480VAC SINGLE Phase Motor

[TimWilborne]

Any thoughts on where I can get a 1/2 hp 480 VAC Single Phase motor with a 56C frame? Thanks TW

[Leitmotif]

I have never seen one but am sure someone makes one. Seems like an unique situation. Think it would be easier and cheaper to use 3 phase 1/2 HP. 480V implies to me you have 3 phase. Dan Bentler

[TimWilborne]

You know I always thought 480V implied 3 phase too, but apparently not always. It's single phase. I decided to go with a 1.5KVA 480 x 230 VAC transformer and run it off of 230VAC single phase

[HiGhVoLtAgEgUrU]

extactly what I would do. But I never seen 480V single phase motor? I thought 480V 3 phase. What is your application for this that you need a 480V single phase motor

[TimWilborne]

480VAC single phase is the only available power at this location. Pretty much the site is on top of a mountain with a single 7200 volt line going to it and a single 480 VAC transformer on the pole. I am running a 60 hp 3 phase motor on a 125 hp motor and a 7.5 3 phase motor on a 15 hp drive both connected to single phase at the site. They need to add another motor fast so I just thought I could connect the motor to a contactor if I could get a 480VAC single phase motor. I did find that you can get them, but they are special order. Can't deal with the lead time plus I hate to put a odd product in a system.

[Leitmotif]

Another way to do the 1/2 HP motor is with a 1/2 HP rated VFD single phase - not sure if you can get those on 480 single phase - you could use a 1 HP 480 3 phase VFD to allow for single phase derating. I take it you are using a rotary converter (125 HP motor) to derive 3 phase to drive 60 HP motor. No matter how you look at it - an interesting and uncommon situation. Dan Bentler

[TimWilborne]

Then you throw the fact that it is on an underpowered line about 20 miles off the grid with harmonic distortion problems and it's not as easy as just adding a drive Like I said we are already running a 60hp and a 7.5 hp motor on a 125hp and a 15hp drive powered single phase. While undocumented on most drives you can typically double the hp of a drive and run a motor off of single phase drive. After much research I found out that phase converters aren't a great idea. Here is an article from Hitachi on doing this http://www.automation4less.com/pdfs/AN0324...ingle-Phase.pdf But in order to keep the power company from screaming we were required to put harmonic filtering equipment on the drives to keep the distortion down. This isn't something you can get off the shelf really quick for single phase applications. In the end we would be looking at thousands of dollar$ and 4 to 6 weeks to add a simple 1/2 hp drive. Hence my original question about the single phase motor. Best I can tell the 480 to 230 VAC transformer was still the best option to be ready to go Tuesday. Let's hope everything works! Do you think I should put the motor starter before or after the transformer? I'm think after. Thanks TW

[Duffanator]

Yeah, I would put it after the transformer too. In a real pinch (if you didn't have such a transformer) you could probably wire a 240 single phase motor from one leg of 480 to ground (depending on your source power that is...) and run it off of 277 Volts. It would probably last you a few days until you got something in to replace it.

[Leitmotif]

Ah the plot thickens now you got the utility and their problems with harmonics whether real or not they will be all over you about them with a VFD. Kinda surprised with this much motor load they are not squaking over power factor. Then there is 20 miles of rough road to get there. For sure you want to go as off shelf as possible and ensure no callbacks. Given all that stuff the 480/230 transformer and a 230 single phase sounds easiest and long term most cost effective. You could put the starter on the xfmr hi side you would save by reducing motor corrent by half - but that is added expense due to 480 and considering current draw when energize transformer. Especially in this setup I would go with starter on lo side of xfmr. Just for curiosity what is this installation - military or phone company stuff? Dan Bentler

[TimWilborne]

Sorry Dan, I thought I replied to this one. It's natural gas

[bowhunter2000]

TW I found this on yahoo http://phaseable.com/ hope this help you

[Leitmotif]

aaah that explains large motor - could not figure why phone company would need such large motor. Did you get it working? Dan Bentler

[TimWilborne]

Look like it, just got it installed yesterday evening

[Leitmotif]

Sigh a bit late but it has occurred to me what are they using for lighing and did they put in 120/240 for receptacles? If not and if transformer is tapped you could use it for receptacles assuming a little room capacity wise. Dan Bentler

[milldrone]

TW, This is just for general info use (not for your project). Single phase 480 volt motors are common in the HVAC industry. The problem though is that they are all stud mount (no base) and wierd shaft configurations (5/8 shaft with a flat insted of a keyway). They use these for condenser fans on 480volt three phase refrigeration systems. I have no idea why they use a single phse motor for the fan.