Frequency Conversion

Hi,

I am trying to operate a piece of equipment that was designed for use in Europe in the United States. The equipment is known as a fluidized bed and consists of a turbine, a pump and two heating elements. The turbine and the pump are designed to be operated using 3 phase 380 V, 50 Hz power. The heating elements are wired in such a way that they operate using single phase 280 V, 50 Hz power. I have attached the electrical schematic of the fluidized bed to this posting.

My electrical supply in the US is 3 phase 480 V, 60 Hz and I have considered a number of options for running the machine in our facility. I contacted one company that designs rotary phase converters, they suggested that 480 V, 60 Hz was equivalent to 380 V, 50 Hz and that I did not need a phase converter to run the instrument. They had not seen the electrical diagram, but some electrical engineers who looked at the diagram suggested that 480 V, 60 Hz would probably not work. They are worried that the control elements, which are not shown in the electrical schematic, could be operating off of the line frequency.

I also contacted three different VFD manufacturers. Two of them believe that they can convert 480 V- 60 Hz to 380 V-50 Hz, but they believe that the presence of the single phase heating elements operating off of 220 V will cause the VFDs to shut down. A third VFD manufacturer has described a custom solution for the problem, but I do not understand the proposal. They want to make a VFD that operates using 220 V input, but creates 380 V output at 50 Hz. They think that this will prevent the VFD from shutting down. I don't really understand enough about electricity to evaluate this proposal. In order to operate the VFD, do I need to convert our 480 V, 60 Hz to 220V single phase. How will that prevent the VFD from shutting down?

I would appreciate any insight into the best way to handle the issue. Replacing the pump, turbine and heating elements is not a very convenient option. Is the custom VFD proposal promising?If not, any direction would be greatly appreciated.

https://drive.google.com/file/d/0B3RbBMxUS0_hc3VqWTdHbEZvOVU/view?usp=sharing

Get a 480 to 380 transformer. Pretty common stuff for European machines.

Hi,

Thanks for your reply. Do you have a specific model that you can recommend? The total power requirement is slightly less than 4 kW. At the peak, it draws 16 Amps.

The few that we have came with the machines. I would check with a large electric supply company or online.

greggv said:

Get a 480 to 380 transformer. Pretty common stuff for European machines.

Click to expand...

Transformers dont transform Herz


I was told by my motorrepairshop a 440volt 60 Hz motor is phisicaly the same as a 400volt 50Hz And i did connect some 440 V 60Hz motors on 400V 50 Hz without problems

For the heating elements I would use a seperate transformer

And a VFD for each motor So they keep the same speed
Most modern VFD`s you can programm what voltage and Hz the connected motor is and it will regulates voltage and Hz accordingly
And as your incomming voltage is higher as motorvoltage you will not have powerproblems

Peter from holland

Thanks for your reply. My understanding is that this particular piece of equipment is sensitive to frequency. I don't have the equipment yet, but the electrical schematic seems to indicate that the 220 V single phase and the 380 V, 3 phase are drawn from the same power supply, but are wired in different configurations.

I have created a link to the electrical schematic, the file attached to the original post does not show enough detail.

Thanks again.

https://drive.google.com/file/d/0B3RbBMxUS0_hc3VqWTdHbEZvOVU/view?usp=sharing

Acc. the drawing your heaters are powered with 2 phases 380 volts and are 0.88Kw each
So get a 2phase transformer 480 to 380 for the heaters and if the transformer for the controls has no 480 taps use the same transdormer for the controls
You have a transformer for the contols 380 to 220 volts on the far right on the drawing


Peter from Holland

Peter,

Thank you for looking at the schematic and sharing your insights. I guess I was misinterpreting the diagram. I was under the impression that the heating elements were operating off of single phase 220V. I am not really familiar with 2 phase electricity. I was also assuming that the transformer to the far right was involved in controlling the heating elements, and that the control elements were not depicted. Are you saying that I should get two pieces of equipment: 1) A three phase VFD for the motors to provide 380 V, 50 Hz, and 2) a two phase transformer for the heating elements and possibly the control elements?

I am not familiar with two phase electricity. I thought that everything was either single or three phase. I'll do some research.

