VFD Question

[Wendelspanswick]

Further on from my post about the 415V/720V motor got me thinking.
Does a 240V input VFD actually only output 120V per phase, giving 240V when measured across any 2 phases?

 

[brewdexta]

You can get 415v output but cost more than the "standard" VFDs used ubiquitously only provide 240 across phases which is why you go for delta connection I believe. I have both, the 415v one is 10HP and is supposed to be a "whole workshop" soluton and is from Direct Drives while I have a small 2HP 240v VFD that predates it to power a mill. Even though it is a "whole workshop" solution, I have a changeover switch to make sure I don't start the lathe and the compressor at the same time. I haven't actually fired it up yet, should be done in the next couple of months in the gap between one lot of buiding work and the next.

 

[brewdexta]

Here's my 415v VFD

 

[Wendelspanswick]

Here's my 415v VFD

I currently use a 240V VFD but I am curious about the actual voltages used.
So am I correct in thinking that your 415V VFD gives out 240V per phase giving 415V when measured across any 2 phases?

 

[brewdexta]

Given I haven't fired it up and measured it I cannot say categorically however that is my impression, and I have talked to them last year and asked similar questions. Here's from their web site

"We are able to supply all types of phase converters from small ¼ HP INVERTER units with a 240 Volts three phase output up to 100 HP DIGITAL CONVERTER SYSTEM giving out 415 Volts three phase with a NEUTRAL line capable of powering a whole workshop full of equipment,"

mine is a 10HP version of the latter

 

[rikrobson]

Here's my 415v VFD

Sorry to be a pedant but thats an inverter

they are similar, but the inverter is a 3 phase supply and the VFD is a motor drive.

Does a 240V input VFD actually only output 120V per phase, giving 240V when measured across any 2 phases?

Its 220V between Phases with most of the chinese ones available. There is no neutral so you should not be measuring phase to neutral.

 

[MattF]

Sorry to be a pedant....

You say that as if it's an uncommon occurence on here.

 

[brewdexta]

Sorry to be a pedant but thats an inverter

they are similar, but the inverter is a 3 phase supply and the VFD is a motor drive.

Sorry, yes your correct, its a PWM inverter. That's not pedantry, its important if somebody else wants to buy something similar

 

[Wedg1e]

I have a 415v VFD driving my lathe and mill (not at the same time, although it probably could)... it is 415V (roughly) between any pair of wires.

 

[piman]

Hello Rik,

terminology, stripped to it's bare bones an inverter changes D.C. to A.C. . One use is to convert the D.C. cross channel link with France back to A.C. for the grid.

Alec

 

[rikrobson]

The digital ones usually convert to do and invert back to ac

 

[daleyd]

As an aside "inverter" is more often than not used in industry to describe a vfd. Variator is another term sometimes used, seen it a lot in French machinery so assume it is French in origin but it seems to have stuck in some places over here.

 

[Luke]

240V AC in, a DC bus voltage of about 340 V DC, and a PWM output pretending to be 240V AC out.