Cheap VFD

[John MC]

On John MC Said:

I agree with Dave (SoD), we need to be careful talking about VFD installations, that is to say, not giving the impression that its easy.  The instructions for VFD’s originating from the far east leave a lot to be desired.  My last VFD installation, far eastern device, was complicated by mistakes in the instructions.  Luckily I spotted them, this forum was tremendously useful for sorting this out.

For someone not able to to wire a VFD, what do they do?   Easy enough to find a sparky to do work on domestic wiring but who do you go to for VFD’s?

I have an ulterior motive for asking that question.  A friend has just bought a Colchester lathe with a 3 phase motor.  He’s well aware of the benefit a VFD would be but will admit to struggling to fit a 3 pin plug.   He has asked around but cannot find anyone who will do the installation. Any ideas?

 

If you ask nicely I bet Newton Tesla would come up with a package pre-wired so all you have to do is connect to the motor and plug it in. The only out of the ordinary bit then is swapping the motor from star to delta, but if it’s a reasonably modern motor that will only be swapping some links around. No doubt NT will send instructions

[Sonic Escape]

On Sonic Escape Said:

…

I’m going to buy two Delta electronics VFDs. A 2.2kW model and a smaller one of 0.75kW. They have EMI filters. I’m going to share them between a lathe, a mill and a vertical band saw. I’ll add a 3-phase socket to each VFD and connect what I want to use in that moment.

 

Miss the points about not sharing VFDs between motors, and never switching their outputs?  Sonic needs 3 VFDs, each permanently wired to it’s own motor. with no plugs and sockets!

VFDs are wonderful for controlling one motor, but asking them is to do more than that is unwise.   Sharing one between motors is asking for trouble.  More usual in our circumstances to install a rotary converter when plug shareable 3-phase power is required in a workshop rather than prat about with electronics.  Although noisy and inefficient, their having no bells and whistles means they’re too stupid to care about the subtleties that upset VFDs.

Dave

 

[Sonic EscapeParticipant @sonicescape38234]

But I use only one machine at a time. I need two VFDs because of the milling machine. It has two motors. What is wrong with using a plug and socket to connect to a VFD? Even if by mistake I turn the VFD without a load nothing will happen. It is an open loop system in V/Hz mode . And I don’t share the same VFD with two runing motors.

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