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Old January 10th, 2019, 01:41 AM   #1
skyfox
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Question regarding 400VAC vs 480VAC?

Happy new year everyone.

This is more of a Electrical engineering question than a PLC one.

Can a Motor and a VFD that is rated for 240/480 60/50Hz operation be used on a system that has utility supply power of 3-Phase 400VAC? Customer is dictating 400VAC transformers for both their US and overseas factories? However, control cabinet electronics being used for powering the PLC, 24VDC Power Supplies etc., are running off from a 120 V step down from this very same 400 VAC transformer.

Can this be done or do I need to look for a VFD and a motor that is rated strictly for 400VAC use?

Thanks.
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Old January 10th, 2019, 05:30 AM   #2
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So many things going on here.

240/480, is that the split-phase way of generating 2 phases from a single phase transformer ?
I ask because normally there is a squareroot of 3 ratio between voltages in delta/triangle configuration, not a factor 2 ratio (240/480).
Apart from that, a VFD can be used for voltages below the maximum rated voltage.
The question is what about the motor(s) connected on the output-side of the VFD. What are they rated at ?

The way you described the rest it sounds to me that the customer expects a 3-phase power supply. Not a split-phase power supply.

The industry standard is that single phase control voltage is generated by a dedicated transformer.

Also, it sounds strange that they "dictate" 400VAC transformers for the use in the US where the standard voltage for 3-phase supply is 480V or 600V.
It is quite normal for machine manufacturers that supply to all over the world to have control voltage transformers have multiple taps so that it can be adapted to the voltage used in a particular country.
For example a control voltage transformer can be connected to any of 220/230/380/400/414/440/480V and still output 120V.
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Old January 10th, 2019, 05:46 AM   #3
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I work on quire a few machines from Italy, Germany and China - where 400V is the norm.


These machines need a 480 - 400 3 transformer for their power. A 480V VFD fed 400V will fault for buss undervoltage. Frequently they are built without a control voltage transformer - 400V usually has a neutral that gives 200V and a DC power supply input is rated up to 250V. Rarely is there anything in the panel that is 120V.


Short answer = No. Tell the customer they need a transformer.
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Old January 10th, 2019, 06:38 AM   #4
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Quote:
Originally Posted by Aabeck View Post
These machines need a 480 - 400 3 transformer for their power. A 480V VFD fed 400V will fault for buss undervoltage.
The VFDs I use calculate the DC Link voltage based on the supply voltage you specify when configuring the drive. And then you can even tweak that setting if you want to.
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Old January 10th, 2019, 06:42 AM   #5
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Quote:
Originally Posted by Aabeck View Post
Frequently they are built without a control voltage transformer - 400V usually has a neutral that gives 200V [..]
The industry standard is to use a control transformer.
The reason is that the shorcircuit current of the incoming power supply is normally much higher than what the control components are rated for. So you need to bring down the short circuit current by some means - hence the control transformer.
Just using the neutral in the incoming supply is only done on extra-small machines. And many companies straight out specify that a control transformer is mandatory.
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Old January 10th, 2019, 08:11 AM   #6
Gene Bond
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Most 400v supplies I've seen referenced are 50hz. Are there any motors or other components which will gt upset by 400v/60hz in the system?
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Old January 10th, 2019, 09:46 AM   #7
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Quote:
Originally Posted by skyfox View Post
Happy new year everyone.

This is more of a Electrical engineering question than a PLC one.

Can a Motor and a VFD that is rated for 240/480 60/50Hz operation be used on a system that has utility supply power of 3-Phase 400VAC? Customer is dictating 400VAC transformers for both their US and overseas factories? However, control cabinet electronics being used for powering the PLC, 24VDC Power Supplies etc., are running off from a 120 V step down from this very same 400 VAC transformer.

Can this be done or do I need to look for a VFD and a motor that is rated strictly for 400VAC use?

Thanks.
Are you asking about the control power or are you asking about 3 phase motors? You cannot use a VFD to supply anything other than a motor, so if your question was about the control power, then leave it as they have it.

But you seemed to indicate that you have 3 phase motors. If so, then the problem with the VFDs is that the output voltage from the VFD can’t be higher than the input voltage. So if the input is 400V, that’s the highest output voltage too. For the motor then, assuming the motor is rated for 460V 60Hz (motors are never rated for 480V), you will have to limit the output frequency to the same V/Hz ratio that the motor is designed for. In this case 460/60 = 7.67 V/Hz so 400/7.67. = 52Hz as the maximum speed. Any higher and you are running the motor in a field weakened state, so torque will drop at the square of that change, the motor will draw more current to do the same work and eventually cook itself.

