bloobloo
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Looks confusing! how would they wire up?
- Thread starter bloobloo
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Seadog
Save the planet. It's the only one with rum!
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1 x 70HFR120 70A/1200V metal stud type rectifier di sq | eBay
PART NUMBER: 70HFR120. HIGH POWER RECTIFIER. HIGH SURGE CAPABILITY. 70 AMP, 1200 VOLTS.
www.ebay.co.uk
1 x 70HF120 70A 1200V High power rectifier metal stud type rectifier diodes OIUK | eBay
Part Number: 70HF120. HIGH POWER RECTIFIER. HIGH SURGE CAPABILITY. 70 AMP, 1200 VOLTS.
www.ebay.co.uk
These are 70A devices, so 4 of each necessary (stud anode and stud cathode). About £32.
Conceptually it's a simple idea, paralleling like any component, but yes... the execution is messy!
I did a couple for the challenge, I doubt I'd do it again.
This thread describes it well:
Replacment Rectifier for MIG Welder
I have a 250 Amp single pahase Mig Welder which had a diode short circuit in the rectifier. The replacement rectifier was available but...
www.boatdesign.net
bloobloo
Professional Tinkerer
- Messages
- 271
- Location
- Ashton in Makerfield, Wigan UK
A spider seems to have fallen into some ink and then dried itself off on your notepad
This article describes how to parallel bridge rectifier blocks:
www.boatdesign.net
Replacment Rectifier for MIG Welder
I have a 250 Amp single pahase Mig Welder which had a diode short circuit in the rectifier. The replacement rectifier was available but...
www.boatdesign.net
bloobloo
Professional Tinkerer
- Messages
- 271
- Location
- Ashton in Makerfield, Wigan UK
5 Pairs Rectifier Diode Spiral Module for Battery Charging 70HFR120/70HF120 | eBay
<li> Feature:</li> <li>1. The rectifier diode has high surge current capability 2. The chassis is mounted with studs for easy installation 3. High quality material can make sure the durability and stability of the product 4. Small body, great replacement for the old or damaged one. 5. Suitable...
www.ebay.co.uk
Too good to be true?
Good price and better spec than the 25A versions you saw earlier. Still buy two sets as @Seadog says.5 Pairs Rectifier Diode Spiral Module for Battery Charging 70HFR120/70HF120 | eBay
<li> Feature:</li> <li>1. The rectifier diode has high surge current capability 2. The chassis is mounted with studs for easy installation 3. High quality material can make sure the durability and stability of the product 4. Small body, great replacement for the old or damaged one. 5. Suitable...www.ebay.co.uk
Too good to be true?
Check the continuity of the secondary first with your meter and identify the A and B windings. They should both be very low resistance and not connected to each other. Label one of the windings as A0 and A1, leave the B winding alone for the moment.
Check the resistance of the primary windings. Make sure you have continuity from the ends of the windings. Note the readings.
Bolt the transformer in and put the wires back to the power switches as they were before. I'd also recommend removing that soldered 1/4" crimp terminal and crimping it off properly. If you can, fully sleeve each of the primary wires as well, it's all safety and reliability in the future.
Test the mains side with your meter to make sure there are no shorts and you have continuity on all settings and then plug it in and see what happens. You're looking for 0 Ohms from the earth pin to the chassis. 0L or open circut from the earth pin to the live and neutral pins.
Then check the transformer primary, you will need to measure at the back of the switches, connect the meter on ohms range to the central two pins of the voltage setting switches and note the resistance, as you change the switches, the resistance should change as the different dindings are switched in/out. These will be low ohm readings but should correspond to the readings you noted above.
If it all adds up, then think about powering it up
When it doesn't blow fuses/catch fire we can look at sorting the secondary and the rectifier out
Each diode will pass 70A comfortably so you need two to pass 140A that your welder is capable of. But this is working current, if you hvae a short or other fault, the current could go well beyond 140A. You could get by with four diodes and have two spare but you have no overhead. Theoretically, they will probably go behond 140A for quite some time - the current rating is continuous but they only conduct for one half of the cycle and have half a cycle for recovery. You need to balance the bridge as well, you should't have 3 diodes in parallel on one leg and two diodes in parallel on the other leg so you are going to be left with one pair of diodes.
Buying two sets gives you twenty diodes so you will be able to use three or four on each leg and so give yourself less chance of burning out the diodes.
Finally, we don't know anything about the existing diodes, they could be 70A or they could be 100A and the rectifier is definitely better over engineered than under.
D
Definitely. The one that's in is a full wave bridge rectifier, make sure the Ali-Express is the same.
You can re-assemble your old one and leave the burnt out diodes out in the meantime and connect it all back together to test everything as well. I wouldn't recommend welding with only half the diodes in but you should be able to test the ouput voltages, wire feed etc. and be confident that it will work fine when a new rectifier arrives.
bloobloo
Professional Tinkerer
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- Ashton in Makerfield, Wigan UK
Apart from all the faffing about, is there any reason why I couldn't use these to rebuild the rectifier? I can order 4 off Amazon for about £7- £8. *(be here tomorrow) Would I need 4 or 8?You could test the transformer and the lower voltages using one of these.
BEN KBPC5010 1000V 50A Bridge Rectifier.
bloobloo
Professional Tinkerer
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- 271
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- Ashton in Makerfield, Wigan UK
Well I ordered 8 of them. I'm sat waiting for the Amazon delivery guy to bring me my prezzies!
I have some 150mm aluminium channel that I am going to use as a heatsink and a spare computer fan and heatsink that I will attach to the channel. Thermal paste will be applied behind all the diodes and between the Pc heatsink & fan.
I have a roll of 5mm multi strand copper earth wire that I am thinking of using to wire the diodes with = onto some sort of copper bus-bar, probab;y a piece of copper pipe squashed to suit.
Hopefully a productive day if the Amazon guy gets here soon!
All the bridge rectifier blocks should be mounted as close together as possible, on a heatsink thick enough to ensure that they are all at the same temperature.
As long as they are adequately-sized for the expected current ( 5mm2 would be fine ), the leads do not have to be especially short, some resistance helps with current balancing. However, all the wires must be exactly the same length, so for 8 blocks you need to cut 32 identical pieces of wire.
One end of each group of 8 wires needs to be crimped and soldered to a common point - which can be flattened copper pipe. There will be four of these common points. If you have tight and well-crimped spade tags, they can be used to join to the rectifier tags. Otherwise, a fast soldered joint with a large temperature-controlled iron is preferable.
As long as they are adequately-sized for the expected current ( 5mm2 would be fine ), the leads do not have to be especially short, some resistance helps with current balancing. However, all the wires must be exactly the same length, so for 8 blocks you need to cut 32 identical pieces of wire.
One end of each group of 8 wires needs to be crimped and soldered to a common point - which can be flattened copper pipe. There will be four of these common points. If you have tight and well-crimped spade tags, they can be used to join to the rectifier tags. Otherwise, a fast soldered joint with a large temperature-controlled iron is preferable.
