Member postings for Andrew Firman

A couple of Centecs advertised on another site. But ad was posted on 1st April......

For Sale: Centec model A and Model B milling machines

Thu 1st Apr '21

Advert ID: 39645

Machines (Large Tooling)
Used (Correct working)

Details:
I bought these 2 machines with the intent to rebuild them, but I have too many other projects to sort out, so they need to go. Both machines are 3ph, and came from a BSC research workshop. both machines have overarms and arbors, the 2B has power feed and a vertical head, and is on the Centec base unit. The 2A has a heavy steel bench for it, made of solid round bar so heavier than the miller. Both machines are bolted to pallets, so could be winched into a trailer or van. These are collection only. this site does not like the pictures I have so email for them.
The 2A is £300 and the 2B £650.

Terms:
Price: Multiple
Collection Only

Contact:
Chris Gunn
Kettering
nn15
UK
01536 482581

Greg, I’m wondering how you solved your P00 220v issue.

I purchased another AT4 sometime ago and have only just got round to checking it.
It was supplied with P00 = 220 and I’m unable to increase above this value. My other two AT4s were supplied I believe with P00 = 380

I’ve queried this with the supplier and received a couple of responses. One states P00 is the input voltage! I’m asking them to reconfirm this and to clarify whether P02, which is Intermediate Voltage in the manual, is supply or output voltage.

What are peoples’ views on the ability of electric cars to tow trailers and caravans? Will it be possible?

Greg,

I’ve not done or found out how to do a factory reset, however a couple of other posters seem to have done so.

I presume your terminals and labelling look identical to those in my photos. There seems to be a difference between an AT1 (220v) and an AT4 (380v).

The only other external identification between an AT1 and an AT4 seems to be the label on the terminal cover. Ie someone could have fitted an AT4 terminal cover to an AT1 which might explain why you can’t set P000 to 380v

I did once try to up load a file with all my parameter settings but couldn’t because it apparently had too many characters. I’ll try again in the next couple of days.

Andrew,

In the manual it states AT4 output phase to phase is 380v

Sorry Greg, Senior moment!

James is correct . P000 on mine is set at 380V..

Greg,

Although the "manual" does not explain I believe P000 is the input voltage which should be left at 220V. That's what mine are set at and both 380 star configured motors run fine.

John, just curious, is your 2.2kw vfd an AT1 or an AT4?

Hi John,

I don’t know what the high ver is . On my 2.2kw AT4 I can adjust to greater than 10 but it is currently set at 10 which was the vfd supplied setting.

I can hear the high pitched noise ( although I don’t find it too annoying - perhaps my hearing has degenerated!).

I’m not an expert but from what I’ve read increasing the carrier freq just to test whether the high pitched sound disappears should not hurt the motor.. However to operate the motor at a high carrier freq for longer periods may be another matter.

You can try increasing P22. The higher it is the less audible the noise is. It’s worth noting that a higher carrier frequency can cause motor to heat up.

I suppose a better way of determining the version would be to compare dates printed on the pcbs.

Reducing P22 from 10 to 6 but it didn’t seem to make an apparent difference to the vibration.

I was reluctant to go above 10 because not knowing the normal operating temp of the test motor. I was a little concerned about the motor casing temperatures I’d measured. Running at 50hz with no load for 10 minutes, the case temp increased from ambient 25c to 46C in 10 minutes. At which time I cut power to the motor and the temp continued to rise to 51C at 15 min before dropping to 44C at 29 mins after commencing the test.

I guess the next step for me is to complete the enclosures, control panels, wiring and fit to my new to me T S M1 and start making chips 😊

Thanks everyone who has contributed knowledge and advice.

James,

I tried using your P00 to P07 parameters but was unable to lower P03 below 4.0 so left all at the manual default settings. I changed P73 to P76 the manual defaults. Everything seems to work as it should except for the vibration when using Vfd#1.

I'm wondering whether we have the same versions of the AT4. Mine is version A03. I purchased mine in March 2019 and am only now getting round to checking them!

As mentioned before one of my AT4s (both setup with identical parameters) seems to cause a pronounced lowish frequency vibration. I've tried to illustrate in the linked videos

Video motor noise using different AT4s

at 50hz

#1Vdf ( noisy one) has a panel indicated current of 2.122 amps and clamp meter measured 1.32, 1.43 and 1.11 amps for W, V and U

#2Vdf has a panel indicated current of 1.985 amps and clamp meter measured 1.44, 1.51 and 1.50 amps for W, V and U

All measured currents are above the motor plate 1.26 amps rating. Should I be concerned about this?

Would the significantly unbalanced outputs currents on #1Vfd be the cause of the vibration? I guess there is no way of balancing the output currents?

Thanks James, very helpful.

Well done Martin (and Dave) 😊.

10K pot working properly and as you say changing back to panel pot results in full hz being achieved at 50% of setting with no further increase if one continues to 100%.

Now I can enjoy the rest of Bank holiday Monday! Though I’ve still to sort rough running on one of the vfds.

Thanks for your time in resolving this conundrum.

That’s interesting Dave because I get half max hz using a 10K pot.

My measured voltage across PE connected to mains earth is 3v. 10 times yours. I have an EMI filter on the mains input so will measure without it.

I tried uploading a MS Word doc of a table I’d prepared in Excel of all the “as supplied” parameters on my AT4s including those not covered by the manual but was unsuccessful because there are apparently too many characters. Can one upload a file?

Sorry James, I somehow missed your post. I would be very grateful if you would post your parameter settings.

As you say blood from a stone.... and to add insult to injury one of the 2 AT4s I have no longer powers my test motor smoothly, so another issue to sort...,.

The pot I’m using.

Many thanks Martin,

The PE terminal is quite easy to see when the board is removed from the case. There is a red wire that connects the terminal and the main board and then through the brass board supports to the fins

The pot is new with a measured resistance of 10.7K . It seems ok but I don’t have any others to swap it with - awaiting a couple from China. I have set P10 and P11 to 2.

I’ve checked the voltage between fins and a mains supply earth connected to the PE terminal and now get a reading of 3v ac down from 85v. Don’t know why it’s not zero but I guess one can live with 3v

I’ve gone through all the “as supplied” parameters (including those not listed on the manual) on one vdf and once I’ve done it for the second one I’ll post a list listing all parameter settings “as supplied” .

Martin, thanks for advice, A couple of queries.

Did your P 73 value also differ from manual? On my vfds supplied set at 61440 manual default 31440.

P75 I need to double check, I’ve recorded a supplied setting of 5560 for one vfd and 1317 for the other. Manual default is 1130 .

When you say no voltage difference between device and mains earth was that with the green PE terminal connected to mains earth?

What is the measured voltage across 5v and COM terminals on your AT4?

James, my P67 supplied setting is 45000. Manual default is 28500. - ostensibly a big difference.

Thanks David. I must admit I can’t find where it says to use a 4k7 pot in my manual but perhaps you are sizing it based on the stated supply 5v voltage and 20ma output plus Ohms law?

That’s interesting Bruce, because the default (factory set) values I found on both my AT4s for p73 and P74 are almost exactly double those shown as the default values in the manual that came with the vfds. I’ll change them tomorrow and see whether the voltage increases from 5 to 10v. Fingers crossed!!
I’d also be interested to know whether your friend noted any ac voltage between the cooling fins and supply earth.

Edited By Andrew Firman on 23/05/2020 22:31:40