Converting 250V 3phase to 208V 3 phase

[tbob]

I need your help! I sell restaurant equipment at work. I have a customer who wants to buy a used 208V 3phase chicken pressure fryer from us. When you measure across two of the three phases she has in her place you get a reading of 252 Volts. If we hook up the unit "as is" it will eventualy burn up the elements.
As I see it we have two options:

1. 1. Find her a another 240V unit
   2. Find a transformer to "step" down the power from 240 to 208

Do they make such an animal?
Thanks, Terry
P.S. It draws about 41 amps on each leg

 

[hidollartoys]

You should check with the power co to determine exactly what voltage they are supplying. If it actually 240v then check with the equipment mfg'r to see if that particular fryer can operate on 240v. If the supply voltage is 240v and the equipment requires only 208v then you can install a stepdown transformer. Since you are in KC you should check with Industrial Surplus @816-920-7077. NO I dont worl there or have ANY connection, Just know they exist.

 

[Stuart in MN]

Yes, a 240:208 stepdown transformer is a common item. Any local electrical supply house should be able to get you one. Also, check to see if the fryer is rated for use at either voltage and/or can be rewired for 208 before you go further, many devices have that capability. It should be marked on the nameplate on the back, or contact the manufacturer (you may be able to go to their website and find specifications and installation instructions.)

 

[tbob]

Thanks for the input guys. Power was checked by electrician. It's going to Hiawatha, Ks, which is about 1.5 hours away from KC. We try to cut down on service calls by getting it right the first time. The unit is specific for 208. I'll see if I can get a transformer here in KC. Is this called a KVa?

Thanks again, Terry

 

[hidollartoys]

KVA is the capacity rating for transformers. Your application will require a 10 KVA transformer. KVA is "Kilovolt ampere" For 41 amps @208 volts ...... 208 x 41/1000 = 8.52 KVA. Supply the amp draw and the voltage to your transformer supplier and they will size the transformer accordingly.

 

[W-Cummins]

You need to use buck/boost transformers (an autotransformer) in the buck mode. They are made for just this application and are cost effective.

William...

 

[Torque1st]

Again, check with the local utility company for the service specs at the intended location. It looks like the electrician is measuring the "wild leg" which can vary with loading. Get your information correct before you spend $$ on a transformer and multiple service calls to get the job done right.

 

[W-Cummins]

When you measure across two of the three phases she has in her place you get a reading of 252 Volts.

Sounds like a Normal 240V service to me ( it's a little hot but within 5%) My 480 service is also slightly hot at 498-500v. I think the local guys run it hot here to allow for a heavy load pulling it down at times of high demand...

Again, check with the local utility company for the service specs at the intended location. It looks like the electrician is measuring the "wild leg" which can vary with loading.

No, it dose not look like a wild leg measurement at all, he said it was measured between the hots, The wild leg "measurement" is from a hot, to the grounded conductor if present, or the equipment ground if not ( in the case of no grounded conductor the wild leg is not a problem as you are not to use the equipment ground as a return path.

William....

 

[nadogail]

I have successfully used Buck Boost transformers is situations like this. Both to boost up or buck down, as needed.

 

[Norcal]

With 240V 3Ø any phase to phase measurement between the high leg & any other phase will be a nominal 240V. Buck/Boost transformers are what is needed to operate 208V equipment on 240V.

 

[Terry D]

This is almost a 13 year old thread

 

[wyliesdiesels]

I need your help! I sell restaurant equipment at work. I have a customer who wants to buy a used 208V 3phase chicken pressure fryer from us. When you measure across two of the three phases she has in her place you get a reading of 252 Volts. If we hook up the unit "as is" it will eventually burn up the elements.
As I see it we have two options:

1. Find her a another 240V unit
2. Find a transformer to "step" down the power from 240 to 208

Do they make such an animal?
Thanks, Terry
P.S. It draws about 41 amps on each leg

you need either a stepdown transformer(auto transformer) or a bank of 2 transformers wired to buck (reduce) the voltage.

if you go the bank route, you will need a pair of 1.5KVA 240x120/32x16v transformers. The cost for these might be about the same as a single auto transformer

You should check with the power co to determine exactly what voltage they are supplying. If it actually 240v then check with the equipment mfg'r to see if that particular fryer can operate on 240v. If the supply voltage is 240v and the equipment requires only 208v then you can install a stepdown transformer. Since you are in KC you should check with Industrial Surplus @816-920-7077. NO I dont worl there or have ANY connection, Just know they exist.

no need... its 240D/120 3Ø running a little hot

KVA is the capacity rating for transformers. Your application will require a 10 KVA transformer. KVA is "Kilovolt ampere" For 41 amps @208 volts ...... 208 x 41/1000 = 8.52 KVA. Supply the amp draw and the voltage to your transformer supplier and they will size the transformer accordingly.

that's the equation for single phase.

3 phase you need to multiply by 1.732- 1.732x208x41/1000

KVA needed is ~15

Again, check with the local utility company for the service specs at the intended location. It looks like the electrician is measuring the "wild leg" which can vary with loading. Get your information correct before you spend $$ on a transformer and multiple service calls to get the job done right.

no need to do so. there is only 1 service that runs at 240v- 240 Delta. The measurement of the wild leg also doesnt matter here and would be ~208v phase to neutral or ground. Since the measurement is 252v, they arent measuring wild leg to grounded conductor. Again, the wild leg is inconsequential here.

 

[alfredeneuman]

Federal Pacific has a calculator for buck/boost transformers here.
https://www.federalpacific.com/tools/buck-boost-transformer-calculator-selector/
(Unlike their breakers their transformers are top-notch)

 

[MBfreak]

You may be lucky and find a 3 phase step down transformer to 200 V used for typical Japanese numerically controlled lathes, mills etc.
In the 1970/80 s they were usually rated at 3 phase 200 V, which I GUESS was the prevalent voltage in Japan.
As machine shops upgrade I have seen tons of 380/200 V 3 phase 15 kVA transformers here in Sweden being sold for scrap.

You may find similar units in the US, check with a reputable supplier of modern numerically controlled machines.

Ola

 

[alfredeneuman]

In the 1970/80 s they were usually rated at 3 phase 200 V, which I GUESS was the prevalent voltage in Japan.

A standard voltage in Japan is 100/200V
As far as in the rest of the World 200V equipment is designed to run on 208V systems, just as 230 and 460V motors are designed to run on 240 and 480V systems respectively. 380V equipment is built for a 400V (European) system

 

[DeeKay]

Hopefully the OP got this figured out within the last 13 years.....

 

[Norcal]

Since the software change we have had even more old threads then normal unearthed from the graveyard.