Can you run a 3 phase 220v motor on 208v 3 phase?
Can you run a 3 phase 220v motor on 208v 3 phase?
(OP)
The motor says its a DAVI Asincrono Motor 220/380/440 Rpm 1420/1720 Hz 50/60 8.8/5.1/4.4
This is a motor for a milling machine
any help would be appreciated!
This is a motor for a milling machine
any help would be appreciated!





RE: Can you run a 3 phase 220v motor on 208v 3 phase?
Judging from the markings it's probably Italian so it is equally probably a pile of junk like most of the motors they make
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If we learn from our mistakes I'm getting a great education!
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
Best regards,
Mark.
Mark Empson
L M Photonics Ltd
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
A motor has two limits on the voltage. The lower limit is set by either or both torque and current. As the voltage drops the current must increase to generate the same Watts for the load. If the current gos too high the motor overheats.
Also the maximum torque is related to the square of the voltage so if the voltage is too low the motor may stall or not start.
The upper voltage limit is the magnetic saturation of the motor.
I understand that motors designed for multiple voltages are designed so that the motor will have adequate torque and will be able to safely carry the current at the lower voltage. On the other hand, they are designed to take a higher than normal voltage before saturating.
The current rating is a tip off. 8.8/5.1/4.4 Amps.
Nema ratings are generally in the ratio of 2:1 and IEC ratings are generally in the ratio of 1.73:1.
The 8.8/4.4 A will correspond to the 220/440 Volt ratings at 2:1
The 5.1 A rating will be the maximum current that the motor will carry without overheating and will correspond to 208 Volts.
This motor looks like 220/440V suitable for 380 Volts on the 440 Volt connection at 50 Hz. The maximum current allowed is 5.1 Amps (or 10.2 @ 2:1)
The 220 Volt connection may be expected to draw 8.8A x 60Hz / 50Hz = 10.56 Amps. Close enough 10.2 Amps for me.
Bill
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"Why not the best?"
Jimmy Carter
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
Older motors have less problems on 208 Volts and motors such as mill motors that are seldom loaded to 100% 100% of the time should accept 208 Volts. If there is a problem with overloading a mill on the occasional heavy cut, the overload protection should do its job and trip the motor off. The mill may then be restarted with a lighter cut.
With the newer motors driving loads that will demand 100% of the horsepower rating I would hesitate to use a 230 Volt motor on 208 Volts. 200/230/460 Volt motors are now available for that service.
Bill
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"Why not the best?"
Jimmy Carter
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
The 220/380 are the pre-harmonisation European 50Hz voltages. Looking at the shaft speeds 440V must be a 60Hz voltage for star connection, but the 60Hz delta voltage is missing. With a 208V supply the voltage is at about 80% of what is really needed, and torque will be down to about 65%. If it's a geared head Bridgeport I doubt there will be much left for cutting metal after the transmission losses.
Of course there's nothing lost by trying!
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If we learn from our mistakes I'm getting a great education!
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
The motor voltage standard gives a low of 198 V (or -10%) for a 220 V motor.
If you don't have a big drop between the supply bus (panel) and the motor, then you'll be OK.
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
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If we learn from our mistakes I'm getting a great education!
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
I wondered why some stuff said 230 VAC and some 220 VAC. Thanks for pointing out where it comes from (and the need to also look at frequency)!
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
In this case, the 380 V, 50 Hz rating will be on the same connections as the 440 V, 60 Hz rating. The motor will be slightly over wound to allow the extra current. This will allow the motor to be used on 208 Volts without overheating.
Torque will suffer, but starting and pullout torque. Running torque at full load will take more current which the motor will allow.
This is probably similar to our 200/230 Volt rated motors that have a slightly wider allowable range of V/Hz ratio than a standard motor.
Bill
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"Why not the best?"
Jimmy Carter
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
Bob,
Glad to help a little - I think Gunnar said a while ago that in Europe most systems are running at 400V after harmonmisation but there's still a lot of the UK running on 415V equipment and infrastructure even though we're 'officially' now 400V with a very large tolerance. You'll see 220/380V on older continental machines and 240/415V on older British machines but now everything should be 230/400V.
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If we learn from our mistakes I'm getting a great education!
RE: Can you run a 3 phase 220v motor on 208v 3 phase?
It might work if you don't expect to get full capacity from the milling machine. You could just try it and if (when) it doesn't work replace it.