Thread: VSD for3 Phase Motor

Keith, thanks for your reply. I am led to believe that some models are designed to take either single or three phase input?
If ,so are these more expensive than a dedicated 3phase input unit?
Or is it that they are just a larger capacity and hence more expensive?

As I understand it the only diference in construction between the two types is that the units specified for single phase input have larger capacitors on the input side. Previously you would just de-rate a three phase VFD by approximately 40% to use single phase input.

As far as cost goes you can check various sites for a cost on a Teco FM50
or AC Tech. When I was researching prices I was set* to buy from Marshall Wolf Automation in Texas. Before the dollar de-valued they were less than half of the local price, a ratio that I find too much to ignore.

The current best units incorporate sensorless vector control to provide a stable motor speed. This is called sensorless becasuse there is no encoder feedback from the motor for speed sensing, the VFD instead monitors for current and approximates constant selected speed (whatever that may be).
Other types will accept an encoder feedback from the motor for very precise speed control, but that gets expensive and may not be of value for a standard lathe.

When buying from a U.S. dealer be aware that there units are typically 240v output, hence the need for a motor which you can connect in 240v delta as already discussed. (There is no inbuilt voltage step-up to 415v in a common VFD...although I have seen some units that have a transformer incorporated. A stand-alone three phase 240v/415v transformer of maybe 3 KVA would be needed for a 2.2kW motor.

The better units have easily settable parameters for things like speed ramp up/down...a great thing for threaded chuck mounts. Also available are external braking resistors for quick spindle stopping which would be useful for threading on a lathe with a camlock spindle nose.

*I am not currently running a VFD, opting instead for a brushless AC servo for my lathe. I still have a new 2.2 kW motor which I may use for another VFD powered project.

Good luck with your project.

Greg

http://www.wolfautomation.com/ No affiliation, just a recommended dealer according to other inernet users.

Many thanks again gregoryq, have you any suggestions regarding filters to stop any problems on the supply?

Hi Inventor-

No help on the line filter I'm afraid. There are many on the market, single or three phase input, and various voltage ratings.

On the advice of some more experienced hands I am not planning to incorporate one unless it becomes plain that I need one. I am unaware if the C-Tick approval rests on having a filter in an installation.

On my servo installation there is no requirement unless a CE approval is needed, then the filter and factory original cables are required.

Schaffner is one maker of filters...they can also be bought under the Allen Bradley brand and I'll bet others too.

I imagine that if you deal with a full service dealer they can provide you with better tips. Try Beckie at Marshall Wolf

Greg

Gregeryq, thanks, I much appreciated your time and assistance.

Hi INVENTOR,
I have attached some data on VFD's where they show the various filters etc that can be needed for a VSD.

Regards,
Keith.

Keith, thanks for your effort, I will have a read.