Wow well I appreciate that. I've wanted to get into using Arduinos but I have not had the time to get into them. It would also take me a while to figure out the schematic you provided because I'm not very familiar with electrical schematic symbols but I'm sure I could sort through. Would you mind giving a brief explanation on what exactly you created there. Also is this something you've created or used before?

 

I'd be very wary of Jayanthd's solution. It's not possible to convert a single phase AC to a full-wave 3 phase with just triacs. At best it's going to be small chunks of cycles and while a small motor might be OK with it a big transformer is unlikely to be.

I'd like to see the input and output waveforms on load as a starting point

I've used 1ph-to-3ph inverters extensively for motors but they invariably change the frequency as well as reduce the voltage at lower speeds. The outputs are a trapezoid shape rather than a true sine wave. I did have one older one that was a true sinewave output at line frequency and could be configured as fixed voltage. That would certainly have worked.

As you're an automotive shop maybe you could source a single-phase motor and 3phase generator and fabricate your own generator set..

 

Single phase motors no problem. 3ph generator head that's not a common thing for me to come by. I was reading about a diy rotary phase converter using a large 3ph motor. I can probably come up with a decent 3ph motor.

 

The block diagram that you had provided showed 220V 1PH AC input and 220V AC 3PH output into 3PH motor.

My circuit is very simple. I assume that 1PH NEUTRAL will be the NEUTRAL for the 3PH motor if needed...

So, the 229V 1PH LINE goes to the 3 triacs and when ZC is detected then 1st triac is fired at ZC and then after 60 degrees that is (50hz and so 180 degrees is 10ms and 60 degrees is 3.3333ms)
After 3.333ms the 2nd triac is fired and after next 3.333ms 3rd triac is fired.

So, 0ms, 3.333ms, 6.67ms (3.333ms + 3.333ms)

0, 60, 120 degrees are the firing angles

Then the same firing pattern is repeated every ZC.

 

Have you actually tested this for real on any large scale system? It will be totally unbalanced. Phase A gets the 1st 1/3rd of the cycle starting at zero volts. For a resistive load that's OK, but for an inductive load that's a current maximum = huge inrush current. Equally bad phases A and C get only the runt ends of the cycle, while B gets the bigger middle portion. Can you imagine what that might do to a motor? It won't be good, lots of vibration at the very least.

Oh and by the way, Triacs can't be turned off in the middle of a cycle; once on they stay on till the current through them drops to zero. So you can't have tried this for real. Or maybe you expected all phases to end at the next ZC. Well that's not 3-phase, the overlaps at both ends of the cycle are important.

Good try my friend, but if it was that easy don't you think it would be common practice by now? You have a lot to learn about power engineering and circuit design.

 

Have you actually tested this for real on any large scale system? It will be totally unbalanced. Phase A gets the 1st 1/3rd of the cycle starting at zero volts. For a resistive load that's OK, but for an inductive load that's a current maximum = huge inrush current. Equally bad phases A and C get only the runt ends of the cycle, while B gets the bigger middle portion. Can you imagine what that might do to a motor? It won't be good, lots of vibration at the very least.

Oh and by the way, Triacs can't be turned off in the middle of a cycle; once on they stay on till the current through them drops to zero. So you can't have tried this for real. Or maybe you expected all phases to end at the next ZC. Well that's not 3-phase, the overlaps at both ends of the cycle are important.

Good try my friend, but if it was that easy don't you think it would be common practice by now? You have a lot to learn about power engineering and circuit design.

If 3PH motor has to run for say 2 hours then why the TRIACs needs to be turned off in the middle? And my system has ACS7xx CS on all the converted phases using modular CBs and when the motor has to be turned off then the Arduino will stop monitoring the ZC or it will stop the firing of the 3 triacs.

 

It seems that it works. I will do more tests. There is simulation issues which is not letting me to fully simulate. If minor changes needed in the L and N connections into the three TRIACs then I will try that also. I am very sure that I can make it work 200%.

 

Simulation != real world especially where high power and electromagnetics are concerned, at least not in most simulators out of the box.

So far your simulation is only showing the gate pulses; that's trivial, we need to see the U V, W signals.

In any case, I can't see how you are going to get 3 AC sine waves offset 120deg (NOT 60) out of one cycle with just triac switches.

I think you are clutching at straws, but I'll be the first to applaud if you prove me wrong. 200% huh? Well I admire your confidence!

 

Simulation != real world especially where high power and electromagnetics are concerned, at least not in most simulators out of the box.

