Reverse switch for single phase, 2 cap motor

Thread Starter

Soldar

Joined Nov 13, 2020
25
Hello all,
I am trying to get my old lathe/mill going again (the old motor seized) and have bought a new dual cap motor with a slight increase in power.
Trouble being, it will need to be reversible due to the lathe needing cw rotation, the mill needs ccw rotation (or the other way around, I forget which).
What sort of switch would make this possible the easiest way, and how do I connect it up please?
 

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MisterBill2

Joined Jan 23, 2018
11,602
I am wondering what that symbol shown in the line connecting V1 and V2 represents. The rest is quite clear. Also,there are two additional drawings that we do not see, which may be for a different voltage, but we have no clues provided.
Certyainly Max is correct, it van be done with a DPDT switch, with one caution, which is that a separate power switch is required and the power must be off while changing directions. Not huge limits, but quite important.
 

MaxHeadRoom

Joined Jul 18, 2013
25,009
That would be really appreciated!
Can you verify/confirm the HP/Wattage of the motor, the telemecanique SW you show is not large enough as far as I can see by the motor plate.
If you cannot locate a DPDT switch of suitable capacity Then the next method would be a simple DPDT relay/contactor, but this has the limitation of automatic reversal in the case of power loss to the coil.
Therefore, for this to be prevented, a reversing contactor should be used where electrical and mechanical interlocks are present and power is removed in the case of power loss.
 

LesJones

Joined Jan 8, 2017
3,702
Hi MisterBill2, The symbol between V1 and V2 is the centrifugal switch. It is initially closed connecting the two capacitors in parallel. The switch contacts open when the motor reaches close to it's rated speed leaving just the run capacitor in series with the auxiliary winding.
The main winding is between terminals U1 an U2 and the auxiliary winding between terminals Z1 and Z2. Changing the straps reverses the polarity of the main winding with respect to the auxiliary winding (In series with the capacitors.)
Les.
 
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MisterBill2

Joined Jan 23, 2018
11,602
OK, I did not look at all of those pictures closely. And thanks for the explanation about the starter switch. I would avoid a relay for exactly the reasons Max gives, and also because it is not a good choice in general, for motor control.
 

MisterBill2

Joined Jan 23, 2018
11,602
The reversing starters that I have used have all been much different from any of the relays that I have used. Yes, a reversing starter would work very well for this application, but it is probably the most expensive choice by a wide margin. A mechanical drum switch would also work very well. And now I wonder what sort of control the previous motor had. That might be a option as well.
 

MaxHeadRoom

Joined Jul 18, 2013
25,009
A contactor is just another form of relay, just built for a dedicated usage.
It all depends if you want the down and dirty way with risks, or the best way with a little more costs.
You can often come upon a deal on Eay for the compact Telemecanique DIN versions etc.
If a different voltage coil is required, often they are available at local electrical suppliers.
 

Thread Starter

Soldar

Joined Nov 13, 2020
25
The reversing starters that I have used have all been much different from any of the relays that I have used. Yes, a reversing starter would work very well for this application, but it is probably the most expensive choice by a wide margin. A mechanical drum switch would also work very well. And now I wonder what sort of control the previous motor had. That might be a option as well.
This is the switch that the original motor had, it had multiple jumper wires between different terminals.
Stupidly I disconnected everything before taking a photo!
 

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MisterBill2

Joined Jan 23, 2018
11,602
OK, that switch may be just what is needed, but now you will need to use a continuity checker to see how it changes connections as it turns. I am guessing it has three positions, one-way, off, other-way. It might have more but hopefully not. And I hope that the terminals all have numbers or letters. That will make discussion much simpler
 

Thread Starter

Soldar

Joined Nov 13, 2020
25
No, I had a close look at the switch, no numbers on the terminals. I will mark them A-L (12 terminals) for discussion and use a multimeter to compile a table of what closes at each switch position.
 

Thread Starter

Soldar

Joined Nov 13, 2020
25
No, I had a close look at the switch, no numbers on the terminals. I will mark them A-L (12 terminals) for discussion and use a multimeter to compile a table of what closes at each switch position.
That was going to take ages. This is simpler: there are 4 "layers" to this switch, each with 2 positions with a "off" position (no contact) in between.
So terminal A to B or C
D to E or F
G to H or I
J to K or L
Does this make any sense?
(Merry Christmas from Australia!)
 

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Thread Starter

Soldar

Joined Nov 13, 2020
25
Ok I may have grossly oversimplified it in my head (correct me if I'm wrong!), but it seems to change direction we only require the straps moved from Z2-U2 and U1-V1 to Z2-U1 and U2-V1.
So... using just 2 layers of the switch we should achieve just this as shown?
There is obviously a section between these 2 switch positions that has no contact. That's fine, I'd never be using lathe/mill at the same time or even within 30 minutes of each other (plenty time enough for the motor to stop).
 

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MisterBill2

Joined Jan 23, 2018
11,602
Yes, that makes quite good sense. But before wiring it all up it would be good to verify that after assembly all of the functions actually work that way. On occasion things do not go right, far better to find an error before all the wires get added.

OK, and I was reluctant to suggest disassembly because some times re-assembly is a challenge. OK, so now which terminal is the common and which terminal is selected with turning in each direction is also understood. There will still need to be a truth table created so that a wiring scheme can be put into words or lines. and the drawing shows it being just exactly what I hoped it would be.
 

Thread Starter

Soldar

Joined Nov 13, 2020
25
Many thanks!
Should I use a 3rd layer of the "switch sandwich" for L1 (active) with a jumper between the 2 other contacts? I'll also wire in an e-stop on L1 for safety, safety wasn't invented back when this machine was made.
 

MisterBill2

Joined Jan 23, 2018
11,602
If adding a mains switch section can be done then that seems like a good idea. But a separate mains switch is also a good plan. Working inside the "back gears" section is no time for the motor to switch on accidentally.
 
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