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Playing with an old lathe here and the main contactor cum NVR switch has burnt out.

 

A weird thing I've never seen is the contactor coil has two windings? I've seen motor brake coils with two windings where one winding excites the brake then ms later it gets the full wallop to release but never seen a contactor like it.

 

Contactors are pre 1948 when British Klockner were sold. 

 

1934501573_2021-10-1120_57_01.thumb.png.1f2c0cbb09c1d18bd2194696f22a6290.png

 

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Could be separate pull-in and run windings? But then there would be a spare aux contact to cut the pull-in circuit.

plus not usual on smaller machines, even old ones

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Since you will be replacing the contactor, does it matter that the old one had 2 coils?

 

I don't think I have ever seen a lathe that can run in reverse.  Why?

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Running a lathe in reverse is good for manual boring so you can see the cut on the inside but away from you without leaning over the tool post 

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2 minutes ago, ProDave said:

Since you will be replacing the contactor, does it matter that the old one had 2 coils?

 

I don't think I have ever seen a lathe that can run in reverse.  Why?

 

Just interested more than anything. They're big lumps too. Fully strippable. 415V coils. Burnt to a crisp. Can't access the motor terminal box without moving the lathe. Measured nom 6 Ohm between each phase at the overload. IR was circa 2M Ohm each phase to earth. In a damp old shed!

 

IMG_20211011_173428176.thumb.jpg.1fc7904f30f47b1ddc7ed7cbe2b3bf0d.jpg

 

IMG_20211011_173419848.thumb.jpg.f54902ccaa234f08ab7349073b2f777f.jpg

 

IMG_20211011_171905195.thumb.jpg.b1c7d6f2b7e8bbf55e1b56ed8e19a2d9.jpg

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38 minutes ago, markc said:

Could be separate pull-in and run windings? But then there would be a spare aux contact to cut the pull-in circuit.

plus not usual on smaller machines, even old ones

 

The hold on contact is on 1 & 2 isn't it on that RH contactor? Drops out if the o'load trips or you press stop.

 

Or a power failure.

Edited by Onoff

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2 minutes ago, SteamyTea said:

Run a lathe in reverse for LH thread cutting.

Not when I did my machining, you ran the spindle the same way, just mechanically reversed the feed shaft.

 

Agree on internal boring being a good idea to run the spindle backwards.

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Is there just one contractor doing forward and reverse? There were some odd centre off units that had a push pull action so they did do forward and reverse but would also bounce to momentarily energise the other direction like an insta brake effect

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Although shown diagrammatically as above is it possible that one contactor switches two phases for reverse.

 

My lathe has reverse, but a separate mechanical switch to flip the windings.

 

Run lathe backwards with rear toolpost  or for parting off with upside down tool, stops it digging in.

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12 minutes ago, ProDave said:

Not when I did my machining, you ran the spindle the same way, just mechanically reversed the feed shaft.

 

Not if you use a large tap.

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18 minutes ago, SteamyTea said:

Not if you use a large tap.

And a pair of stilsons as a tap wrench so when it get hold the jaws will release and let go lol

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Two separate contactors for fwd/rev. Then the main contactor set up as an NVR. 

 

I think what I thought was a separate winding on the main contactor is just a secondary little coil to energise the pilot light "P/L". 

 

Then the fwd and reverse contactors have a small set of NC auxiliary contacts. They're just used to break the feed to the other contactors coil.

 

Just going to chuck in 3 modern contactors I think, retain the original overload (unless I can find another). The existing coils are all 415VAC. I'll either use 230 or 48VAC coils and a small control trannie if necessary. The fwd/rev is a proper (you can see it sloshing about) mercury switch. Keeps the grey matter ticking over. 

 

No star / delta on this.....

 

It's being run off a dodgy phase converter. 

 

 

 

 

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Just spent 10 minutes at the lathe owners with the voltmeter. 

 

Turned the phase converter on. Left the lathe off.

 

L1 to L2 - 430V

 

L2 to L3 - 430V

 

L1 to L3 - 0V

 

L1 to earth - 0V

 

L2 to earth (machine body) - 430V 😱

 

L3 to earth - 0V

 

He did say he may have wired it wrong...

 

Didn't go any further as just finished a Marston's Pedigree. 

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46 minutes ago, Onoff said:

Didn't go any further as just finished a Marston's Pedigree.

Do a couple more and it will become very easy to do, once.

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28 minutes ago, SteamyTea said:

Do a couple more and it will become very easy to do, once.

 

More tempting than you know at the moment...

 

😉

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The phase converter in question:

 

1628436152671756034413.thumb.jpg.f3587595d43cc9a5ab7a6a064253c178.jpg

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Get him a proper variable speed drive.

 

Or a single phase motor for the lathe.

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On 12/10/2021 at 16:28, SteamyTea said:

Run a lathe in reverse for LH thread cutting.

also for using a parting off tool attached on back of the saddle 

saves fitting it on every time you want to part off while still having your normal turning tool on the other side of  the saddle

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2 hours ago, ProDave said:

Get him a proper variable speed drive.

 

Or a single phase motor for the lathe.

 

Bit pricey a single to 3-phase vsd for this as it is. The motor I don't believe is dual voltage so doesn't offer the option to run 220v delta.

 

Pity as single phase 220 to three phase 220 are comparatively cheap.

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How does the boost button on a phase converter work anyone? Brings other caps in?

 

The above results suggest I've lost a phase. It won't start on the fwd/rev switch but will get going if you press the boost button. Now I know a 3P motor shouldn't start with just two "real" phases present but will run albeit a bit crap on 2 once it's turning. Wondering if the boost does something odd to start it turning. First thing is to check the voltages properly.

Hoping to have another look this weekend.

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44 minutes ago, Onoff said:

How does the boost button on a phase converter work anyone? Brings other caps in

Bypasses the thermal fuse?

 

 

Edited by SteamyTea

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Boost is higher voltage at same frequency I think. Like a torque assist

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Just been back... sober...


Definitely between one phase to earth I'm getting 430VAC:
 

IMG_20211016_110540562.thumb.jpg.9e3f457ea2994a4a1a5d277e2cbc8665.jpg


Where the phase converter connects to the commando socket:
 

IMG_20211016_110632950.thumb.jpg.97bc3c86b5ec434e999e1b10a62efc50.jpg


JB at the back of the lathe:
 

IMG_20211016_110657010.thumb.jpg.8ae046dc347c6161ed6e9d10a884caa0.jpg


Took the lathe out of the equation and checked again. Same results. 

 

Said he's never changed the lead on the converter. 

 

As much as anything it's a case of redoing terminations, sleeving/marking and tidying as I go. 

 

 

 

 

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Delving into the converter is your next stop. What variety is it, transistorised or rotary?

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