So far your simulation is only showing the gate pulses; that's trivial, we need to see the U V, W signals.

In any case, I can't see how you are going to get 3 AC sine waves offset 120deg (NOT 60) out of one cycle with just triac switches.

I think you are clutching at straws, but I'll be the first to applaud if you prove me wrong. 200% huh? Well I admire your confidence!

Input is 220V 50 hz 1ph sinewave. The first triac starts output at the detection of 1st ZC. So, left most triac in the circuit has 1:1 output , that is same as input ACV. 2nd triac fires at 120 degree completion of primary ACV and 3rd triac fires at 240 degrees of primary ACV. 50hz and so 50 cycles per sec. If 2 cycles have distorted signal then no issues. From the 3rd cycle of the 50 cycles per sec the 3ph sinewaves will be continuous.

Yes, it is 0, 120, 240 degrees switching. The 0, 60, 120 degree was an error made while I was working on 3 to 4 different project designs.

 

hi jay,
This LTspice simulation is from your description.
How do you claim to get 3 Phases of usable current.?

If I have followed your description correctly, your 'idea' is seriously flawed.

E

 

I have the right idea. It needs a couple of additional power switches with a small piece of extra code. I will do that in a few hours when I get back to my PC.

 

a small piece of extra code

Hi,
That will not get the result you claim.
You will have to time shift the original 50Hz Sine wave by 120deg and 240deg, if ever you hope to create a true 3 Phase Current.

E

 

If 2 cycles have distorted signal then no issues.

Err, many issues. Most 3-phase devices will be very unhappy with that, it's too unbalanced.

Anyway, as @ericgibbs has shown (you beat me to it!) it just doesn't work. You can't create time-shifted energy out of thin air... The incoming single phase is all you have to play with; at the times you need energy in the other phases it's not present at the input. QED it can't work! No amount of tinkering with code can change the laws of physics...

 

So anyways. What I've been reading is that people are using large 3ph motors to convert 1ph to 3ph. Running 230v single phase in and starting the motor with either a static phase converter or a smaller single phase motor. After starting everything except the 3ph motor is switched off so now the 3ph motor is running off single phase but it is able to have an output on the 3rd leg that was previously not used. Then running 3ph equipment wired parallel off of that. Now I've watched examples of this working but does anyone care to tell me exactly what's happening. It has to be outputting a nice sine wave from what I gather but does it do it nicely 120 apart? I don't understand how you tie into the single phase input and have the phase shift right there. If it is the case can it disrupt back to the mains and cause any other 230v 1ph to be 120 apart vs 180?

 

A 3ph motor can't start on 1ph without help (i.e a start capacitor) but once running can continue to rotate on 1ph. Once it's rotating the undriven windings, which are electrically at 120deg and 240deg from the driven winding, will individually generate output in the correct phasing. The input power is 1.73 x output power + power to turn the motor, which could be a further 20%.

So for a 3.6kW charger you need 4kW 3ph (say 110v @ 21A/phase) which will require 5kW input, eg 110v @ 45A or 220v @ 23A.

 

Personally I'd consider buying a proper 1ph to 3ph pure sine wave inverter such as this one. It'll drive a transformer load.

 

Honestly I can tell you I won't be able to swing that expense. Not that we physically can't but the forklift is an occasional luxury for us. Not going to talk the owner on dropping another grand on anything for it. So since there is no economical way to hook that 3ph charger up I'll probably list it for sale and see what I get. From there I can decide what direction I go. I started another thread about using a solar charge controller and 12v psus but no one replied. I can put a 60amp setup together for maybe a few hundred dollars. I may ask about it on a hobby forum. I've seen threads from people using 48v from these psus into lipo charge controllers drawing high amps. I want to go 1 more and make it 60v.

 

What do you actually need the charger to output? And what battery technology?

 

Lead acid deep cycle battery. 36v. It's a 750ah battery. Already confirmed that 21 amp charger I have is enough to start gassing it to mix the electrolyte in the cells. Would just like to be able to hit it harder at the start to break up any sulfation. So I'd be satisfied with 60 amp. The 3ph charger is 100amp. I was looking at the solar mppt controllers mainly because the programmed logic in them is specific to very large battery banks. The mppt chargers also cap the amperage so if I fed it with a switched power supply that that had appropriate wattage then they wouldn't trip over current when the controller requested all of what it can do.

 

Also to help with sulfation I added Epsom salt to distilled water when I topped the cells off. I found an interesting article on reconditioning forklift batteries that gave specific amounts of epsom salt to add.