kwired
Electron manager
- Location
- NE Nebraska
Around here the no load voltage of 208 volt systems is usually going to be right about 215 that is only about 2.3% from the motor 220 rating in the OP.
220V motor on 208V?
- Thread starter olc
- Start date
- Status
That's fine. But usually one would design for operation within the supply tolerance limits. What if your nominal 208V was just at the lower permissible limit?
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
olc -
I haven't seen a new, 220V, 60Hz motor for over 40 years - maybe longer. Is this a 50Hz motor per chance? With two motors, 2hp and 3/4hp, this sounds like an offshore machine, and the nameplate says 50hz.
If it is a 1960s vintage, U-frame, 220V, 60hz, I'd run it at 208V, 60hz. Put in new bearings, check the balance, it will be fine, likely for ever.
ice
Unless it is very old, a 50Hz motor would be rated in kW rather than HP.
kwired
Electron manager
- Location
- NE Nebraska
That would deserve higher consideration for me if I worked a larger area then I typically do. The rural systems around here always run right about the level I mentioned that is unloaded, put load on them and they still typically are above nominal voltage level. If not it is usually voltage drop on user side of service or POCO has a problem and is not a permanent condition.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Maders
Member
- Location
- Boston, MA
NEMA MG-1 specifically recommends against this.
This standard specifies that motor nameplate voltages shall be lower than the nominal system voltage to which they are applied. This takes into account voltage drop from the point of service to the point of utilization.
Specifically, section 14.35 of MG-1 address the application of 220V induction motors on 208V systems. This section warns that 220V motors applied on a 208V system will operate "successfully", but not efficiently and if the nominal voltage falls slight below 208V, the motor will operate outside of its design tolerances. It recommends that motors applied on a 208V system should have a nominal voltage rating of 200V.
Hope this helps.
The drive manufacturer was of limited help.
The motors are new 60hz. The equipment supplier has said that the manufacturer told them the 208V will be OK. They don't want it to ever fall below 200V. I can control the voltage drop. What is a typical utility voltage variation?
When I go back to the site I will check the actual voltage.
The motors are new 60hz. The equipment supplier has said that the manufacturer told them the 208V will be OK. They don't want it to ever fall below 200V. I can control the voltage drop. What is a typical utility voltage variation?
When I go back to the site I will check the actual voltage.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
I can't even tell you how many 230V motors I've seen burn up that we're put on a 208V service. Even those with supposed built-in buck-boost capabilities. It would be nice to see manufacturers start being responsible and build more 200V motors, since 99% of commercial US services use it (vs. 240V, which is mostly residential).
Maders
Member
- Location
- Boston, MA
The utility must guarantee the voltage to be between +5% (218V) and -5% (197V) (per ANSI c84.1 Table 1 "Range A") at the point of service, but it will be lower* at the point of utilization within your building.
* I'd assume as low as -10% (187V) to account for 5% voltage drop within the building.
Manufacturers produce what buyers buy. Or they wouldn't remain in business.
It' easy to remain in business when all the manufacturers are doing the same thing. Doesn't make it right.
And unfortunately, most of the people buying the equipment don't know any better.
kwired
Electron manager
- Location
- NE Nebraska
I think your 99% is a little high, though I do agree there is likely more 208 systems then 240 systems (in the light commercial applications), but there is a lot of 480 volt systems out there as well.
Most general purpose motors I run into are usually rated 208-240/480 volts, and HVAC equipment is usually rated for 208-240 volts as well.
- Status