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MrFluffy
04-15-2018, 02:19 PM
I need a cob style led chip + separate transformer to replace a old LoVo light setup on my surface grinder as the transformer has gone in the lovo housing and I'm on my last low voltage incandescent machine lamp bulb anyway, and the bulb holder is trash too. I run the grinder with suds most of the time, so it has to be low voltage for safety.

I can site a chip style led transformer inside the lovo housing where the original lovo transformer lived, and have low volt wiring up to the machine light itself and swap out the holder for a led chip using the original wiring, trouble is, the machine has no neutral connection in its wiring closet, and is 3phase. So "mains" voltage into the lovo transformer housing is 400v in this case.

I've gone through my little cob + transformer stash, and all of them are rated on their label as 100-280v so I imagine feeding one 400v might be detrimental to its short term life let alone a long term one, has anyone found any on the usual sites for the same with 20 or 30w cob led chip but will take higher input voltages without letting the magic smoke out?
If push comes to shove, I'll add a neutral into the machine itself and use one of these to give me 230v instead, but it means new wiring, plug etc, so if I can just buy the right thing instead it might be easier, plus I have some other machines that could do with the same too.

Regards
MrFluffy

J Tiers
04-15-2018, 02:25 PM
What voltage are the machine controls?

Usually they are not run on 400V. If they are run on a lower voltage, then your issue becomes simpler, start with the lower machine control voltage.

MrFluffy
04-15-2018, 04:34 PM
The machine itself just has a go and stop contactor which runs 380v, and everything else runs on hydraulics, so not sure I have any low voltages to tap. Digging through stash to see if I can transform the 380 down into something I can feed the cheap cob driver transformers instead as the current option.

J Tiers
04-15-2018, 05:06 PM
Well, a 480 to 120V transformer will produce 100V if used with that. Not sure where you are, so some may be more available than others in your location.

Paul Alciatore
04-15-2018, 11:51 PM
First I would go for a 24 V circuit, not 115 V.

24 to 28 Volt, cob LEDs:

https://www.digikey.com/products/en/optoelectronics/led-lighting-cobs-engines-modules/111?k=cob+LED+&k=&pkeyword=cob+LED+&pv319=1365&pv319=1021&pv319=1228&pv319=1429&pv319=994&pv319=1368&pv319=1220&pv319=1170&FV=2dc1dab%2Cffe0006f%2C1f140000&quantity=0&ColumnSort=0&page=1&stock=1&pageSize=25

480V to 24V transformers:

https://www.mouser.com/Power/Transformers/_/N-8u9mo?P=1yzvc7dZ1yzsn7cZ1yzs0d9Z1z0wd3eZ1yzs0d8Z1y ctg26&Keyword=transformer&FS=True

You will need to rectify the AC transformer output to DC for the best results. And be sure to match the current requirements of the LED you choose to the transformer's rating.

But I would use a power supply instead of a transformer. With a regulated, DC power supply, you get the exact Voltage needed and they are highly efficient. So your LEDs should last for their rated life. DC power supplies, 24 V:

https://www.digikey.com/products/en/power-supplies-external-internal-off-board/ac-dc-converters/133?k=power+supply&k=&pkeyword=power+supply&pv1525=148&FV=ffe00085%2C1fc0689%2C1fc11de%2C1fc1823%2C1fc027 e%2C1fc1945%2C1fc1ba8%2C1fc1bb0%2C1fc1bdd%2C1fc1be 4%2C1fc1c3d%2C1fc1c7b%2C1fc1c84%2C1fc1c90%2C1fc1cc d%2C1fc1d03%2C1fc1d06%2C1fc1d1d%2C1fc1d40%2C1fc1d7 a%2C1fc1d88%2C1fc1d89%2C1fc1d8a%2C1fc1d8b%2C1fc1da b%2C1fc1dac%2C1fc1dad%2C1fc1dae%2C1fc1daf%2C1fc1db 4%2C1fc1dc2%2C1fc1de7%2C1fc1dff%2C1fc1e02%2C1fc1e0 6%2C1fc1e07%2C1fc1e10%2C1fc1e15%2C1fc1e20%2C1fc1e3 c%2C1fc1e3d%2C1fc1e49%2C1fc1e6d%2C1fc1e72%2C1fc1e7 9%2C1fc1e7a&quantity=0&ColumnSort=0&page=1&pageSize=25

Good luck.

