[WesM]

Craig,

For reliability we don't design to nominal voltages, we design to worst case, as stated the utility specified tolerance is 240V + 6% , resulting in 360Vdc, These drives have a 350V bulk capacitor. I completely agree 600V FET's are common as nails so are 400V capacitors. In all likelihood the Delta drivers have 600V FET's and 400V capacitors, IIRC the S.O. drives have a 350V capacitor! Furthermore the mains voltage in New Zealand is nominal 230V.

Just to be clear, the stepperonline T6 drives do have 400v caps. I can see two large caps with 400v 560uF marked on them. There are also some smaller CD28S caps I can see. My concern would be that there are other electronics in the drive that might not be able to handle higher then the 242v they are rated for.

So I guess my question from all of this is, besides cost, is there a reason NOT to use a transformer to bring voltage into the manufacturer recommended range? Seems like using a transformer cannot hurt.

I live in NA and have seen voltages at my house as high as 249VAC, typically in the afternoon its around 243VAC.

[joeavaerage]

Hi,

So I guess my question from all of this is, besides cost, is there a reason NOT to use a transformer to bring voltage into the manufacturer recommended range? Seems like using a transformer cannot hurt.

No, there is no penalty that I'm aware of, excepting cost. The transformer would need to be very large to accommodate all those servos would it not?

I suppose its a matter of style. For instance I use a line reactor on my VFD where most people don't bother. You use a transformer where I would not bother.

Craig

[slow-poke]

Just to be clear, the stepperonline T6 drives do have 400v caps. I can see two large caps with 400v 560uF marked on them. There are also some smaller CD28S caps I can see. My concern would be that there are other electronics in the drive that might not be able to handle higher then the 242v they are rated for.

So I guess my question from all of this is, besides cost, is there a reason NOT to use a transformer to bring voltage into the manufacturer recommended range? Seems like using a transformer cannot hurt.

I live in NA and have seen voltages at my house as high as 249VAC, typically in the afternoon its around 243VAC.

The drive has a factory set upper limit alarm (that shuts the drive down) at 242V.

[slow-poke]

A transformer in buck mode can actually be reasonably small because the vast majority of the current only flows in one 20V secondary winding. The $20 transformer (visible in the control box image below) is good for 30A@220V, I don't anticipate more than two servos operating at any given time, so this transformer is actually overkill for my application but it was the smallest 240:20V transformer at hand. I also have a much larger toroid, however besides the fact that it was grossly overkill it would pop a 30A mains breaker way before it would be at a fraction of its output at 220V

[WesM]

Hi,

No, there is no penalty that I'm aware of, excepting cost. The transformer would need to be very large to accommodate all those servos would it not?

I suppose its a matter of style. For instance I use a line reactor on my VFD where most people don't bother. You use a transformer where I would not bother.

Craig

Buck transformers are pretty cheap. I was able to get a used one thats rated for 50a @ 240v for about $50. It will take my 245vac down to about 222vac. New they are around $150.

Just to be clear, I do see this as a disadvantage to these particular servos/drives. But even with the cost of a buck transformer at retail of $150 and the cost of the servos at $206 each with a total of $750 for three + the transfromer, they are still significantly cheaper then a set of 3 750w DMM tech servos (about $2300) or a set of delta servos ($1500). What I wanted to find out was how they compared in use.

The drive has a factory set upper limit alarm (that shuts the drive down) at 242V.

Ah ok, I did not realize there was a hard limit baked in. Good to know. I guess that answers the question of if you need a transformer or not! Well, at least if your power source is delivering over 242v.

[joeavaerage]

Hi,
Delta B2 spec specify for single phase input 200VAC to 255VAC +- 5%. I'm well in that range.

Craig

[WesM]

The drive has a factory set upper limit alarm (that shuts the drive down) at 242V.

Did you end up using the 5v differential signaling or the 24v single ended?

[joeavaerage]

Hi,
my plan was to use single ended signaling (24VDC open collector). Delta specify 200kHz max. I thought that I might try higher than that as often the reality is higher than the spec.
Signaling was reliable at 200kHz, started to look a little flaky at 230kHz and was just plain missing steps at 250kHz.

As my machine requires that I signal at 416.66kHz (at max servo speed and my preferred resolution) I perforce used differential signaling.

The industry standard line drive IC is the 26LS31, which is 5V input, 5V output. I decided instead to use AEIC7272's. They are both 3V and 5V input tolerant and have a separate output supply so you can tailor
the output swing to match your application. I chose a 7V output supply which results in a full 5V output swing. It also has very good output overload protection. I have run them up to 800kHz and they are 'as smooth as a babies bum'.
They are a little more expensive ($12NZD each cf $2.75NZD each for 26LS31) than I'm used to paying, but for the smooth signaling I'm happy with them.

Attached is the pic of my own breakout board.

Craig