[chbot] VFD with Chocolate fish.

[Richard Jones]

This document explains the different voltages to expect between single
phase vs 3 phase connected rectifiers and explains why you may find no
neutral connection in a 3 phase rectifier.

https://www.electronics-tutorials.ws/power/three-phase-rectification.html

So as Mark inferred, connecting a single phase supply to 2 phases in lieu
of the 3 phase connections should be safe enough once you verify the
capacitor ratings and you are feeling brave.

However, will the motor being driven cope with the reduced supply voltage?

Cheers

Richard

On Wed, Jun 30, 2021 at 7:13 PM Mark Atherton <markaren1 at xtra.co.nz> wrote:

> Wallace,
>
> Have you checked continuity between mains in and the bridge rectifier
> using a meter, or just by inspection ?
>
> Not sure of the rating of the unit you have purchased, but I might also
> expect some kind of power-factor correction before the main reservoir
> caps. Are you 100% sure that the input terminals don't dive off around
> somewhere and then back to the caps ?
>
> -Mark
>
>
> On 30/06/2021 7:08 PM, Mark Atherton wrote:
> > Sounds like the factory modified the product (wrongly) then shipped it
> > without testing it.
> >
> > Three phase inputs (L1, L2, L3) should go the the bridge rectifier via
> > R, S & T.
> >
> > I have a couple of 3 ph VSDs that don't trip with under voltage if you
> > use single phase, and attach phase to L1, and neutral to L2.
> >
> > Before you go any further, what is the voltage rating of the reservoir
> > cap(s) directly after the bridge rectifier ?
> >
> > I would expect at least 385V caps for the 240V model and 620V caps (can
> > you get these ?) for the 3 ph 415V variant.
> >
> > -mark
> >
> >
> >
> > On 30/06/2021 6:04 PM, Marshland Engineering wrote:
> >> I'm stumped with a VFD from Aliexpress. Here it is
> >> https://www.aliexpress.com/item/1005002038502819.htm
> >>
> >> Nothing turn on with power. As a true engineer, off came the cover.
> >> Now I'm
> >> either blind, missing something  completely or its a faulty design.
> >>
> >> It has a 3 phase rectifier in it, + and - go to the HV caps. One of the
> 3
> >> phase input leads is cut off. Looks like a factory job. The other 2
> input
> >> leads are soldered together on the PCB and go to the input live
> >> terminal. I
> >> cannot find any connection on the PCB from the neutral terminal.
> >> Stumped. Now
> >> I did get a complete new PCB when I discovered they sent me a 240V out
> >> instead
> >> of 380V one . It is exactly the same.
> >>
> >> Anyone got a few minutes free tomorrow ? I come loaded with chocolate
> >> fish or
> >> similar.
> >>
> >> Cheers Wallace
> >> 03 3237449
>
>
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