Now IF by chance they actually used motors that were DESIGNED for 400V 50Hz and were SAYING that they were “OK” for 480V 60Hz, then you are OK, but again, limited to 50 Hz output. So it really depends on exactly what the MOTOR NAMEPLATE says, not the sales literature.
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Old January 10th, 2019, 03:27 PM   #8
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Quote:
Originally Posted by skyfox View Post
Happy new year everyone.

This is more of a Electrical engineering question than a PLC one.

Can a Motor and a VFD that is rated for 240/480 60/50Hz operation be used on a system that has utility supply power of 3-Phase 400VAC? Customer is dictating 400VAC transformers for both their US and overseas factories? However, control cabinet electronics being used for powering the PLC, 24VDC Power Supplies etc., are running off from a 120 V step down from this very same 400 VAC transformer.

Can this be done or do I need to look for a VFD and a motor that is rated strictly for 400VAC use?

Thanks.
Agree with @jraef, I think that what he says is correct. But I would listen to the experience from @Aabeck, since the idea is to make everything reliable. Commissioning has enough problems with everyone doing their best to avoid trouble ... no need to ask for more problems!

I'll split this into motor and VFD opinions:

A 480V motor will run .. fine .. if the power source is solid .. from a 480V VFD. If only 400V is available, you won't get rated horsepower, since your output voltage is low. I would over-size the motor and VFD in this case by 20% and pay attention to what the maximum output speed of your motor is expected to be.

A 400V motor will work fine on a 480V three phase VFD. The 400V motor will have 20% higher Full Load amps. So I'd still over-size the VFD (output amps) by 20%

A 480V VFD will run on 400VAC input, but it will have less tolerance for under-voltage conditions. So you may get some nuisance trips on under-voltage when everything is actually OK. Look at the specifications on your VFD to see what tolerance it has for under-voltage, and compare that will the expected sag on your electrical system.

I would source 400V VFDs just so that things are as reliable as possible. Particularly for a new plant. In my HUMBLE opinion ... You'd have to be saving a *LOT* of money, time, warehouse costs, delivery time, or whatever ... on VFDs and motors to use 480V instead of 400V

As for the 24V and the 120V, you can get control transformers for 400 - 120 or even 400 - 24. I don't see an issue. These are cheap so get the right ones.
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Old January 10th, 2019, 04:12 PM   #9
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Jesper,

I always use a control transformer, but somehow the engineers in Europe and Asia seem to think the 200V is fine to use, just fuse a lead and run it to the 24V power supplies, programmer power outlets, temperature controllers, and anything else rated for 100 - 250V input. And I am not referring to small machines, some of these are multi-chamber processing lines.

I have more than once added a transformer for 120V items during updates for customers.
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Old January 10th, 2019, 05:14 PM   #10
GaryS
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400 v 50Hz or 480 V 60Hz is all the same 8 volts per hertz
The base speed of a 4 pole 50hz motor is 1500 rpm
The base speed of a 4 pole 60hz motor is 1800 rpm
If you run the 50hz motor at 60hz it will run at 1800 rpm
On 99.999 % of the time the motor will never notice a difference. On the very few occasions ( I have never run into one of them in over 40 years in the trade ) you may see an increase in the temperature in the 60hz motor running on 50hz due to less air over the motor if the motor is overloaded. If that’s the case then the motor is undersized from the start.
Both motors are designed the same, over here we like just lead wires to connect the motor in Asia they like the term block with stuts and jumpers. Both motor work the same. Thee speed of the motor is controlled by the frequency of the supply to it 30 hz on a 60hz motor = 900 rpm 90hz on a 60hz motor = 2700 rpm
As for the VFD’s if you read the name plate data. I have not run into one yet that isn’t listed as 400 – 480 V 50-60hz they call them 400 class. Actually some vfd’s can run on pure DC power if connected properly. All vfd’s convert the incoming power to pure DC ( DC Buss) before they switch the output frequency. Most vfd’s can also run up to 400hz output
I actually ran into that a while back 380hz (set in the vfd) I estimated the motor was running about 25,000 rpm the client wanted to know why the motor kept going out ( motor bearings)

All this hub bub about 50 or 60 hz is just designed to confuse the issue. It’s a choice that was made when the power grid was originally designed at that time nobody thought we would be sending machines or motors all over the world. Then the add to the confusion here in north east us we have a grid running at 25hz it’s been running since the early 1900’s.
I know of one company that received a machine from Europe with a rating of 400v 50hz were told that they needed exactly that to run the machine so the spent almost as much as the machine for a rotary converter. I have worked on many machines rated for 400v 50hz connected directly to 480 60hz supply been running fine well over 20 years without problems.
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Old January 10th, 2019, 08:03 PM   #11
skyfox
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Quote:
Originally Posted by JesperMP View Post
So many things going on here.

