 48VDC is going to require a large, expensive contactor, there is no getting around that. SOME AC contactors will also have a rating for switching DC, but it is often 5-6 time LESS than the AC contact rating. So to put that in perspective, if you want to switch 110A at DC, it might take an AC contactor that is rated 500-600A AC! You can buy a DC rated contactor, they are designed differently, but they are NOT inexpensive.

I'm still not totally clear on your goal here. You want to use a WiFi signal to isolate both the incoming AC from the utility and the DC from the solar array coming into your inverter? Why?


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## sayedmhussein (11 mo ago)

The best thing to do is to solve the issue which cause the drive to freeze, then is it possible to use a spare drive input (if available) to reset the fault using a simple cheap relay instead of shutting down the drive?

Otherwise you can try to disconnect the power supply of the logic PCB of the drive and make sure that you'll block the IGBT logic inputs as well.


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## paulengr (Oct 8, 2017)

460 Delta said:


> Are you thinking of EC&M?


No. I think it’s Hubbell or somebody similar on the American side.


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## backstay (Feb 3, 2011)

Actually, the AC input is 35 amps at 230 volts.


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## 460 Delta (May 9, 2018)

Hubbell owns EC&M



paulengr said:


> No. I think it’s Hubbell or somebody similar on the American side.


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## paulengr (Oct 8, 2017)

460 Delta said:


> Hubbell owns EC&M


That’s the one.



https://hubbellcdn.com/catalogfull/ECM_DCContactorsCatalog.pdf



Granted the catalog prices are list prices that nobody pays but AC contactors are roughly $1/A street price. So a 25 A contactor is $25. The 25 A DC contactor is $810 lust. Even at half the price it is MUCH more expensive, The Italian vendor is cheaper but only smaller sizes and still vastly more than AC.

Plus check out the dimensions. The contactors are enormous.


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## 460 Delta (May 9, 2018)

paulengr said:


> That’s the one.
> 
> 
> 
> ...


The EC&M stuff now, looks exactly the same as stuff I saw in the 80’s building a crushing plant out of used equipment from the 40’s. Why try to reinvent the wheel on low volume equipment like a DC contactor anyway?


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