VFD. XSY AT4 220v 1phase to 380v 3phase advice sort

Which is no surprise as that's what one needs to generate 400VAC phase to phase 3-phase if one wants the "neutral" point to stay fixed. If the "neutral" can vary then one can get away with 565VDC.

Except for very low power VFDs I would think that a front end PFC is a simpler way of producing higher DC link voltages. The circuit is more compact and doesn't need two large flying capacitors and associated switches which may need isolated gate drives. A PFC has the additional bonus that it reduces the filtering required on the mains input to the VFD in order to meet harmonic limits.

Andrew

Undoubtably true, but the unit is 2.2kW and whilst all the semis are hidden on the heatsink just doesn't look big enough to have both a switching 230AC to 400DC converter plus all the 400V 3ph drivers? Can only see one quite small transformer.

What voltage rating are the two caps?

Seems to me that there is needed both smoothing caps at 230V and at 400V even with a switching voltage boost.

Greg, I’m wondering how you solved your P00 220v issue.

I purchased another AT4 sometime ago and have only just got round to checking it.
It was supplied with P00 = 220 and I’m unable to increase above this value. My other two AT4s were supplied I believe with P00 = 380

I’ve queried this with the supplier and received a couple of responses. One states P00 is the input voltage! I’m asking them to reconfirm this and to clarify whether P02, which is Intermediate Voltage in the manual, is supply or output voltage.

Hi I have an at4 vfd and I have been wiring it up and seem to be getting 500v output.seems very high.any help would be much appreciated.thanks

What are you measuring it with and is a motor connected?

Most normal multimeters will not measure the PWM output of a VFD accurately. As a minimum you need to use a True RMS voltmeter.

Robert

As Robert points out the voltage of a true sine wave AC supply is usually given as an RMS (root mean square) value. For 230V mains this means the peak voltage is the RMS voltage multiplied by the square root of 2, 325V. For a 380V RMS true sinewave the peak voltage will be 537V. For a VFD where a circuit chops the voltage to give an approximately sinusoidal voltage it would be likely that the peak is close to 500V. Without a load to feed it is possible that there are smoothing capacitors on the output that are charging to this peak voltage but not being allowed to discharge and so reach 500V and stay there. As the peak of a 380V AC supply is over 500V I would not worry about connecting a 380V motor to this VFD as they are built to take this voltage.

RMS is the voltage of an AC supply that has the same output power as a DC supply at that voltage. A 230V RMS AC supply will cause the same heating effect in a 1kW heating element as a 230V DC supply. It is based on the area between a sine curve on a graph and the line passing through the centre of that sine curve. For an AC voltage that line is usually the X axis. This is how the square root of 2 ratio of peak to RMS is mathematically derived.

Martin C

I've just joined this Forum because this thread gave me an answer - which I have yet to check - to the same problem that the Original Poster asked - why does the internal potentiometer allows me to run a 4 pole 3 ph motor up to 100Hz but the external pot will only go up to 50 Hz.

In my case I have a motor which is a 2 pole / 4 pole combination to allow 2 speed operation with an appropriate switching of the windings - there are 6 leads coming form the motor. I have done the internal change from star to delta on a previous motor but the thought of dismantling this motor and attempting to locate the star points put me off particularly when I found the AT4 - again a couple of years ago and have only got round now to trying it out.

So thanks to all of you who previously fully discussed this out, and I am hoping the guidance will work.

Rob

Yep - the guidance works!! Again so many thanks even if those in the 2020 discussion are no longer seeing this.

The relevent list came from James Walker's posting of 25/05/2020, with particular reference to the settings for P73 and P74 - just how anyone found that these particular parameters are the key ones for this I just gasp at !!!

Rob

Welcome to the forum.
Thanks for letting us know your outcome. Often the original poster never responds with th outcome wihich sometimes make you wonder if it is worth taking the time to post an reply.

Robert.

Thanks for that Robert - one then starts to think about the possible number of times you've fallen into that catergory; I do try to the polite thing but I'm sure I have been a guilty one too.

But the other aspect is that you have shared your knowledge and, as in this case, I searched 2 years after the original discussion and found a treasure trove of info.

i'm restoring a 1970's planer / thicknesser (for wood!) which has two 3 ph motors requiring the appropriate inverters.

Rob

@Robert G - On my mill the turret moor is is a Dahlander motor which means it is dual speed without having two windings. Anyway I leveraged those two full speed ranges with the VFD by adding a mechanical switch to switch the winding connections. It means I can leverage a lower speed while keeping the VFD stresses down on the old motor.

This is possible with the AT4 as it is a simple Voltage/Hz style VFD which are able to run multiple motors of the same type at once. As compared to a Vector VFD which is tuned to the specific motor parameters. And when you switch poles those parameters change.

There is one rule you need to live by so you dont blow your VFD, NEVER CHANGE THE POLES WHEN THE VFD IS DRIVIG THE MOTOR. The motor must be stationary and the VFD idle.

cheers - James.

Many thanks James for your comments and guidance.

I did expect this motor for driving the thicknesser rollers of the machine to be a Dahlander winding, but measurements show two seperate sets of coils; seemingly this is quite a popular format for large cooling fans, where a simple thermostat, and no electronics, will enable a higher cooling rate when required.

The motor, perhaps like yours, is probably classifiable as old but as it was also capable of running at 2800rpm, I'm using the 4 pole windings and taking the top frequency up to 100Hz. It's not going to be used on a commercial basis, just amateur, so won't get used heavily.

Out of interest how did you discover that it was P73 and P74 that had to be changed to get the external variable voltage to the bigger range?

Rob

Based on the description in my manual I figured that was probably what is was. Did some tests which proved my interpretation correct.