looking for alternative toroidal autotransformer for Aerotech Amp

[yantra3d]

Hey guys, I hope you can help me out with this! I have an Aerotech (BA30) Amp that I want to use with an Aerotech DC1000 servo motor that requires 40VDC bus. The amp runs at 320VDC so the manual recommends using the Aerotech TVO.3-28 autotransformer to acheive the lower bus.

I contacted Aerotech to see what the cost is for this item they want $215 for it! Now, I'm not very knowledgeable when it comes to electronics but something tells me that I can do better than this so I was hoping you guys could steer me in the right direction for a more cost-effective alternative.

Here are the specs for the recommended transformer:

model: TV0.3-28
-0.3 kVA isolation transformer for 40 VDC bus
-100,115,200,230 VAC input 50/60 Hz.
-Dual secondary windings (28 VAC @ 5A RMS) each
-Integral thermal switch

Here's a link to the manual for the Amp I have (It's the BA30 model) if it helps:

BA10_20_30.pdf

Any help on this would be greatly appreciated...

Thanks!!

[Al_The_Man]

There is a guy on ebay that Makes/sells toroids of various outputs.
Al.

[yantra3d]

Hey Al, thanks for responding... I was hoping you might be one to help out on this.

I have looked at the ones on ebay and the closest one I could find is this one:

16-16V-300VA-Toroid-Transformer-CNC-Motor-Driver

But, it looks like 16 VAC instead of 28 VAC. Could I somehow make either this one or another one work for me? Unwinding, etc...? Sorry if this is a basic question... still have a lot to learn obviously.

Thanks again!

[Al_The_Man]

You could add windings, but it might be worth an email to him and ask if he has closer to the size you want, alternatively he puts up all sizes at times so I assume he is capable of making one up for you possibly.
Also, you can put the windings in series for 2x16 and if too high, just take a few turns off. As long as the VA size is OK for your use.
Al.

[yantra3d]

Thanks a lot for all the info... I really appreciate that! I emailed him to see if he has any that are a closer match.

I did a little more searching and found this one here:

300VA 240/2*28v @5.3A

Do you think this one would work for me? What about the 5.3A rating though... Can I step that down to 5A or will the extra amperage harm the drive, etc....?

Thanks again!

[Al_The_Man]

You realize that one is 'Down Under', may take a whack of postage.
You only draw the current demanded by the drive/load etc, so it's OK if higher current rating.
Al.

[yantra3d]

Ok, thanks for clarifying that for me. So, does this rule also apply to the VDC then? Does the Aerotech transformer then create a total of 56VDC (2x28V) and it's the drive/load that draws the 40VDC that it requires? Am I understanding that correctly?

[Al_The_Man]

No, the drive requires a supply of 40vdc which must be supplied by you ( and the DC supply). The current (amps) drawn from the supply will be dependant on the load demand. IOW when the motor is at idle, the supply will still be 40vdc but the current may be just an amp or so, depending on the function it performs. The supply must be capable of supplying the current demanded by the motor when the load demands it.
Ideally the voltage will be a constant 40vdc.
Al.

[yantra3d]

Ok, I see. This is starting to make more sense I think. I'll try to research this a little more and see if I can get my head wrapped around it so I don't have to bother you with all these little questions. This is all new to me and so you're help is really appreciated.

Thanks again!!

[yantra3d]

I'm confused about the output amps. It appears as though the amp rating is somehow dependant on the "voltage drop" that takes place - like it gets multiplied in relation to the voltage being stepped down. So, this leads me to think that I would end up with a larger amp rating if I stepped 320v down to say 40v compared to stepping 110v down to 40v.

How does this work... would the amp output or RMS remain constant - regardless of the input voltage? Can you explain this to me?

[Al_The_Man]

I think you are refering to the VA Volt/amp rating of the transformer, which remains constant whatever transformation takes place, in other words if you have a transformer rated at 500va, and have a 50v 10a winding (500va), If you decrease the winding to 25v then providing the wire dia. is large enough, you can draw 20amps from the supply (25x20=500va).
Al.

[yantra3d]

I just read over the manual again and found a couple of important bits of information. Apparently the BA amp rectifies the 28VAC to 40VDC so that fills in the missing piece of the puzzle there. However, it also says that the transformer is available ONLY for the BA10 and BA20 models and since there are only 3 models in the BA series -mine being the BA30 model - then this likely means that I've hit a brick wall.

I think this is pretty much the end of the road beccause both the BA10 and BA20 have a DC bus voltage range of 80-100v, 80-160v, 80-320v but the BA30 only has a range of 160v, 160-320v.

Being the electrical genius I obviously am, I put two-'n-two together and figured out why they state that the transformer only works for other two models. Time for next lesson.

Thanks again for all your help Al... I really appreciate it!!