Can you run a 3 phase 220v motor on 208v 3 phase? 1

[bneal1580]

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!

 

[ScottyUK]

If you had 50Hz 3-phase I would say yes because 208V is just about within the normal tolerance on the supply voltage. I suspect from the 208V that you are in the 60Hz world, likely North America, and in that case the answer is no. The 220V and 380V are standard European 50Hz voltages for delta or star connected windings respectively. The 440V isn't a standard 60Hz voltage as far as I know, but because we can deduce that the windings are connected in star for 440V we can calculate that the voltage you'd need to use this motor on 60Hz in a delta connection is about 254V, which is another non-standard voltage.

Judging from the markings it's probably Italian so it is equally probably a pile of junk like most of the motors they make and if I were you I'd look on ebay for a replacement from one of the decent brands (Leeson, Reliance, Baldor). You can play a few tricks with buck-boost transformers but I'd question whether it is worth either the hassle or the cost for such a small motor. Sorry!


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If we learn from our mistakes I'm getting a great education!

 

[Marke]

I would say yes, you can operate it off 208 volts, but your torque will be down and you would need to be careful not to overload the motor under heavy cutting.

Best regards,
Mark.

Mark Empson
L M Photonics Ltd

 

[bneal1580]

Thank you, this has helped a lot. I am in North America as you suspected!

 

[waross]

I would try it. You give 50/60 Hz as part of the nameplate information.
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

 

[BobM3]

My Bridgeport mill's motor is rated 230/460 3 phase. I've run it for over 10 years now on 208. No problems yet.

 

[rockman7892]

As long as the V/Hz ratio stays the same, does it matter how far off +/- percentage wise the supply voltage is from the nameplate voltage?

 

[waross]

Given the extreme frequency ranges that VFD motors see, I don't see a problem with 50Hz/60Hz changes if the proper V/Hz ratio is maintained. See the FAQ on 50Hz/60Hz conversions for an overview of other issues besides V/Hz ratio. (Thanks to itsmoked.)
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
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Mark / Bob,

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!

 

[stevenal]

Remember that 208 is a nominal voltage. ANSI C84.1 allows the actual voltage to go as low as 191 at the utilization point (range A), occasionally going as low as 184 (range B). Compare this number to the 220 -10% NEMA tolerance for voltage, and you are looking pretty low.

 

[magoo2]

You can expect the nominal 208 V service voltage to get down to 197.6 V (or -5%). The ANSI C84.1 shows a minimum of 197 V.

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.

 

[ScottyUK]

It's a 220V at 50Hz. At 60Hz it is a 254V motor, unless this is a magic motor which doesn't need to obey the volt/Hz relationship which normally apply...


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If we learn from our mistakes I'm getting a great education!

 

[BobM3]

ScottyUK -

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)!

 

[waross]

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)

I see this type of Amp rating on 230/200 Volt and 230/208 Volt rated motors quite a bit, Scotty. The motor is slightly oversized on 230/460 Volt service.
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
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

I'll take your word for it about North American motors Bill! From the word 'asincrono' I think this particular one is from this side of the pond and, being charitable, Italian motors aren't especially generous with either the iron or the copper which is why they run scorching hot then stop working. The Italians do have a nice line in expensive cars though, plus food I love and a climate I envy!


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!

 

[LionelHutz]

Considering this appears to be a European motor, I'd also guess the motor is 220V/380V 50hz and 440V 60Hz just like Scotty first posted. I'd also agree with his later post that you're looking at a motor that will produce about 65% of rated torque running on 208V 60Hz.

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.