What's new
What's new

480V Transformer for 10" Baldor Grinder

Trevlaw

Aluminum
Joined
Dec 14, 2019
I recently won an auction lot for three Baldor grinders. Originally thought they were 8" based on the auction pictures, but turns out two of them are 1.5hp 3 phase 10" grinders. All three are three phase, the 8" and one 10" are 240/480 dual voltage, but unfortunately the other 10" is only 480v. I have a feeling they are all wired for 480, but changing the leads on the other two is something I think I can figure out myself.

I've got about $300 total into this lot of grinders, a pretty good deal in my area and all of the cast iron guards are in perfect shape. I'd really like to be able to use the odd 10" 480v, but I am a bit of an electrical delinquent and reading about transformers for the last couple days has left my fairly confused.

From what I've read it seems that a 480v primary/240 secondary transformer, dry type I think, should be alright to wire backwards to step up my 240v 3 phase power coming from my 10hp RPC. The name plate on the grinder listed an amp draw of 1.3, so I think that would mean a 1 KVA or larger transformer would be alright to use?

My confusion starts around different transformers being Delta-Delta or WYE, as I have no idea what that means. I dropped the grinder off at my local motor shop to have it surge tested to see if its good or not. The guy at the motor shop seemed to explain that I would need a true Step Up transformer to run this, $$$, as he was trying to explain that wiring a step down transformer backwards would not give me the full power out of the grinder, along with something about grinders having a high amp draw at start up.

I am contemplating just selling the grinder if it tests good, to recoup my auction price, make some money on top and avoid dealing with all of this. Though the idea of having 480v available is enticing as I do have a habit of acquiring machinery and there have been a few cheap 480v 12" grinders I've passed on that would be nice to have if I could use a single transformer for multiple machines, though probably not at the same time.

I've attached a picture of a local transformer for sale near me that caught my eye, it seems that 3 phase transformers aren't nearly as common as single phase, and I believe the 3 KVA means I could possibly power a larger hp motor off of it. I've seen mention of using multiple machines with one transformer requiring a branch circuit, and a branch circuit being more complicated than wiring to one machine? For my uses having a transformer with a 240v input plug and a 480v output plug would be adequate, the idea being I'd just unplug one machine from the output and plug in another to use, if that would be possible.

I'm obviously out of my element here, but I like to learn new things.

Any and all help is greatly appreciated, Thanks.
 

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
I bought a NEW Acme years ago - Acme specified 3 KVA for 1 1/2 HP

Acme referred to them as General Purpose Three Phase Dry Type

They had no issues at all about wiring them up "backwards" as needed

Zero issues in 18 years
 

30yearoldjunk

Plastic
Joined
Sep 27, 2017
From the Acme Electric catalog:
7. Can Acme Transformers be reverse connected?
ACME dry-type distribution transformers can be reverse
connected without a loss of kVA rating, but there are
certain limitations. Transformers rated 1 kVA and larger
single phase, 3 kVA and larger three phase can be reverse
connected without any adverse effects or loss in kVA
capacity. The reason for this limitation in kVA size is, the
turns ratio is the same as the voltage ratio. Example: A
transformer with a 480 volt input, 240 volt output— can
have the output connected to a 240 volt source and thereby
become the primary or input to the transformer, then the
original 480 volt primary winding will become the output
or 480 volt secondary. On transformers rated below 1 kVA
single phase, there is a turns ratio compensation on the
low voltage winding. This means the low voltage winding
has a greater voltage than the nameplate voltage indicates
at no load. For example, a small single phase transformer
having a nameplate voltage of 480 volts primary and 240
volts secondary, would actually have a no load voltage
of approximately 250 volts, and a full load voltage of 240
volts. If the 240 volt winding were connected to a 240 volt
source, then the output voltage would consequently be
approximately 460 volts at no load and approximately
442 volts at full load. As the kVA becomes smaller, the
compensation is greater— resulting in lower output voltages.
When one attempts to use these transformers in reverse, the
transformer will not be harmed; however, the output voltage
will be lower than is indicated by the nameplate.
 

Strostkovy

Stainless
Joined
Oct 29, 2017
I bought a NEW Acme years ago - Acme specified 3 KVA for 1 1/2 HP

Acme referred to them as General Purpose Three Phase Dry Type

They had no issues at all about wiring them up "backwards" as needed

Zero issues in 18 years

I have the same setup on a computer controlled hydraulic press. No issues.
 

Trevlaw

Aluminum
Joined
Dec 14, 2019
Ok, good to hear that several of you have used a reverse wiring setup with no issues, sounds like it would be a viable solution to my situation.

I see I forgot to attach the picture, here is the transformer for sale locally, it is a 3kva, but not an acme brand. Any idea if other manufacturers would be just as capable, assuming this is the dry generic type of transformer?
61b3b5f1623eeceadd6a20440b628a2c.jpg


Sent from my moto g(7) using Tapatalk
 

Trevlaw

Aluminum
Joined
Dec 14, 2019
Would be curious about the 480 motor: how many leads are in the connection box going into the motor?
Not sure, I didn't really dig into it before dropping it off at the motor shop to get it surge tested. Maybe he will find something during the test, if not I can dig into it when I get it back. He did mention he thought it was odd that it would be just 480v. The other 10" that came in the auction lot is the same exact grinder, and same 1021w model number I believe, but the tag states 240/480 on the other one.

Seems like that picture quality might be pretty bad, I may need to repost it on my PC, as I'm not a Tapatalk VIP...

Sent from my moto g(7) using Tapatalk
 

Strostkovy

Stainless
Joined
Oct 29, 2017
I can't read the nameplate but I'm using the 208 wye winding as the primary and 480 delta winding as the secondary. It's not exactly how it's supposed to be done but works fine.
 








 
Top