We have a new machine shop that is going to be installed at our school. The equipment is rated 230 volt 3 phase. What we have available is 208 volt 3 phase. The machines have a control transformer in them that steps the voltage down from 230 to 24 volts. My question is if they are supplied from 208 volts will the control voltage be to low for the controls? I am calculating it to be around 21.7 volts.
Machine Shop
- Thread starter CONDUIT
- Start date
- Status
- Location
- Massachusetts
You might find the control trans has taps for 208 or 230.
There isn"t any taps for 208 volts!
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Maybe contact equipment manufacturer and see what they have to say.
Many cases they will work just fine.
Warranties could be voided though if not connected to rated voltage.
Worst case you will need to install a transformer to supply this.
Does equipment instructions give you an acceptable voltage range? If it has say 10% tolerance from 230 (207-253) volts you likely still fall within equipment tolerance. If your 208 input is on the high side (here it will often be about 215) that helps.
Many cases they will work just fine.
Warranties could be voided though if not connected to rated voltage.
Worst case you will need to install a transformer to supply this.
Does equipment instructions give you an acceptable voltage range? If it has say 10% tolerance from 230 (207-253) volts you likely still fall within equipment tolerance. If your 208 input is on the high side (here it will often be about 215) that helps.
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Typical
Typical
It seems to be typical that bureacratic institutions always buy equipment without checking with Engineering on anything.
The HVAC world adapted to 208-230 by pretty much making all gear rated down to 208 with 208V control transformer taps as noted above.
I would go straight to the OEM and ask them about the supply voltage vs. whats been provided.
AS an example, Ingersol Rand Air compressors must be ordered with 208 or 230V motor specified. If you connect a 230v rated motor to 208v supply in their case the warranty is void.
Typical
It seems to be typical that bureacratic institutions always buy equipment without checking with Engineering on anything.
The HVAC world adapted to 208-230 by pretty much making all gear rated down to 208 with 208V control transformer taps as noted above.
I would go straight to the OEM and ask them about the supply voltage vs. whats been provided.
AS an example, Ingersol Rand Air compressors must be ordered with 208 or 230V motor specified. If you connect a 230v rated motor to 208v supply in their case the warranty is void.
- Location
- Massachusetts
Seeing as school shops often have EPO buttons the easiest thing to do might be to set a new panel exclusively for all the 230 loads, buck boost that one panel and equip it with a shunt trip main breaker.
We have this exact setup except it is 208 volt's!
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
I'd like to know who's making US equipment for 230v 3 phase. Seems odd to me.
(Oh, and please stop with the !, a period will work. thanks.)
(Oh, and please stop with the !, a period will work. thanks.)
- Location
- Massachusetts
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Except buck boost is not a good option unless you have a reasonably constant load. This is good for a single fixed amperage piece of equipment, but not for variable loads, or a machine shop where the total draw could fluctuate greatly. An isolation transformer would be the right way to treat this situation.
- Location
- Massachusetts
A buck boost is fine for varible loads unless you are trying to boost to overcome voltage drop caused by undersized supply conductors.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
130910-1558 EDT
Strathead:
A buck-boost transformer with a comparable source impedance to an isolation transformer provides a lower cost, lower weight, and greater efficiency solution than the isolation transformer.
.
Strathead:
A buck-boost transformer with a comparable source impedance to an isolation transformer provides a lower cost, lower weight, and greater efficiency solution than the isolation transformer.
.
zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
Right, of course. :slaphead:
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Yeah, as soon as I read what you wrote the light went off. I knew of a problem, but forgot to think it through.
ATSman
ATSman
- Location
- San Francisco Bay Area
- Occupation
- Electrical Engineer/ Electrical Testing & Controls
The power supplies we use for our automatic transfer switches in that range are dual rated: 240/ 208V. Plus this falls under the 10% voltage rule so I do not see a problem but verify it with the manufacturer as others have mentioned because of warranty issues.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Most general purpose motors are rated 230/460 volts, with 208 being optional at a higher current.
If you have something with say a three phase heating element- the rating that is usually mentioned is the 240 volt rating, and if it is marked with a 208 rating it is kind of a "by the way" type of rating.
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