Thread: Need help with electrical issue ...

I'm not a sparky but I do understand electronic circuits.

The phase swap switches are for changing the direction of the motor M1.

The rectifier is to provide DC for the relay coil B1.

The white ceramic things look like fuses to me.

Originally Posted by Vernonv

Hi All,
I recently purchased an old TOS milling machine and am in the process of setting it up. I have stumbled across and electrical issue and I'm hoping some here might be able to assist.

I'm running the mill off a rotary phase converter and everything function correctly except for the main motor (or more correctly, the switchgear associated with the main motor).

Now I have enough electrical/electronics knowledge to be dangerous, but there are a couple of aspects of the setup I'm unsure about :

1. What is the purpose of the switch (circled in red) swapping phases?
2. What is the purpose of the rectifier section (also circled)? That has me baffled as it seems to be feeding DC to the AC/motor.
3. What are those white ceramic things in the attached photo? The are designated as Px in the circuit.

I've attached the full circuit schematic as a pdf.

3. is easiest to answer. These are European fuse-holders. The equivalent of the ceramic fuse-holders to be found in older Australian homes. Only instead of a simple wire to replace, these contain a real ceramic fuse filled with sand to stop the arc, and with a colored spring loaded indicator that you can see through the glass in the cap. If you unscrew the cap of the fuse-holder, you see the fuse. Take it out of the cap. The color code on the indicator tells the amperage. More information is stamped into the bottom metal cap or printed onto the fuse side. If blown, you cannot fix it with a wire, you replace the whole insert.


The other two questions are harder, because you only provide part of the diagram. I have a rough guess:

2. this could be a DC injection brake for motor 1. Switch S2 activates the relay B1 if switch S2 is closed and applies a DC voltage between two phases of the motor. Obviously S1 needs to be open for this, else there will be smoke.

1. the dashed lines on V2 could be where one is supposed to swap one phase, should motor M1 run in reverse. When hooking up such a machine to mains, one has a 50% chance to get rotation direction right. Maybe that is an easy place to swap if one gets it wrong. It does not affect motor 1 though - if motor 1 was a coolant pump its rotation direction would not matter though... but 1.1kW seems too much just for a coolant pump. Can you tell us what motor 2 does?

This is just a rough guess. Would need to know more about the machine and see the remainder of the circuit diagram to be more specific.

Originally Posted by Cliff Rogers

The phase swap switches are for changing the direction of the motor M1.

Doh! ... of course.

Originally Posted by Cliff Rogers

The rectifier is to provide DC for the relay coil B1.

But why is the DC connected across the motor?

Originally Posted by Cliff Rogers

The white ceramic things look like fuses to me.

Odd looking fuses.

Originally Posted by cba_melbourne

3. is easiest to answer. These are European fuse-holders. ...

Thanks for the thorough explanation.

Originally Posted by cba_melbourne

The other two questions are harder, because you only provide part of the diagram.

The complete diagram is attached as a pdf in the first post.

Originally Posted by cba_melbourne

2. this could be a DC injection brake for motor 1.

Ok

Originally Posted by cba_melbourne

1. the dashed lines on V2 could be where one is supposed to swap one phase, should motor M1 run in reverse.

Couldn't see the wood for the trees.

V2 is a reversing switch for M1. I know nothing about milling but I presume you may need to reverse the main milling motor occasionally.
As CBA said they are fuse holders. They screw out and you should be able to get replacement cartridges at an electrical wholesaler.(edit: I'd just replace the lot with circuit breakers though. prices here for replacement fuses )
The B1 relay is an interlock. While the main motor is running, nothing will happen with the rectifier. As soon as B1 drops out 66V DC is applied across two phases to the motor.
The DC braking is only on for the time set on KT1

Originally Posted by Vernonv

The complete diagram is attached as a pdf in the first post.

Ok, I did not see the pdf. Still, there must be more diagrams than just the two pages. Otherwise you may have to follow wire for wire and re-trace how it is really all interconnected.

Re the fuses, here a link to cap sizes and color codes:
http://en.wikipedia.org/wiki/IEC_60269
They should be readily obtainable from Europe, all house fuse boxes up to about the 1970's had them.

Thanks all the for help, it is becoming much clearer now.

Originally Posted by cba_melbourne

Ok, I did not see the pdf. Still, there must be more diagrams than just the two pages.

I'm pretty sure that is the complete schematic.

With the enlightenment I received here I tackled the electrical gremlin again tonight (main motor not getting up to speed and eventually tripping). Found that there was a loose wire on the main switch (which wasn't readily visible) which meant that I was only running off 2 phases. In the process I blew one of those damn ceramic fuses, one of the main ones. Using NCArchers advice I replaced those three main fuses with 3 circuit breakers I had lying around. Also mounted them nicely on some DIN rail.

After effecting all the repairs, it's running like a dream. So thanks again for all those that offered advice.

PS : one thing I noticed is that the motor doesn't seem to brake when switched off, so I might need to investigate that a bit further, but I'm not too worried about it ATM.

Originally Posted by Vernonv

In the process I blew one of those damn ceramic fuses, one of the main ones. Using NCArchers advice I replaced those three main fuses with 3 circuit breakers I had lying around. Also mounted them nicely on some DIN rail.

Ideally the three CB's should be linked so that if one phase trips it takes the others with it to ensure that the motor does not get left running on 2 phases, as this causes them to burn out the windings.

Originally Posted by Vernonv

Hi All,
I recently purchased an old TOS milling machine and am in the process of setting it up. I have stumbled across and electrical issue and I'm hoping some here might be able to assist.

I'm running the mill off a rotary phase converter and everything function correctly except for the main motor (or more correctly, the switchgear associated with the main motor).

Now I have enough electrical/electronics knowledge to be dangerous, but there are a couple of aspects of the setup I'm unsure about :

1. What is the purpose of the switch (circled in red) swapping phases?
2. What is the purpose of the rectifier section (also circled)? That has me baffled as it seems to be feeding DC to the AC/motor.
3. What are those white ceramic things in the attached photo? The are designated as Px in the circuit.

I've attached the full circuit schematic as a pdf.

ADDED BY ADMIN

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Good grief ! I haven't seen bottle fuses for a very long time. They are almost antique.

The Mill I'm restoring/ rebuilding also uses similar bottle fuses.
$18+ each at most places, but RS sell them for less than $3 each (in the size I need)

if you order online, the shipping is often free - so worth a look if you need spare fuses.

HTH
Des