Member postings for Stuart Bridger

For a suds pump, you can get away with a motor run capacitor across the 3rd phase. No need for a VFD.

Yes soldering does result in alloying between the solder and the surfaces of items being joined.

I have the same issue on my Chipmaster, which shares a common apron I think? From memory the article in MEW implied it was quite a task to resolve? If I test it by winding the chuck manually feeding up to the stop, the pressure builds up and then the feed drops out with a hell of a bang. Under power it just tends to drive the stop along the bed. I am just living without the feature although it would be a nice to have.

Robert, I have to say that I completely agree with your statement, effectively you are just describing what happens when you reduce the frequency from base/rated frequency downwards, whereas I described what happens when you increase frequency upwards to the base frequency. Exactly tthe same.

From the VFD manual
"The rated voltage is used in conjunction with the motor rated frequency (Pr 5.06) to define the voltage to frequency characteristic applied to the motor. The following operating methods selected by Pr 5.14 are used to define the drive frequency to voltage characteristic"

" Fixed boost mode: Fd A linear characteristic is used from 0Hz to rated frequency, and then constant voltage above rated frequency. Low frequency voltage boost as defined by Pr 5.15"

As mentioned previously the "trick" here is to set the base frequency to 29Hz, which changes the voltage /frequency curve to get the best out of the compromise of supplying 230V to a 415V motor

Fror reference see p76 onwards from Commander SK advanced user guide

1. No one has suggested that you don't exceed 29Hz. It is a VFD setting to optimise performance at slower speeds. I can still get the rated 3000 RPM spindle speed out of my chipmaster, albeit with reduced torque. The clue is the V in VFD variable.

2. There is no doubt that this solution is a compromise, but it does work for those who have a single voltage motor and no 3 phase 415v supply available. It was much easier for me to fit a VFD than to replace the motor. It certainly is a viable option that can be considered, IF you don't need the full torque of ex industrial machine.

Edited By Stuart Bridger on 13/01/2020 21:25:36

A bit more research on VFD operation (specifically on the Emerson Commander that I use) shows that the the VFD will modulate output voltage progressively up to the "base frequency" set. Above the base frequency full supply voltage is applied and just the freqeuncy is varied This is where the 29Hz comes in. Setting the base frequency to 29Hz ensures that this voltage/frequency curve is optimised for 230V operation. Agreeing with Robert's post above

Edited By Stuart Bridger on 13/01/2020 17:19:52

The much discussed document from Inverter Drive Supermarket may not be the best worded. What I believe that he is saying that you can get equivalent peformance supplying a 415V motor with 230V up to 29Hz, Efficiency above this frequency starts to drop off. Setting 29Hz as the "base frequency" of the inverter optimises the inverter operation for this situation. Most importantly the full load current must be set to match the motor as it will draw more current for the same power and this needs to be limited ot prevent overheeating the motor. Nowhere in the article does it say don't exceed 29Hz. I run mine up to 50Hz purely so I don't exceed the design rating of the lathe.

This "trick" is ONLY required if you can't rewire your motor for 230V operation. My 1963 motor falls into this category. As mentioned before it does work, so the article can't be complete BS.

Your statement may well be true for industrial use. For hobby use, I have been running a Colchester Chipmaster on 240V with the original 1963 415V motor star connected motor using the 29Hz configuration suggested by Inverter Drive Supermarket for the last 9 years. I have never been lacking in torque/power for the use I put it to. I did try turning 1.25 inch mild steel at 2000RPM witha hefty DOC and feedrate with carbide tooling once. It did slow down the spindle speed a bit, but I was getting seriously hot chips and a stunning surface finish. But that is way beyond my typical usage.

Edited By Stuart Bridger on 13/01/2020 12:19:51

As mentioned above I use the technique highlighted in the article by Colin@Inverter Drive Supermarket.
I don't pretend to fully understand it either but it works! They are a very helpful supplier.
The 29Hz is not the maximum you can set, but will be the value up to where you get full torque with 240V. Above this frequency the motor still runs, but with reduced power. I run mine up to 50Hz and the reduction in power is not significant for hobby use. More significant I beleive is getting the current setting correct.

Edited By Stuart Bridger on 10/01/2020 16:36:01

Depends what you are doing and accuracy required.
If all operations can be completed without removing the stock from the chuck , then no harm in using a 3 jaw

This is a good explanation and the technique I use on my Chipmaster with a 415V star connected motor with a 240V VFD
**LINK**

100% agree. When I worked in industry over 30 years ago, all machine shops were designated eye protection areas. It was mandatory even if just walking down the gangways.

Edited By Stuart Bridger on 09/01/2020 12:14:11

if the holes are small, what about coating with an Epoxy sealant?

I would highly recommend Tripp hearing, not used them for the subject in question though.

This may be of interest, It is the technique I use on my Chipmaster for a VFD conversion.
My lathe has the original 1963 motor which cannot be wired for 240V (or at least not without digging into windings for star point). There is some loss of power, but it is fine for hobby use.

**LINK**

When I was a lad, I grew up on a farm. In those days a bonfire was the standard way of dealing with waste. My father asked me to dispose of a sack from the dairy. On the fire it went. A couple of minutes later there was a bang and an aerosol whizzed past my ear very fast and very close. My dad was mortified and very apologetic that he forgot that he had put it in the rubbish sack. It could have been very nasty.

I would also say tacho generator and aviation related. Evershed were acquired in 1965, so it is older than that.

The part number does show up on google with FBRT1051015 as an associated part, bit no real detail other than hits on aviation part sourcing websites.

A search on ebay for "evershed tacho generator" does bring back some more modern variants

My money would be on the converter not having enough oompf. The "phantom" 3rd phase approach of thesedevices is not ideal.

Also if it as not been run for a while, ltet it warm up for a while before trying the top speeds. It may need the oil needs warming up. When I first got my Chipmaster it wouldn't go a full pelt (3000 rpm).
There is not much that can go wrong in an induction motor, so I expect the motor is OK

Check your minimum and maximum speed settings in the VFD config

I work for a US software company. There is currently a debate going around regarding the terms whitelist and blacklist. These are industry standard terms for inclusion or exclusion of objects. However there is a concern amongst some that the terms are no longer PC. Given how much other work we need to to keep our product ahead of the market, it's certainly not got to the top of the list.