J Tiers
04-16-2018, 12:48 AM
That's the reason for using 100/115V..... there are so many regulated supplies that accept that (or 230V, in UK, where the OP may actually be located, IIRC.

MattiJ
04-16-2018, 01:32 AM
First I would go for a 24 V circuit, not 115 V.

24 to 28 Volt, cob LEDs:

https://www.digikey.com/products/en/optoelectronics/led-lighting-cobs-engines-modules/111?k=cob+LED+&k=&pkeyword=cob+LED+&pv319=1365&pv319=1021&pv319=1228&pv319=1429&pv319=994&pv319=1368&pv319=1220&pv319=1170&FV=2dc1dab%2Cffe0006f%2C1f140000&quantity=0&ColumnSort=0&page=1&stock=1&pageSize=25

480V to 24V transformers:

https://www.mouser.com/Power/Transformers/_/N-8u9mo?P=1yzvc7dZ1yzsn7cZ1yzs0d9Z1z0wd3eZ1yzs0d8Z1y ctg26&Keyword=transformer&FS=True

You will need to rectify the AC transformer output to DC for the best results. And be sure to match the current requirements of the LED you choose to the transformer's rating.

But I would use a power supply instead of a transformer. With a regulated, DC power supply, you get the exact Voltage needed and they are highly efficient. So your LEDs should last for their rated life. DC power supplies, 24 V:

https://www.digikey.com/products/en/power-supplies-external-internal-off-board/ac-dc-converters/133?k=power+supply&k=&pkeyword=power+supply&pv1525=148&FV=ffe00085%2C1fc0689%2C1fc11de%2C1fc1823%2C1fc027 e%2C1fc1945%2C1fc1ba8%2C1fc1bb0%2C1fc1bdd%2C1fc1be 4%2C1fc1c3d%2C1fc1c7b%2C1fc1c84%2C1fc1c90%2C1fc1cc d%2C1fc1d03%2C1fc1d06%2C1fc1d1d%2C1fc1d40%2C1fc1d7 a%2C1fc1d88%2C1fc1d89%2C1fc1d8a%2C1fc1d8b%2C1fc1da b%2C1fc1dac%2C1fc1dad%2C1fc1dae%2C1fc1daf%2C1fc1db 4%2C1fc1dc2%2C1fc1de7%2C1fc1dff%2C1fc1e02%2C1fc1e0 6%2C1fc1e07%2C1fc1e10%2C1fc1e15%2C1fc1e20%2C1fc1e3 c%2C1fc1e3d%2C1fc1e49%2C1fc1e6d%2C1fc1e72%2C1fc1e7 9%2C1fc1e7a&quantity=0&ColumnSort=0&page=1&pageSize=25

Good luck.

Current.
You should be using current regulated or constant current power supply, constant voltage is BAD way to drive those LEDs.

Some chinese COB boards pack the "integrated smart ic" ;) power supply to same COB board with the leds, but I haven't seen 24v models. Only 110 or 230v input
https://www.ebay.com/itm/30W50W70W100W-200W-LED-Chip-220V-Input-Integrated-Smart-IC-Driver-Floodlight-COB/162819481232?hash=item25e8cc1e90:m:mCPfOFbcbFKOyIB Ci0tlxnQ

darryl
04-16-2018, 01:59 AM
Comes to mind that if you use a transformer to begin with, you can end up with an isolated secondary. Even though still a high voltage, like 150vdc after rectification, it has less shock potential. There are cob led decks that have their own current regulator and are designed to run from 110 vac or higher. You have isolated voltage, but still high so maybe it's still a no-starter. But it's pretty simple, just the led deck and the transformer.

You're likely going to be using the step down transformer anyway, so the next simplest is to add as few parts as possible between the led array and the transformer. How much led power are you thinking about anyway? I don't recall anyone suggesting what wattage level we're dealing with.

MrFluffy
04-16-2018, 03:16 AM
I have 10,20 and 50w cob led + drivers on the shelf already in 100-280v versions. These come with a separate cob chip and a driver unit, so you can locate the driver inside and feed it "normal" mains voltages, but it emits low volt 24v dc into the cob chip via its wiring.
I've done a few machine lights with this layout already, locating the driver part inside the machine base with other electrical components & using the existent wiring on the machine between base and lamp and swapping the bulb holder for a heatsink and the cob chip to move from defunct original lovo setups, but this machine is a bit awkward because its 3 phase with no neutral to pick up a 230v single phase feed from to run things. On deeper reflection I may bite the bullet and change the wiring to it and rewire the lockout and plug etc because I also want to eventually fit it with a DRO when funds allow, and that will have the same issues.
Given how generic and wooly the spec's are on these things are, It may even be possible to feed 380v to something rated at 280v max on its print label and it cope, but ignoring spec's seems like a bad thing in general to get into, even with chinese spec's...

