Thread: Mars Lathe DC motor conversion.

Hi Ewan,
Just a word of warning, unless they have fixed the manual, SPM and SPL are reversed in some locations.
Just makes things a little more interesting
So if Pd048 doesnt doesnt seem to be working as it should try Pd049

Stuart

Thanks Simon, post printed for future reference!

Thanks Stuart, i'll keep that in mind when i'm setting it up. i have read some of the many threads on the joys of these VFD's, but no doubt i'll run into problems somewhere......

I picked up my stash of motors today, but unfortunately there is one problem....they are all, except the small green 1.5hp one, 2880 rpm! DAMN! Thinking again now though i think i missed one......must be in another pile of junk (Dads got lots of those). So i now have, 2 3hp 2880 rpm, one star only, one star/delta, 2 2hp, 2880 rpm, star/delta, 1 1.5hp 1440rpm star/delta, with an unusual friction drive variable speed gearbox, and a 2900 rpm single phase! I might buy that DC motor you pointed out to me this morning yet Stuart!
IMAG1309 (Large).jpg

Hi Ewan,
Flipping through the thread it looks like you are replacing a 1/2hp 1400rpm single phase motor?
Your DC motor was 1.5hp 4200rpm.

So whats wrong with the 1.5 or 2hp 2800rpm motor?

Stuart

I'm concerned about the torque at lower speeds, although i should have plenty of extra hp to use at the higher rev ranges, once the motor is down at 10hz i'm concerned it just won't have the torque the DC motor did. I guess i'll just wire one up and see.

oh so your first pick would be a 1.5hp 1440rpm? Makes sense

Stuar

Hi Ueee,

There's no way that a 3 phase induction motor can compete with a DC speed for speed HP for HP at lower speeds. Having said that, I'm still impressed by the torque my 3 HP 3 phase has at 10Hz. When used in a 2:1 gearing, there is no way I can stop it with my hand on the spindle.

Well given that you have seen the advantages of DC, you may be a tough customer to VFD but since I have not really played with DC, I'm happy with the VFD arrangement. Can't wait to have it finished!

Busy time of year and the warmer weather don't speed up projects either!

Simon

Cheap controller Finally arrived yesterday eBay Australia: Buy new & used fashion, electronics & home d

Seems to work ok with 1.5 hp cont 3hp peak motor, although need to gradually increase speed or will trip the inbuilt overload protection. If speed is increased gradually everything works fine. Will post pictures etc of lathe, enclosure and tacho shortly.

I had some time to play with some motors and the vfd this arvo. First i took on one of the star/delta 2hp motors......but hang on, they are not star/delta they are star/star star....which i found out is parallel star (thanks google!). The motors have 9 terminals, 6 coils and one star point. You can run them on 440v with 2 coils in series for each arm of the star, or as 2 separate stars on 220v......
Any way, i excitedly wired one of the motors up as per the diagram under the cover (still there!) and turned it on......The motor made a noise like i imagine the LHC would on startup (or maybe a laser gun charging up?), but it was just barely spinning and with no power what so ever. Maybe the motor is burnt out? So i tried the other one....same deal.....I pulled the star point out one of the 3hp motors (its says on the nameplate star/delta 440/220v but the star point was internal????) and tried it....same again. How bout a 3hp on star, motor i know works, should be ok at 220v but with only 1/2 power....nope.

I went back into work pretty #issed off, and started to think, i wonder if the VFD is faulty, surely not? I had noticed some of the settings were not at the factory values listed in the book, but the book is hopeless right? I decided i would reset the VFD (PD13?)

Got home, reset it, put the 2hp motor details back in and what do ya know, she works! Don't know what was set to what, but i wonder if i have a used unit?
So now i just need to adapt the motor to fit the lathe and try it out. Plus Simon seems to have thrown down the gauntlet on control panels so i'd better get designing......

So that got so long winded.....

Hi Ewan,
I'd say your VFD was supplied with the base freq set to 400Hz.
Though the noise wasnt that bad as I recall.

Stuart

Hi Ueee,

I too had a similar experience with my VFD and motor. The very first time I powered it up was straight after I rewired it internally from star to delta. I was a tad nervous to say the least. The motor turned but it was like I had a 1/10 HP motor in a 3 HP package! There was not a lot there. I started to get a bit worried and a little disappointed I also started looking at the settings and wondering which ones to change. First thing I did was reset to factory settings and all was good. I played a little with the V/F curve for curiosity but found little change, but then considering it uses about 1/6 of it's rated power when running with nothing attached to it, I probably wouldn't notice a difference.

Also, the biggest influence on motor noise I found to be the carrier frequency setting.

Thanks for the compliment on the front panel.

Simon

I spent some time this arvo on a new control box, and i pretty well got it done...sort of.

It still needs some graphics to bring it up to Lehmann Eng. standards but that will probably never happen.....
I have it switched just like the DC controller, a left or right rotary switch for Fwd and Rev, pot, e stop, jog fwd and rev and a 3 way coolant switch. I decided to use a 3 way switch for when i get around to a coolant pump so i can have Off, On and on with the main motor.

My biggest issue is: I set the frequency from 8-60 hz. But i want 5hz for the jog. But in setting the low end hz to 8 i can't set the jog any lower than 8? The other is the ramp up and down time for the jog, i have the 1st (lowest 2 PD's for ramp)ramp times set to 4sec up 2 down, but the jog takes maybe 10 sec up and down. I can't seem to find anything in the book about the jog ramp speeds.

Oh, and the 10v power supply on the VFD is not enough to run the tacho, plugged in the voltage drops to 6v which of course plays havoc with the pots output.

IMAG1314 (Large).jpgIMAG1313 (Large).jpg

Hi Ewan
Try
pd007=5
pd042=5
pd020=4
pd021=2
pd073=8


Stuart

Hi Ueee,

I think Stu has it covered. The 4 different ramp up and down times are not explained very well in the book. I didn't realise that the fourth one was for the jog!

Front panel looks great! Looking at the rear, you have put me to shame. I didn't heat shrink all my connections. I thought about it at the time but I didn't have any of the correct size.

As for the 10V supply. It was worth a try, but any voltage drop will be read as a change in speed at V1.

Cheers,

Simon