480 3 ph vs 208 3ph

[RPosty]

I work on industrial equipment most of which can be wired for either. What are the Pro's and Con's of each? Also I noticed that one of our systems has the Transformer that converts 480 to 208 right next to the Transformer as opposed to near the equipment 100' away. wouldn't it be easier to run the lighter gauge wire from 480 panel to the equipment as opposed to running the heavier gauge? Is there a reason the Transformer has to be right at the Panel?

"I am stuck on Band-Aid brand, 'cause they are stuck on me"

 

[waross]

I agree with your observations.
Most three phase motors are suitable for 230/460 Volt operation (from a 240 Volt or 480 Volt supply.
200-230/460 Volt motor are not as plentiful and may cost a little more.
That reminds me of my time "South of the Border" in Central America.
Electricians got an under the table kick-back on transformer purchases. For large purchases of building wire a kick back could be negotiated.
One plant with a lot of refrigeration had both 208 Volts and 480 Volts available. Every 208 Volt motor was fed by transformer from the 480 Volt supply and every 480 Volt motor was fed by transformer from the 208 Volt supply.
I made excuses that I was not competent to work on their equipment and left to find work with other plants.
I would advise keeping your observations to yourself.
Someone in management may be in on the scheme.
Asking valid questions may create an embarrassment that could be abated by your departure.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[wayne440]

...Asking valid questions may create an embarrassment that could be abated by your departure.

That is a very well put observation, do you mind if I plagiarize it on rare occasion?

 

[waross]

Sure Wayne. Feel free. I'll bet you have "been there, done that" once or twice as well. Grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

... Also I noticed that one of our systems has the Transformer that converts 480 to 208 right next to the Transformer as opposed to near the equipment 100' away. ...

Something about that sentence has me thrown off. Did you mean perhaps that the transformer is near the 480V panel, as opposed to being nearer to the machine? One possible reason for that might be environmental: the area around the machinery is too: <insert adjective here> crowded, oily, dirty, hot, cool (don't want the transformer heat), quiet (can't have the hum of the transformer), etc. etc. That's not so uncommon.

As to the why 208 vs 480V? Generally, 208V is good for commercial and "light industrial" (loosely defined) installations where the preponderance of loads is lights, power outlets for small single phase equipment, plus maybe a few 3 phase machines or HVAC equipment and distances from the service entrance to the loads is relatively short (relative to a large industrial plant).

As to why use 208V IN a large industrial plant? Typically for outlets and single phase loads WITHIN the plant, because in a 208V Wye system, you get 120V phase to neutral and 208Y120V transformers are easy to feed from the larger 480V system while still keeping the load balanced as much as possible.

As to why YOUR system is using 208V for what is apparently a single machine when you obviously have 480V available, most likely because that specific machine will not run on 480V. It happens, especially when people move machinery from somewhere else or buy used machinery. Otherwise it does not make economic sense. All transformers have losses associated with them, mostly based on the current they handle. That's why 480V makes more sense for industrials with lost of larger motors. In this case, going with 208V, if there were an option, would make the energy costs for that machine significantly higher over time.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[waross]

Is this 480:208 Volt transformer dedicated to the machine or is it a lighting panel?
How large is the machine? HP, KW?

Bill
--------------------
"Why not the best?"
Jimmy Carter