Holy grail would have been someone who's had the same issue chiming in saying "hey, this brand from xyz can cope with higher input voltages" and it be silk-screened or printed onto the label of them.

Paul Alciatore
04-16-2018, 03:53 AM
If an LED ASSEMBLY is designed to run on a specific Voltage, then a Voltage regulated supply is just fine. We are not talking about naked LEDs here which would operate in current mode and somewhere between 1.5 and 3 Volts. A 24 Volt LED assembly, such as a COB, will have it's own current regulation and be just fine with that Voltage.




Current.
You should be using current regulated or constant current power supply, constant voltage is BAD way to drive those LEDs.

Some chinese COB boards pack the "integrated smart ic" ;) power supply to same COB board with the leds, but I haven't seen 24v models. Only 110 or 230v input
https://www.ebay.com/itm/30W50W70W100W-200W-LED-Chip-220V-Input-Integrated-Smart-IC-Driver-Floodlight-COB/162819481232?hash=item25e8cc1e90:m:mCPfOFbcbFKOyIB Ci0tlxnQ

MattiJ
04-16-2018, 04:01 AM
Given how generic and wooly the spec's are on these things are, It may even be possible to feed 380v to something rated at 280v max on its print label and it cope, but ignoring spec's seems like a bad thing in general to get into, even with chinese spec's...

Holy grail would have been someone who's had the same issue chiming in saying "hey, this brand from xyz can cope with higher input voltages" and it be silk-screened or printed onto the label of them.

100% guarantee that it is going to blow up if connected to 400v instead of 240v.

Easiest way is to add small transformer(s) to supply lower voltage at xx volts.
If you have stash of 230v transformers you can connect two of those in series for 400v operation.
2pcs 230v-->110v transformers with primaries in series and secondaries in parallel would give you 95vac on secondary. Lots of switch mode power supplies and led drivers available with input voltage range starting at 90vac.

PStechPaul
04-16-2018, 06:11 PM
There are switching supplies rated for 480 VAC input, but they are usually three-phase and rated in kW, with cost over $1000.

You may find DC-DC converters rated for EVs which may have input as high as 800 VDC, but they are also several hundred watts and dollars to match, although some may be available as salvage.

There are also DC-DC converters rated for 100-1000 VDC input, with outputs of 5,12, and 24 VDC, and power of 5, 10, 15, and up to 40 watts, for about $60-$120:
https://www.mouser.com/Power/DC-DC-Converters/Isolated-DC-DC-Converters/_/N-brwkv?P=1y986a8Z1y97o92Z1z0j067Z1y986a5Z1yqwp1gZ1y 9eb27Z1y9eb26&Keyword=DC-DC+converter&FS=True&Ns=Pricing|0

Most control and machine tool transformers are available with 240/480 primaries, and power of 50-1000 watts, but tend to be heavy, bulky, and expensive for new units. Used ones might be pretty cheap and usable.

It is possible to use two similar transformers with 240 VAC primaries wired in series, and secondaries in parallel, to divide the primary voltages equally.

Two identical 85-265 VAC switching supplies might be wired with inputs in series, but you may need to add external balancing resistors or power zeners on their input capacitors to assure balance at start-up. The outputs in parallel on the load will usually cause equal current draw on the inputs to balance voltages.

Here is a 60 watt power supply with 24 VDC output rated for 480 VAC input (three phase), for $59:
https://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_(Electrical)/DC_Power_Supplies/24VDC,_3-Phase_Input/PSB24-060S-3

They also have a 50 VA 240/480 primary 120/240 secondary control transformer for $40:
https://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_(Electrical)/Power_Transformers/1-Phase_Compact_Control_Transformers/480x240_VAC_to_240x120_VAC/PH50MQMJ

Another idea would be using a transformer with a high voltage secondary in reverse. Old TVs and radios often had plate voltages of 400-600 VDC produced by transformers, so you might find one with 300-0-300 VAC or 600V, so at 480 VAC on secondary it would provide about 95 VAC on the primary.

