Pottery Wheel refurbishment - updating components

[marmiticus]

Hi,
I am updating and servicing an electric pottery wheel.
It's missing what I think is a thermal magnetic circuit breaker and the specs I can find lead me to a now obsolete part by StopCircuit GDU 1U 73 P1
Where do I find an modern swap in part to the same spec and wiring configuration? Most similar devices have only a two wire connection whereas this has 4 wires for some ancillary circuitry.
Its a 240v ac supply, that is running a 1/3hp 1.9amp DC shunt motor (200A 220F) if that helps.
Thanks

 

[Minder]

That appears to be a remote trip type, or at least an alarm contact output.
That is a small motor, you could probabally either use a 2 terminal device or even a fuse.
Do you have any circuit or schematic of the unit to indicate the aux function?
M.

 

[marmiticus]

Hi M,
I don't have a schematic for the aux function so I need to look into it further.
I think this an old wheel and the power switching and overload protection where as separate components. I think a DOL starter or modern manual motor start with built in overload and short circuit protection is what's needed. However, I still have to get to the bottom of the additional cabling out of the missing thermal magnetic trip, as most replacements would only have the in/out connection and no extra cables. It is a DC motor configured in SHUNT so this may have some roll in the extra connections.

 

[Minder]

Yes you can pick up cheap Telemecanique contactors and O/L's on ebay.
You just need to reverse engineer the function on the original O/L.
That IS an old motor if it has a wound field.
In some cases a field loss detector is used to avoid the motor taking off uncontrollably if it loses the field.
M.

 

[duke37]

You need to derive the circuit. A shunt DC motor will take a terrific armature current until the magnetic field has built up.
What controls the motor speed?

 

[Minder]

. A shunt DC motor will take a terrific armature current until the magnetic field has built up.

That is a VERY small motor.!
The O/L is only rated at 1amp.
M.

 

[marmiticus]

You need to derive the circuit. A shunt DC motor will take a terrific armature current until the magnetic field has built up.
What controls the motor speed?

Its an old school radial rheostat

 

[duke37]

It seems strange that it is a shunt motor, I would think that a universal motor would be more likely as in an electric drill. 240W is not small.

Trams used shunt motors, a resistor was used to limit armature current and the shunt field was set to maximum. To speed up the tram, the resistor was reduced, eventually to zero. This would give a medium speed. To go faster, the field was reduced with a resistor. A complicated circuit and quite inefficient.

So, what does the rheostat do? It would be a big rheostat to control 240W.
Any chance of a circuit?

 

[marmiticus]

I'll see what I can do, yet to fully strip the wheel and see whats what.

 

[Minder]

Would it be a Variac style controller?
On this side of the pond, often KB drives or ex T.M. units are used,
You could make a simple 555 based PWM unit with Mosfet output, or even use a Triac dimmer style ceiling fan control followed by a bridge rectifier.
Wound Shunt field motor = 4 connections, Universal motor = 2 connections.
If Universal, the bridge rectifier would not be needed.
M.