Thanks.

Wheather one has 1 phase and a neutral or 2 phases makes no difference
You need 220volts between 2 wires A voltmeter sees no difference
This diagram only shows the powercircuit not the controle circuit
That should be on the next page connected to the 2 leads of that transformer

I see a lott of wirediagrams in US equipment and thats a PITA to find out how it works and finding problems
A logic diagram is much easier to read once you get the hang of it

Peter from holland

I am going to try to get the full diagram. This particular instrument was actually made in Germany and used in Holland. I am having it shipped to the United States.

For getting it to work you also have to check that all the components on the controle side are 60 Hz compatible

Peter from holland

My understanding is that the control components are not 60 Hz compatible. That's why I wanted to get a VFD where I can set the output voltage at 380 V and the output frequency at 50 hz. The problem is that the VFD manufacturer is telling me that the VFD cannot be used to power the heaters; it can only function with motors.

Ideally, I would need a piece of equipment that could convert the 480 V, 60 Hz to 380 V, 50 Hz, but would also function when the single phase elements (heaters) draw from it. A Chinese VFD vendor suggested that they could accomplish my needs by creating a VFD that is powered from single phase 220 V, 60 Hz electricity, but the output can be set to three phase 380 V, 50 Hz. I don't understand why single phase input voltage would allow this VFD to handle single and 3 phase loads simultaneously. If it would really work, I would happy to buy it.

An American VFD manufacturer suggested that we need more information about the feedback from the heating elements. They thought that we might be able to accomplish it with a 3 phase input VFD, but more information might be needed.

I don't know enough to be able to distinguish between the merits of the two proposals.

A VDF is perfect for powering 1 motor at a time
What components are not 60Hz compatable you think
Most contactors are
Perhaps raizing voltage a bit on the controle transformer to make them last

Peter from Holland

I was told that the heating elements would be fine with 480 V and 60 Hz. Contrary to my original statement, they are currently running on 380 V, 50 Hz single phase (2 phase). The pump should also tolerate 480 V, 60 Hz. The manufacturer, however, believes that the turbine will not tolerate 60 Hz. According to the manufacturer, there are also 4 relays in the control system that are not going to be able to tolerate 60 Hz. We are also not sure whether the internal transformer for the control system could tolerate the U.S. voltage, but it might. The main problems are the turbine and the relays.

Well
Question is is the turbine direct driven or with V-belts or the like
you could change those so the turbine itself turns the original speed
Otherwise you could wire in a VFD
That would also eliminate the need for at least 1 contactor
Also how old is this machine
If it is less than 10 years all components are 400 Volts
We changed from 380 to 400 volts at least 10 years ago


Peter from Holland

I am not certain how the turbine is driven, but I will look into that. The machine was built in 1983.

I'm not able to see the diagrams clearly due to such small size, so I can't address any details that may hide in there, however, if it were my issue, my path of resolution would be to install a VFD to operate the turbine, reconfigure the wiring connections of the heating elements to be as close to 240 as I could get (they're a resistive load, right?) and change out any small devices that cannot tolerate 60hz.

Relays are basically resistive, so frequency tends to not affect them. There are a few 'special purpose' relays that have timing, voltage or current sensing character, in which case, control frequency CAN be an inssue.

While most will be fine at 50 or 60 hz, There are SOME contactor coils that don't like to be operated outside their design frequency. Contactors are unique devices in that the magnet pulls on an armature which is inductively coupled to the coil. When initially powered on, they draw a modest AC current to pull in, but once in, the armature physically closing changes the inductance of a resonant circuit, which increases the contactor's holding power, while at the same time, limiting the control coils current flow substantially. Operating a contactor coil outside of it's intended frequency range results in the coil operating outside it's expected current and voltage, hence, they can self-destruct... but most 'modern' contactors aren't that picky.

If all this machine consists of, are some resistive heating elements, one AC motor, and some simple controls, it should not be a difficult conversion.

Thank you. You might be able to see the diagram more clearly through this link:

https://drive.google.com/file/d/0B3RbBMxUS0_hc3VqWTdHbEZvOVU/view?pli=1