220V equipment on 208
- Thread starter olc
- Start date
curt swartz
Senior Member
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
The manufacture is the only one that can answer that question. Where is the unit from? Are you sure its designed for 60Hz? 220 volts is more common on 50Hz systems but sometimes 60Hz systems.
Elect117
Senior Member
- Location
- California
- Occupation
- Engineer E.E. P.E.
Yes
Motors can usually still operate as expected within 10% of their nameplate voltage rating. It can create more heat and reduce the life span of the moto. It will also draw more current at the lower voltage and you will need to stay on top of the voltage drop from the service on down. If you are at 205V with load then you could end up with the motor dropping out. You might need to keep the service lightly loaded and increase the conductor size to ensure you don't have any low voltage issues.
Motors can usually still operate as expected within 10% of their nameplate voltage rating. It can create more heat and reduce the life span of the moto. It will also draw more current at the lower voltage and you will need to stay on top of the voltage drop from the service on down. If you are at 205V with load then you could end up with the motor dropping out. You might need to keep the service lightly loaded and increase the conductor size to ensure you don't have any low voltage issues.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
This is important, because if the equipment was MADE HERE or FOR HERE using typical NEMA designed motors, most NEMA design motors 5HP and below are built to accept 208V, knowing that this is a common 3 phase voltage here. It will state that on the motor nameplate and show different FLC values at 208V or 230V.
But that does not hold true for things made overseas that are designed PRIMARILLY for an overseas market, where nobody else uses 208V. As Curt says, they are also likely designed for 50Hz and although some will state that they can be run at 60Hz, that gets way off base if you have 208V.
Motor torque is a function of voltage and frequency, expressed as a ratio of V/Hz and will generally be fine if that ratio is +-10%. A motor designed for 220V 50Hz is 220/50 or a 4.4 V/Hz ratio, so it will provide rated performance at a ratio of 3.96 to 4.84. That motor connected to 240V 60Hz supply will get a V/Hz ratio of 4.0, so it will work fine. But at 208V 60Hz, it is getting a 3.47 V/Hz ratio, which is 13% lower than acceptable. That results in the motor having only around 87% of it's rated continuous torque and 75% of it's rated peak torque (used to accelerate or re-accelerate a change in loading). That means it will not be able to handle the same load without drawing excess current, leading to an overload and/or a shorter life span.