Runnig 50HZ motor on 60HZ

[Darren]

Ok guys I am sorry if I am going over a previously discussed issue but here it is anyway.

 

I want to know the REAL effects of running a motor rated 380V 50HZ on 480V 60HZ. Also how about a motor that is rated same voltage just different frequecny?i.e. 480V 50HZ running on 480V 60HZ?

This all relates to machine tools, having hydraulic pumps and coolant pumps, being imported to America from all around to globe.

thanks for your time.

[jraef]

What matters is speed and saturation. 60/50 = 120%, so a motor rated for 50Hz will spin 20% faster at 60Hz, and vice versa (actually, a 60Hz motor spins 17% slower, but the math is the same). That is apparent on the nameplates when you see that 50H 4 pole motors are 1500RPM (synch), whereas 60Hz motors are 1800RPM. 1800/1500 = 120%. So if it is a pump, that generally means more pressure or flow, especially positive displacement pumps as are often used in HPUs and coolant recirc applications. Of course, the converse is also true, a 60Hz motor fed with a 50Hz supply will spin 17% slower, which means less pressure / flow.

 

Saturation is the ratio of volts and frequency. A 380V 50 Hz motor's ratio is 380/50 = 7.6V/Hz. A 460V 60Hz motor is 460/60 = 7.6V/Hz as well, so that means there is no problem doing that changeover from that standpoint.

 

So if your system can take the added flow/pressure, use 380V 50Hz motors and design around minimum requirements at that speed, then live with the added pressure when used in the US.

 

A 460V 50Hz motor however would be 460/50 = 9.2V/Hz. So if you use that motor at 60Hz, it will be over saturated, which means a lot of extra heating. If you (theoretically) use a 460V 60Hz motor and send it to some mythical land where they have 480V 50Hz, the motor would spin slower and have less torque at that speed, which means less HP, and ultimately less flow or an overloaded pump.

 

I said theoretically because I know of no country using 480V/50Hz, nor do I no of any motor manufacturer making that ratio either. If you think you saw that, you were likely misinterpreting the nameplate data.

 

Here is a website with a decent chart of world industrial voltages.

http://users.pandora.be/worldstandards/ele...ty.htm#3voltage

[marke]

Provided that you keep the V/Hz ratio equal to the design v?Hz, you wil have no problems except:

As you increase the frequency, the motor speed and power rating increase. (P = TxN and at a constant V/Hz, torque stays constant down to around 20 Hz)

 

If you reduce the frequency below rated frequency and keep the V/Hz constant, you wil have reducing cooling on the motor and you will need to begin to derate the motor below the rated torque due to the reduced cooling. Note, the rated power reduces with frequency for constant V/Hz, plus there can be additional derating due to reduced cooling.

 

Best regards,

[Darren]

Thanks for the replys.

The 480V 50HZ motor was just as an example to get the effects of same voltage different frquency. I just wanted to know what would happen then.

Anyway great site where we can all learn from others.

Thanks Again

[Darren]

how close to the design V/F ratio must it be? is there a rule of thumb? give a % please

thanks

[marke]

Hi Darren

 

The motor should be able to operate at the rated frequency with a voltage 10% above nominal. This means that for the V/Hz, you should be able to operate at +10%, however, with small motors, there is a tendency for them to be already overfluxed and I have seen many small motors that will not operate continuously at +10% without overheating.

 

Best regards,

[jOmega]

Consider that a 380/50 and a 460/60 motor have the same v/hz — i.e., 7.66666 v/hz (NEMA motors are 460v — not 480v).

 

Therefore, if you set the max volts at 460 and max frequency at 60 hz .... you will operate the motor at the same v/hz ...(assuming the drive design is based upon a linear v/hz relationship).

 

How much deviation from the ideal v/hz you can operate with... is dependent upon the design/construction features of the subject motor. For example— motors with less iron will be less tolerant of a fat v/hz....... while motors with more iron will be more tolerant. Reason being: with less iron, the motor will tend to saturate sooner .... with more iron ... it will saturate later.

 

So, when unsure of how much deviation in v/hz your motor will tolerate you can let the motor current guide you.

 

At a given operating point—speed and mechanical load— raising or lowering the v/hz, from the motor's ideal value, can cause an increase in the current drawn by the motor.

 

If increasing the v/hz pushes the motor into saturation the amps will increase ..... Likewise, with a fixed mechanical load, decreasing the v/hz will cause the amps to increase as the motor slips more to support the mechanical load.

 

This concept is defined by a parabola ...(see figure)

 

http://jomega.dridoc.com/drives/Images/v-per-hz%20Deviation%20vs%20Mtr%20Current.JPG

 

So, keep an eye on the current; it will help to keep you out of trouble.

 

Kind regards,

jOmega

[Darren]

This application is not using a drive.

