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Anybody know about VFDs ?
davidimurray - 10/5/17 at 08:49 PM

I was given a VFD stripped out of some old redundant plant. I thought it might be useful for my CNC mill that has a 20yr old VFD in it now. The VFD is an Altivar 71, and is rated at 2HP. The motor on my mill is only 0.5hp.

My question is if I set all the parameters as per the motor nameplate will it be ok to run a 05hp from a 2hp VFD?

Cheers

Dave

Toys2 - 11/5/17 at 07:33 AM

quote:
Originally posted by davidimurray
I was given a VFD stripped out of some old redundant plant. I thought it might be useful for my CNC mill that has a 20yr old VFD in it now. The VFD is an Altivar 71, and is rated at 2HP. The motor on my mill is only 0.5hp.

My question is if I set all the parameters as per the motor nameplate will it be ok to run a 05hp from a 2hp VFD?

Cheers

Dave


You can use a bigger drive than the motor rating, the typical max ratio is 10:1, what you do need to consider is that your main supply needs to be rated as the the specification for the larger drive, as the inrush to charge the capacitors is still there regardless of motor size

davidimurray - 11/5/17 at 08:56 AM

Thanks for that. Hadn't thought of the inrush current. Just checked the specs below and it looks like it is the same for all the single phase fed drives up to 5hp

Description
Description

Toys2 - 11/5/17 at 09:28 AM

quote:
Originally posted by davidimurray
Thanks for that. Hadn't thought of the inrush current. Just checked the specs below and it looks like it is the same for all the single phase fed drives up to 5hp

Description
Description


That part looks OK

Just to check, what type of motor is presently fitted to your machine? Do you intend to use that motor?

The reason that I ask is that, if it's a single phase motor, then it's not suitable for use with a VSD

The motor requirements for the manual snip-it that you posted is 3 phase 200-240V
In the UK this would typically be a 3 phase motor designed for star/delta with 200/400v on it's nameplate

Post a picture of the motor nameplate if you need help

davidimurray - 11/5/17 at 12:16 PM

it should be a 3 phase motor as it is currently fitted with a VFD.

According to the original manual :

"The spindle drive consists of a frequency convertor unit which converts single phase input power at 50/60Hz to 3 phase power from 6 to 120Hz to drive the main spindle motor. The frequency of the output power is controlled by
a DC voltage of from 0 to 1Ov which is produced by the SPINDLE section on the MAIN PCB, power is also fed
to the main contactor which closes when the drives are on."

I need to take the covers off the machine to get to the nameplate to confirm but hopefully it should be ok.

davidimurray - 11/5/17 at 12:28 PM

Also found the original VFD manual here -

http://www.denfordata.com/bb/download/file.php?id=460

nick205 - 11/5/17 at 03:10 PM

Must be my job, but VFD meant "vacuum fluorescent display" to me

Toys2 - 11/5/17 at 04:43 PM

quote:
Originally posted by davidimurray
Also found the original VFD manual here -

http://www.denfordata.com/bb/download/file.php?id=460


Ah, that's good, It looks like the Altivar will be a good replacement

Sorry I missed the part in your first post, that it's a replacement for an old VSD

Funny - section 1.2 of the manual ... that's what I said!

Let me know if you need anything else, I used to provide technical support for one of the worlds biggest drives manufacturers

[Edited on 11/5/17 by Toys2]

dave r - 11/5/17 at 07:57 PM

i have a few 1/2 horse vfd's going spare..