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AC Power over tether


(Basil Alias) #1

HI,
We are planning to power ROV using an External power supply using an Ac to DC converter inside the ROV instead of a battery. So, is it possible to supply AC voltage(230v @ 6Amps) through twisted pairs by combining 3 pairs(2 Amps on each pair) parallelly??
@adam


(Bo Koppel) #2

I do similar solution, 2 amps 240V AC on two pairs, one pair phase, one pair neutral in 100 m tether.
Using 25A converter onboard and current limiting in ROV parameters.

NOTE!! really dangerous regarding electric safety even with GFCI breaker !!


(Basil Alias) #3

Thankyou Koppel


(Michael) #4

What power supply are you thinking of using? I am looking into this also.
Thanks


(Bo Koppel) #5

The budget 25 Amp has to be cut a bit in the corners (!!!), but works very good:
https://www.aliexpress.com/item/2016-New-SANPU-SMPS-12V-LED-Power-Supply-Unit-300W-25A-AC-to-DC-Lighting-Transformer/32719958441.html?spm=a2g0s.9042311.0.0.28664c4dK4huDn

If You not like to cut a 240 V Powersupply (You really shouldnt) there is 16 Amp that fits right off:
https://www.aliexpress.com/store/product/2016-New-SANPU-SMPS-12V-LED-Power-Supply-Unit-200W-16A-AC-to-DC-Lighting-Transformer/1470529_32716049336.html?spm=2114.12010612.8148356.44.53b360c4H2iOQv


(Basil Alias) #6

Actually, we are looking for a power supply which delivers a power of more than 1500W. So, we have to send 230/240V AC supply from the surface and to put (230)AC-DC (16V)converter inside the ROV (considering the voltage drop in 300 meters). @Boko


(Oystein Skarholm) #7

240v 1500w. You will need one big tether! I am upgrading from 400v to 600v due to voltagedrop in 300m tether…New supply will be 600/24 volt 50amp 24volt in the bottle.


(Bjarte Langeland) #8

Hello Øystein. 24V@50amps will give you 1200W. Will this be sufficient for the 8 thruster configuration? What kind of modification/ replacement of the components is needed in the bottle?


(Oystein Skarholm) #9

The “new” ECS and the Lumen lights and motors are ready to go with 24 volt. U only need a BEC transforming 24 to 12 volt. Feed the 12volt into the remaining electronic parts just as you would do with the battery.
1200watt is sufficient depending on the use. Due to voltage drop over a 300m tether and 2.5Amp supply, the voltage subsea will be approx 565VDC (4x21AWG)
This in turn will give a potential of drawing 1400watt + , if I expand the DC/DC converters.
But I would argue that horizontal movement and vertical movement rarely happens at full gain simultaneously.
So for 4 horizontal thrusters running at 50% gain (4x350w/2)=700watt, still leaves enough power to run the 4 vertical thrusters at 35% gain ((1200-700)w/4/350wx100)=35,7%.
Not too bad I would say. ?


(Adam) #10

Hi,

Just a minor correction- the T200 is NOT rated to run at 24 V, and is only officially rated for up to 20 V. Running a T200 at over 20 V is unsupported, but you are welcome to try on your own. For a more complete explanation please see my response here:

There is nothing on the BlueROV2 that runs at 12 V, the two UBECs step down from battery voltage to 5 V to power the Pixhawk, camtilt servo, Bar30, Raspberry Pi, and camera. The Fathom-X and ESCs all run at battery voltage (up to 27 and 25.2 V respectively). Its true the UBEC we have been using on the BlueROV2 until recently can in theory handle up to 25.2 V input, but its extremely hard on them. Using another 24-12 V adapter before and feeding this to the UBECs instead can work, but a better solution would be to use a more powerful UBEC on its own that can better handle higher voltages and currents, like the new one we are now including with the BlueROV2.

Out of curiosity, I have tested the Blue ROV2 with a 6S battery (22.2 V nominal, 25.2 V max) with both the old and new UBECs. The new UBECs are definitely recommended if exceeding the BlueROV2 operational voltage like this. All the electronics handled the higher voltage surprisingly well, including the R3 ESCs. However, after extended use at constant full throttle, I was able to overheat and damage a couple thrusters as expected. If you choose to run the BlueROV2 at beyond its operational voltage, it would be best to keep full throttle bursts at 100% gain to short periods at most, or perhaps limit gain altogether to 75% or so.

-Adam


(Oystein Skarholm) #11

I should off course emphasized that deviating from the original BR2 set-up is done at own risk, but that goes without saying, really. Running the motors on 24 volt on full gain over time is not good. However, I would argue, that is not how ROV operations are performed either, We normally go in low gain but if current creates a drag than the gain need to go up as well. Running the system on a lower voltage will be better for the thruster, but the current will increase and hence the heat in the ESC (my experience). So therefore I choose to up the voltage to 24volt to minimize the amp and heat in the circuit as the cooling is passive. Now it remains to see if my approach is correct since I am still awaiting the 600/24 DCDC converters.
Now, let at least this be stated: Electrical shock may lead to injury or death. 600Volt 2,5A can easily kill you!!! DO NOT temper with electricity if you lack the knowledge of safety. Also, to be clear, I am not using BR tether for power over tether. make sure the tether its rated for the voltage and current planned for the system and always, always have a ground fault breaker, dealing with voltage @ 30Volt AC and 130VDC, may, in worst case, be lethal.
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Battery charger on sub?
(rohit ) #12

hi
you try this thing then tell me how to do that .

thanks
@SDI @Boko