TE Connectivity contactor getting stuck?

[justinjja]

I've noticed that my "LEV200A4ANA" will get suck closed/on after a while.
A few times when I tried to manually turn it off after about a month of being on it won't turn off.
I can get it unstuck by turning it on and off several times, but that defeats the purpose of it.

Is it a known thing that these devices need to be cycled from time to time?
It was sold as new (but from eBay) and looked brand new.

battery is 16s LifePo4,
Runs my whole house so fairly high currents.

 

[BentleyJ]

Its possible the contacts have been damaged and are partially welded or there has been material transfer between contacts from an arc. Since these are sealed units there is no way to visually inspect. As you pointed out, if it will not reliably open when de-energized its useless and needs to be replaced.
BTW, that model of contactor is relatively efficient as far as the parasitic load but it still adds up when energized 24/7. I replaced my energy pig golf cart contactor with 0 stand by current magnetic latching contactor and PCB control board. If you are interested, I would be happy to share.

 

[400bird]

That sounds like the contactor is welding when stuck closed. Then when you break the tacks and it opens, the contact surfaces are poor because of the broken tacks and arcing.

Are you precharging your inverter before closing the contactor? The inrush current to charge the inverter capacitors has damaged many contactors.

What's the actual peak and continuous current on your system?
The data sheet calls out 500 amps continuous, but only with giant cables (to pull heat out of the contactor)

From the data sheet, emphasis mine:
Continuous (Carry) Current,
Typical — 500 A @ 65°C, 400 mcm conductors

If this is for your home, why run a contactor? A shunt trip breaker uses no energy to stay closed. A contactor is better suited for a system that needs to turn on and off frequently (like and EV)

 

[justinjja]

No precharging but it's a high frequency inverter (Pair of growatt 5000ES)
At full load after inverter efficiencies I'm going to be under 250A.

I don't think contact welding makes sense because once I break it free it will happily connect/disconnect the load.
Only after sitting for a month does it get stuck.

I liked the idea of a contactor because in theory it was "fail open" vs the shunt trip requiring my bms to be functional to work.
Leaning towards going back to a shunt trip after this.

 

[Pyrofx]

Welded. Been there done that.
Get new ones and precharge.
Make sure you go through reputable source. There's a lot of chin6fakes out there.

 

[400bird]

No precharging but it's a high frequency inverter (Pair of growatt 5000ES)

Even high frequency inverters have capacitors. You might be putting 2000 amps through that contactor when closing without precharge.

I had an 800 watt DCDC would spike to 600 amps without a precharge. I'm sure even a HF inverter at 6500 watts will have a substantial spike across that contactor as it's closing.

At full load after inverter efficiencies I'm going to be under 250A.

My math comes closer to 300 for two 6,500 watt inverters, but you're still within the rating for the contactor.

I don't think contact welding makes sense because once I break it free it will happily connect/disconnect the load.
Only after sitting for a month does it get stuck.

You might be in to something. I've never run a contactor past hours, I'm just struggling to see how/why it gets stuck.

It still feels like welding/arcing and the related damage. Maybe it's the arc and welding debris getting stuck with the heating and cooling cycles from running 250 amps through the junk on the contact points.

I liked the idea of a contactor because in theory it was "fail open" vs the shunt trip requiring my bms to be functional to work.
Leaning towards going back to a shunt trip after this.

 

[justinjja]

I say no precharge, but I always power up the inverters from the grid first and then connect the batteries.
Assuming it's not a bad reading the growatt says the battery is sitting in the low 40v's after powered on without a battery.

I should check that with a DMM the next time I'm down for maintenance.

 

[Pyrofx]

If you charge from grid first . I'd say shit contactor.
But....... if you did battery first. even once. the deal is done.
Kilovac has a white paper on this .

 

[400bird]

If you charge from grid first . I'd say shit contactor.
But....... if you did battery first. even once. the deal is done.
Kilovac has a white paper on this .

Could you help me find that white paper?

 

[Pyrofx]

Still looking. Buts here's one of the emails.
Please see my comments below:

We see this frequently with inverter pre-charge circuits and it’s a mis-application of our contactor.

Based on experience with automotive and other inverter systems (converting DC battery power to AC for the motors), the weld failure is ALWAYS caused by insufficient pre-charge of the capacitors prior to closing the mains (LEV200 or LEV100) relay contacts.

Be sure that the capacitors are pre-charged enough BEFORE the main contacts are closed. In the development phase, monitor the capacitive current inrush spike (with oscilloscope) to learn how precharge time affects the current spike. They must keep it below 650A, and it shouldn't be more than about 250A nominally (this is for LEV200…..If they're using LEV100 it should be more like 100A nominal cap inrush….600A max).

Once enough pre-charge is established, the issue will be resolved.

Depending on the severity of the weld, this might work: Try cycling the contactors 20-30 times. Sometimes this is enough to break the weld. If that doesn’t work, try a mild but forceful “bang” of the bottom of the contactor to the ground or hard surface. to try and free the welded contacts. If it opens, cycle it 20-30 times to flatten the rough surface where the weld was.

If none of this opens the contactors, then it’s a hard weld and of no real use. These can’t be repaired.

Don´t hesitate in contacting me if you need anything else.

I'll be looking forward to your answer.