240/460 motor on RPC "Cogging" & shuttering terribly at start up ENCO 13S lathe

US-Choppers · Apr 15, 2021

240/460 motor on RPC "Cogging" & shuttering terribly at start up ENCO 13S lathe

Hi all,

I thought I would reach out to find some of you who are more electrically talented than I..... I have several machines in the shop that I run from a RPC - all of them have run flawlessly. I just brought in a really nice EMCO 13s manual lathe that I tested on site before purchasing - it was hooked up at 460 and ran like a dream. Its plate shows it as a multi voltage unit 240/400/460. I figured I would swap it over to 240 and be done. It has a real easy terminal w jumpers that are self explanatory and the manual shows the proper hookups. I did this according to the diagram I will post w my other data plates- so you can see what I have.

The problem: At start up there is incredible "cogging" for lack of a better term- the spindle shakes back and forth and it sounds like gears are being torn to pieces- I can get it to go smoothly after about 2-3 seconds - but obviously dont want to destroy this cherry lathe because of whatever issue is causing this.

It seems its in the start up circuit- Im wondering if maybe I dont have enough power in the RPC (one of the data sheets shows motor rating as 4/3- I cant imagine its a 4hp w 3hp drive?)... or perhaps I am missing something else that needs attention?

Thanks in advance for your help and input!
Best,
Rick

US-Choppers · Apr 15, 2021

oops! better pics......

johansen · Apr 15, 2021

i think the motor is connected wrong, or you have an open circuit and the motor is single phased.

if you turn the spindle in either direction as fast as you can by hand.. then start the lathe, does it continue running in that direction?

if so this will confirm the motor is single phased.

its a pretty common error to connect a 9 wire motor for low voltage with one of the phases anti-parallel.

SomeoneSomewhere · Apr 15, 2021

Yeah, that behaviour is pretty common for a motor with one winding reversed. I think this is likely to be a Euro-style 6-wire motor from the nameplate.

jim rozen · Apr 15, 2021

One issue to look at is: if the machine has contactors in the control circuitry, be sure those are on the utility power legs. Also changing to the lower voltage, you may need to change out motor starter components such as heaters.

woodchuckNJ · Apr 15, 2021

Just in case anyone cares, this is not an ENCO lathe, it says EMCO which would be a higher quality lathe.

also that is not a single phase motor its 3ph.

And it says it's a 10 amp motor, your phase converter is way too underpowered to start the motor

US-Choppers · Apr 15, 2021

johansen said:
i think the motor is connected wrong, or you have an open circuit and the motor is single phased.

if you turn the spindle in either direction as fast as you can by hand.. then start the lathe, does it continue running in that direction?

if so this will confirm the motor is single phased.

its a pretty common error to connect a 9 wire motor for low voltage with one of the phases anti-parallel.

Hi and thanks, on this lathe, I never dipped into the motor itself- just the front panel w the terminal strip that has jumpers to step up or down on... the machine was bought new and never altered - so I assumed they got it right at the factory... however I will follow some of the leads around and double check as well as your idea on bump starting it and follow up w a response. Here is a pic of the terminal strip and the connections to change voltages from the manual...

US-Choppers · Apr 15, 2021

Since we ran it at 460 at the PO facility and it ran flawless and designed and prewired to run at the 3 voltages < I am thinking it may be more simple? Ie - at the lower voltage maybe it is drawing more amps than my rotary is putting out???? Also one other oddity I noticed was that turned on w no load (rotary running w main power switch on at lathe, but no load) Im reading 280V at the terminals, with spindle under power Im reading back to 250V at the terminals.... is the 280V a bit to high (+16%)????? The manual states +-10 max voltage fluctuation?
View attachment 318948

US-Choppers · Apr 15, 2021

Ha! Yes you are right! I forgot about Enco - yes its German "EMCO"- thank you!

Im looking at the RPC plate - sorry about the pictures- Im trying everything to try to get them to show clearly.

RPC shows:
Amps No Load=3 FLA=15
Min single HP= 1.2 Max Single HP= 3 Total Max HP=7
Max starting KVA =13

Lathe shows:
Amps @230 = 10A (I dont know what amps required for startup- but RPC shows up to 15 under load (FLA=15?))-if MAx starting KVA for RPC is 13 then the RPC should be able to carry 32Amps at 3ph 230 ...is that correct?)

Power w 40%D.C. (hp) = 4,3 (I dont know what the 3 is?) If my RPC max single HP is 3 and my spindle is 4hp.... :scratchchin:

Connection Load (KvA) = 3.0

Max voltage Fluctuation % = +6/-10 (no load/powered on Im reading 280V)-(spindle on 250V)

US-Choppers · Apr 15, 2021

I probably should have posted the above data in my first picture instead of the pictures- its a more concise view of the set-up.

Can anyone interpret the RPC output to the lathe requirements at startup? Im a bit green w electrical (actually I hate it..)....