240/480, is that the split-phase way of generating 2 phases from a single phase transformer ?
I ask because normally there is a squareroot of 3 ratio between voltages in delta/triangle configuration, not a factor 2 ratio (240/480).
Apart from that, a VFD can be used for voltages below the maximum rated voltage.
The question is what about the motor(s) connected on the output-side of the VFD. What are they rated at ?

The way you described the rest it sounds to me that the customer expects a 3-phase power supply. Not a split-phase power supply.

The industry standard is that single phase control voltage is generated by a dedicated transformer.

Also, it sounds strange that they "dictate" 400VAC transformers for the use in the US where the standard voltage for 3-phase supply is 480V or 600V.
It is quite normal for machine manufacturers that supply to all over the world to have control voltage transformers have multiple taps so that it can be adapted to the voltage used in a particular country.
For example a control voltage transformer can be connected to any of 220/230/380/400/414/440/480V and still output 120V.
Thanks for the Reply.

Sorry I probably misstated or didn't do a good job of explaining.

Incoming power is 400VAC 3Phase.

(Plant power Source. This is a new factory built in the US in 2017 to match the factories this customer have in Indonesia and in Singapore. COPY EXACT PHILOSOPHY)

A 400VAC Transformer is used for steeping down to 120 VAC 1Phase power to power the PLC, 24VDC supplies and some other analytical systems attached to this unit. This unit is in a R&D lab. Recently they have purchased a used Waste Water transfer skid and want to attach it to this system to automate it to waste water from the lab can be pumped out to treatment tanks located outside. So I am trying to size a VFD to control the pump as they want to be able to control the transfer speed. I want have access to pump manufactures label for a month or so to get the relevant info for a month or so because the skid is still in a crate.

All I know is from the general info given that the pump is rated for 240/480 60/50Hz operation. Provided this is correct,based on incoming 400VAC 3 Phase power, Can this motor be run efficiently? Keeping in mind that incoming power is at 60Hz and not 50Hz.


Thanks

Last edited by skyfox; January 10th, 2019 at 08:07 PM.
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Old January 10th, 2019, 08:12 PM   #12
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Thank you all for the replies. I didn't do a good job of explaining my question. Please see my reply to JesperMP above.


Thanks again for helping.
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Old January 10th, 2019, 08:20 PM   #13
skyfox
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Quote:
Originally Posted by jraef View Post
Are you asking about the control power or are you asking about 3 phase motors? You cannot use a VFD to supply anything other than a motor, so if your question was about the control power, then leave it as they have it.
hat change, the motor will draw more current to do the same work and eventually cook itself.

Thanks jraef,


Yes. I was wanting to control a 3 Phase motor that from the information that I have is rated for 240/480 50/60 HZ, and wanted to know if I can control that with incoming 400VAC 3PH 60HZ power using a VFD.

Thanks


Sean-

Last edited by skyfox; January 10th, 2019 at 08:27 PM.
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Old January 10th, 2019, 09:17 PM   #14
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480 v split phase dos not exist 230v split phase is just single phase 220-110 v
taped winding look it you will find many examples
I don't know why anybody calls it split phase it just adds to the confusion
it's only in north America the rest of the world doesn't use it
and to answer your question YES you can use either motor with either power source
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Old January 11th, 2019, 02:15 AM   #15
JesperMP
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To understand this:


So your concern is that you have 400V supply as the system is designed for but at 60 Hz which is not the same as the 50 Hz it is designed for.
And you want to compensate for that by adding a VFD to run the motor at 50 Hz ?

What does it say on the motor name plate exactly ?
240/480 50/60 HZ is odd. You have a factor 2 ratio between what I interpret as delta and star connection, not the usual factor 1.732.
Is it to be interpreted as that at 50 Hz, the motor should be connected to 240V delta, and at 60 Hz the motor should be connected at 480V star ?

It is confusing that you have a system that is designed for 400V, but has a motor where the name plate does not match that.
How was the motor connected in the original system ? As star or delta ?
If it was connected in star with 400V then it was derated if the nominal voltage is 480V. That begs the question why..
It is a strange name plate (if correct), and a strange way to connect it.

Post a photo of the motor name plate.
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