Miscellaneous ideas:

https://www.ebay.com/itm/AS-2T230-200VA-230V-460V-CT-6-3V-x2-Tube-Amp-Power-Transformer/371663807251

https://www.ebay.com/itm/AS-1T250-100VA-250V-500VCT-6-3V-x2-Tube-Amp-Transformer/372195217634

https://www.ebay.com/itm/120-208-240-480-Volt-to-24-Volt-50VA-Foot-Mount-Transformer-Manual-Reset/122827679666

https://www.ebay.com/itm/ZETTLER-AHR40314FMW-139-RHEEM-46-100836-03-40-VA-TRANSFORMER-480-VOLT-171486/360757587554

https://www.ebay.com/itm/General-Signal-Hevi-Duty-1Ph-240-480-Primary-Volts-120-240-Secondary-Transformer/332622434099

https://www.ebay.com/itm/CUTLER-HAMMER-C340CNG-CONTROL-TRANSFORMER-0-050-KVA-220-480-VOLTS-PRIMARY/222727978947

MattiJ
04-17-2018, 03:30 AM
Two identical 85-265 VAC switching supplies might be wired with inputs in series, but you may need to add external balancing resistors or power zeners on their input capacitors to assure balance at start-up. The outputs in parallel on the load will usually cause equal current draw on the inputs to balance voltages.

Imbossibru.
This sounds like disaster. This is a unstable combination that is doomed to fail because of imbalance in input side. This would work with unregulated power supplies like transformer but not with your typical SMPS.
Because of the internal regulation in the power supplies they output roughly constant output power but the one with even a fraction smaller input voltage is going to (attempt to) draw larger input current. Larger input current leads to further voltage imbalance and that causes again increased current demand from primary. Unregulated SMPS would work but those are not too common.

PStechPaul
04-17-2018, 04:46 AM
Yes, I see what you mean. For a fixed load, a PSU will draw more primary current as the voltage is reduced, so its impedance will drop. A resistive voltage divider or zeners would be inefficient. Also, regulated supplies with outputs in parallel may "fight" each other, where the one with slightly higher output voltage will tend to supply all the load current, perhaps until it reaches an overcurrent limit shut-down. Isolating the outputs from each other with diodes will help some, but still not a good solution.

If you have a transformer with two 240 VAC windings, you might be able to connect them in series as an autotransformer to provide a center tap on a 480 VAC source, and then two 240 VAC supplies could be used, one on each winding. There is still the problem of outputs in parallel, but you could use two 12V outputs in series to get 24 VDC.

Paul Alciatore
04-17-2018, 01:42 PM
Cost over $1000? I guess you did not check out the link to DigiKey that I posted above. Here is a 5 Amp supply that runs on single phase or on one of the three phases in a three phase supply.

https://www.digikey.com/product-detail/en/mean-well-usa-inc/WDR-120-24/1866-1088-ND/7707216

DigiKey's price is $65.

There were over 100 supplies in that link. When I narrowed the search down to 5A supplies I was still at about 25 to choose from, many of which were under $100.

The building of ever better and ever less expensive power supplies (AC to DC) is one of the hot areas of electronics today. Prices for switching supplies are really reasonable. BTW, that $65 price from a top line supplier like DigiKey tells me that you can probably find similar items on the web for half that amount or even less. I guess the military and GM will pay $1000 or more, but certainly not I.




There are switching supplies rated for 480 VAC input, but they are usually three-phase and rated in kW, with cost over $1000.

You may find DC-DC converters rated for EVs which may have input as high as 800 VDC, but they are also several hundred watts and dollars to match, although some may be available as salvage.

...<snip>...

MattiJ
04-17-2018, 04:02 PM
If an LED ASSEMBLY is designed to run on a specific Voltage, then a Voltage regulated supply is just fine. We are not talking about naked LEDs here which would operate in current mode and somewhere between 1.5 and 3 Volts. A 24 Volt LED assembly, such as a COB, will have it's own current regulation and be just fine with that Voltage.

ALL of the COB led's YOU linked from digikey need to be used with constant current supply.
As an example the datasheet from Bridgelux COB:
https://www.bridgelux.com/sites/default/files/resource_media/Bridgelux%20DS92%20Vero%2018%20Gen%207%20Array%20D ata%20Sheet%2020170627%20Rev%20J.pdf

BXRC-xxx400x-D-7x model worst-case drive voltage at 1amp: hot 25,8v and cold 32v
Driving one at constant voltage would result very dim led or burnt led depending on temperatures and product variation.