Im leaning towards WoodChucksNJ comments - is my RPC not enough for startup???

Thanks everyone for your help! Love this community!

JST · Apr 15, 2021

Check wiring to see which wire carries the controls, as the other poster suggested. Should NOT be the "generated leg".

It is VERY unlikely that you could get the thing to run OK if you had a reversed coil. "Wiring errors are forever", they do not change and let the motor run OK unless you change them.

But having controls on the generated leg does that, the voltage drops due to the 5x heavier load*, and the contactors "may not work right"..... they will close, then drop out, then close again, etc...... It is like a doorbell buzzer, only slower.

Your RPC says 3 HP single motor, and your motor appears to be that (10A). Might be slightly more current, but it should be OK per the specs. (reality can vary, depending on the exact motor).

* Motors draw many times their full load current when they are started. The RPC should be OK with that, but you do need to be sure the controls stay powered.

Keyepitts · Apr 15, 2021

US-Choppers said:
Hi and thanks, on this lathe, I never dipped into the motor itself- just the front panel w the terminal strip that has jumpers to step up or down on... the machine was bought new and never altered - so I assumed they got it right at the factory... however I will follow some of the leads around and double check as well as your idea on bump starting it and follow up w a response. Here is a pic of the terminal strip and the connections to change voltages from the manual...
View attachment 318947

If the lathe was connected and running okay at 460V originally, and now you are trying to run it on 230V, you probably (almost certainly) have to change the connections in the motor(s) pecker-head. If you've only changed the connections in the control panel, this probably (in all the cases I've seen) only changes the voltage for the control transformer. Check the motors wiring connections.

US-Choppers · Apr 15, 2021

Keyepitts said:
If the lathe was connected and running okay at 460V originally, and now you are trying to run it on 230V, you probably (almost certainly) have to change the connections in the motor(s) pecker-head. If you've only changed the connections in the control panel, this probably (in all the cases I've seen) only changes the voltage for the control transformer. Check the motors wiring connections.

Thanks guys, Im leaning toward the RPC... the contacts are shuttering and shaking when I power up - Im going to put a new larger breaker in my panel and hard wire straight in - I will post back w results if it works....

Again- many thanks - awesome forum members! Also I have the full manual and electric schems for this machine- will post in "manuals" section for those that need help in future...

JST · Apr 15, 2021

All you may need to do is just change the input wires around so that the controls are across the two wires that are "pass-through" and come straight through the RPC (the RPC ADDS a wire to the two already present.

Controls in a machine are normally powered by a transformer that is connected across two of the three wires coming in (for 3 phase). If either of those wires is connected to the "generated leg" that the RPC adds, you can get that "chattering" problem.

Maybe this is what your post meant, I may not have understood you correctly.

I do not know why you would need a larger breaker, unless the existing one is not rated for the load.

US-Choppers · Apr 16, 2021

Im an electrical idiot - but the way you explained this makes total sense- thank you.

Ended up solving it today - we lacked power from the RPC ... seemed to spec pretty close but just not enough... by a narrow margin... :ill:

US-Choppers · Apr 16, 2021

To wrap up this - we solved the riddle finally. Its a long story on why my panel was set up the way it was- but at the end of the day, the "Cogging" problem was due to a lack of punch. The RPC wasn't enough by a small margin to start the lathe... so we ended up reconfiguring the panel a bit and dropped 3 new outlets combining my single phase needs w 3 phase needs .... plugged all the equipment in and everything is running beautifully!

So I guess it's like Tim the Tool Man Taylor says... "more power!" ...."oooh-oooh-ahhh-ahhhh-ahhh!"

Reminds me of the first lesson in mechanics... if the car doesnt run, check to make sure there is gas first!

So many thanks to all of you- this is a great community, really pumped that we can share in a time where everyone seems to be just concerned w/ themselves.

woodchuckNJ · Apr 16, 2021

US-Choppers said:
To wrap up this - we solved the riddle finally. Its a long story on why my panel was set up the way it was- but at the end of the day, the "Cogging" problem was due to a lack of punch. The RPC wasn't enough by a small margin to start the lathe... so we ended up reconfiguring the panel a bit and dropped 3 new outlets combining my single phase needs w 3 phase needs .... plugged all the equipment in and everything is running beautifully!

So I guess it's like Tim the Tool Man Taylor says... "more power!" ...."oooh-oooh-ahhh-ahhhh-ahhh!"

Reminds me of the first lesson in mechanics... if the car doesnt run, check to make sure there is gas first!

So many thanks to all of you- this is a great community, really pumped that we can share in a time where everyone seems to be just concerned w/ themselves.

that makes no sense unless you have 3phase to the building.

3 outlets do not provide 3 phase power unless you have 3phase to begin with.

yes the RPC did not have enough to start that motor. not sure how it's working w/out increasing the RPC unless you also had 3phase in house.

240/460 motor on RPC "Cogging" & shuttering terribly at start up ENCO 13S lathe

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