[jOmega]

Darren:

 

Historically, those motors are sized by the OEM Machine Tool manufacturer based upon the mechanical loads in a 380/50 system .

 

I've seen many such motors burned out or mechanical equipment damaged (i.e. pumps, etc.) when the M.T's arrive on the shores here and are installed in a 480/60 service .... which can be anywheres from say 455 to 495 or even 500 vac ....

 

Jraef's and Marke's previous posts should be given due consideration. May save you from having to make a costly replacement.

 

Not as concerned about spindles and such but am concerned about pumps and infeeds, etc. .... motor may have to be belted or geared down to get to the original (380/50) operating speed for the pumps and/or feeders ...

 

Of course, that assumes that there is physical room to make such accommodation.

 

It might be more practical to add a VFD .... and solve the problem that way ....rather than to Mickey-Mouse around with a mechanical solution .... or worse.

 

Oh, and don't overlook the electrical capacity afforded by the machine tool ... i.e. fusing, wire sizing, starters, overloads, circuit breakers, etc ...

 

I suspect you'll find that there is justification for such a VFD solution when you consider having to make mechanical modifications ... or have to replace a failed motor or driven mechanical equipment.

 

 

Good luck

 

jOmega

[sp111]

Hi - your post was very helpful. I have a question about running 380V/60Hz appliances (such as vacuum cleaner, toaster, coffee maker, lamps, fans, etc. ) on 380V/50Hz supply? would it work? do we need to take any special precautions? Many thanks.

 

What matters is speed and saturation. 60/50 = 120%, so a motor rated for 50Hz will spin 20% faster at 60Hz, and vice versa (actually, a 60Hz motor spins 17% slower, but the math is the same). That is apparent on the nameplates when you see that 50H 4 pole motors are 1500RPM (synch), whereas 60Hz motors are 1800RPM. 1800/1500 = 120%. So if it is a pump, that generally means more pressure or flow, especially positive displacement pumps as are often used in HPUs and coolant recirc applications. Of course, the converse is also true, a 60Hz motor fed with a 50Hz supply will spin 17% slower, which means less pressure / flow.

 

Saturation is the ratio of volts and frequency. A 380V 50 Hz motor's ratio is 380/50 = 7.6V/Hz. A 460V 60Hz motor is 460/60 = 7.6V/Hz as well, so that means there is no problem doing that changeover from that standpoint.

 

So if your system can take the added flow/pressure, use 380V 50Hz motors and design around minimum requirements at that speed, then live with the added pressure when used in the US.

 

A 460V 50Hz motor however would be 460/50 = 9.2V/Hz. So if you use that motor at 60Hz, it will be over saturated, which means a lot of extra heating. If you (theoretically) use a 460V 60Hz motor and send it to some mythical land where they have 480V 50Hz, the motor would spin slower and have less torque at that speed, which means less HP, and ultimately less flow or an overloaded pump.

 

I said theoretically because I know of no country using 480V/50Hz, nor do I no of any motor manufacturer making that ratio either. If you think you saw that, you were likely misinterpreting the nameplate data.

 

Here is a website with a decent chart of world industrial voltages.

http://users.pandora.be/worldstandards/ele...ty.htm#3voltage

[marke]

Hello sp111

 

Welcome to the forum.

 

The major issues are with AC magnetic devices such as transformers, relays and induction motors.

Many domestic appliances use universal motors and these are not affected by the frequency.

Transformers can be an issue if they are wound for 60Hz only. Some are wound for 50/60Hz.

The name plates should specify if they are a 50/60Hz rated or 60Hz only.

 

Best regards,

Mark.

[leon70]

Dear Friends,

 

I have a problem related with this. I have a glass process machine imported from europe with their motors set to 50 Hz and 380 V. I have currently only an electric supply of 2 phase 220 V . Machine control board operates with 24 V AC. Is it imperative to get a 440V 3 phase supply or there are other possibiliites?. What would be the complications?

[leon70]

Dear Friends,

 

I have an issue related to this. I have a glass prcessing machine imported from europe with their motors set to 380 V. 50 Hz. I have only an electric supply of 2 phase 220V. Machine control board works with 24V AC and it indicates 50/60 Hz. Is it imperative to get a supply of 440 V or there are another possibilities? What could be their implications?. Thank you very much in advance for your help

[AB2005]

Dear Friends,

 

I have an issue related to this. I have a glass prcessing machine imported from europe with their motors set to 380 V. 50 Hz. I have only an electric supply of 2 phase 220V. Machine control board works with 24V AC and it indicates 50/60 Hz. Is it imperative to get a supply of 440 V or there are another possibilities? What could be their implications?. Thank you very much in advance for your help

 

Hello leon70

 

Your question is not cleared, your motor is 2 phase 220V but you are asking for 440V?

If you want to run 380V designed motor on 220V available supply, you should purchase a VFD with two phase input and three phase out and program its V/HZ ratio accordingly.