1200mmX900mmX170mm 4axis cnc

[Nickhofen]

In my case it would be good to get back to where I started - spent the afternoon reassembling my lathe and getting the safety switches operating reliably. Then reinstalled the VFD (when I took it out months ago to fix the broken mounting lugs, I photographed the connections and labelled them as I disconnected each one). Now I am getting a code that says low DC bus. I sense a new thread coming if I can't sort it easily.

What your multi meter says, did you take any measurements?

[cropwell]

What your multi meter says, did you take any measurements?

No Sir, It was working fine as a VFD before I took it out. My next step is to double check the connections, but not today, I have had enough. I will start fresh tomorrow, but tonight is beer, roast chicken and relax.
This will be a new thread I'll bet. I don't want to hijack yours !!!

[Doddy]

Finish the power supply, thanks everyone for the help.

Neat layout.

Minor observation:-

It can be a good idea to wire a bleed resistor across the output - nothing too big, but enough that you're not holding a substantial and dangerous charge long after removing the power.

Also, there's some concern with the use of screw terminals particularly with high-current circuits and when vibration may be present that the screws can loosen over time.

[Nickhofen]

No Sir, It was working fine as a VFD before I took it out. My next step is to double check the connections, but not today, I have had enough. I will start fresh tomorrow, but tonight is beer, roast chicken and relax.
This will be a new thread I'll bet. I don't want to hijack yours !!!

Do not worry about hijacking this thread,just bring the chicken and beers, I will buy some souvlakia with tzatziki also,lol!

[Nickhofen]

Neat layout.

Minor observation:-

It can be a good idea to wire a bleed resistor across the output - nothing too big, but enough that you're not holding a substantial and dangerous charge long after removing the power.

Also, there's some concern with the use of screw terminals particularly with high-current circuits and when vibration may be present that the screws can loosen over time.

Thanks for the observation ,can you point me a value for the resistance and how many watt it should be? I have some laying around here at home.I will change the terminas as soon as the other ones come with the mail.

[Doddy]

Thanks for the observation ,can you point me a value for the resistance and how many watt it should be? I have some laying around here at home.I will change the terminas as soon as the other ones come with the mail.

Value?, pick a number. I recently ordered 1500 Ohm, 7W wirewound resistors for an 80V supply. Just remember Ohm's law - you can determine the power rating from the voltage and chosen resistor value (P = V*V/R) - the lower the value the quicker it will discharge, but the beefier the resistor needs to be, and the more energy you throw away.

[Nickhofen]

That's super tidy, I see you went DC in the end. What voltage output transformer is it? 50v?

I wired the transformer to a 13 amp light style switch and then my VFD and water pump to another switch and both of them are wired from the emergency stop.

This way I can easily turn the transformer on/off and if the vfd is powered the water pump is on. I have both switches and the emergency stop at the front of the machine for easy access in a row.

If I hit the emergency stop it kills power to both the steppers and the vfd, I still have to work out how to get it to trigger an estop on the pc but it's good enough for me at the moment.

I went DC because I have two AM 882 and waiting for other two AM882h to come,so DC was one way road....

[m_c]

Brill

It is good practise to not to daisy chain the 70V across each drive ie. use separate power leads from each drive to a common block and then connect the PS to the block. This ensures you are not getting a volt drop to each drive from the first one.

I'm going to engage pedant mode for a moment.
It's not to do with volt drop, it's mostly to do with the risk of harmonics.
Stepper drivers are essentially a complex switched mode power supply, which means they don't draw a constant current, they're constantly switching at high speed. If you place multiple of these on the same wire, then you risk harmonics, which is where multiple spikes at the same time lead to high voltage spikes, which can destroy electronics very quickly, and in extreme cases will burn out the wiring, even though the total current may be well within the current limit of the wiring.

Off course the latest drivers are far more likely to contain some internal filtering to help avoid noise being propagated into the supply, as part of them meeting various approvals, which should avoid any harmonic problems.

Avoiding daisy chaining also helps minimise any potential damage from a failed connection, as a connection failure during deceleration is very likely to result in an overvoltage failure, with resultant smoke release from drives. By having them wired direct, the worst case is one drive fails, but if daisy chained, you risk every drive after the bad connection failing.


Personally, I always wire drives directly to the main smoothing capacitor, as it avoids having any more connections in the wiring than needed.

[cropwell]

Do not worry about hijacking this thread,just bring the chicken and beers, I will buy some souvlakia with tzatziki also,lol!

Trad English Roast Chicken, Stuffing, Roast potatoes, parsnips and braised carrots, None of this forrin stuff

If you use a 5k bleed resistor, you will not have enough current going through it to significantly affect the PSU in operation and a 2W resistor should handle the current. I don't know what capacitor value you have but 5K will bleed down fast enough.

[Neale]

A bleed resistor might be useful while you are testing, but once you have a driver or two wired to the power supply, they look like a waste of time. When I checked my machine, the stepper driver power supply was down to a few volts within seconds of cutting power. Any resistor that drains down faster than that is going to need to be a fairly high wattage item, and is going to produce more heat than you probably want in the control box.