trying to understand 3 phase motor/capacitor installation

[qaz]

I'm a qualified mechanic but always tackled small electrical jobs without incident. wonder if i can get some advice re a 60's potters wheel.

it consists of :
-a 220-250 volt 3 phase, c/s 50, motor
-an largish oval capacitor [with a resistor between the 2 contacts] some distance away from motor. A 2 core cable runs from the switch box directly to the capacitor.
-a switch box on outside with 2 buttons, one for on and the other i assume is reset or off.

when switched on it runs extremely slowly for 10 seconds then stops, if you wait for a minute and press what i assume is the reset button, it will start again.

during the 10 seconds it runs you can stop it with one finger at which point it reverses direction.

any help in understanding this installation and why its not working would be much appreciated
m

 

[westward10]

A few pics would help especially the motor rating plate.

 

[Pete999]

Are you sure it's a 3 phase motor, from your description it sound like a single phase job can't be sure though without a pic of the rating plate.

 

[qaz]

here you are
thanks

 

[westward10]

Where do the wires from the capacitor go to.

 

[qaz]

directly into the switch box , no where else

 

[westward10]

Is it running from a single phase supply by any chance. Be interesting to see inside the box if you can take a pic with the power OFF.

 

[telectrix]

i think that's a 3 phase motor. 415V in star, 230V in delta

 

[qaz]

yes we are 240 volts. what does 415V in star mean , pls
will get pic today

 

[Pete999]

i think that's a 3 phase motor. 415V in star, 230V in delta

Agree just read the rating plate OP never mentioned the 380 Volt bit

 

[Pete999]

Is it running from a single phase supply by any chance. Be interesting to see inside the box if you can take a pic with the power OFF.

3/4 HP 0n 3 Phase does sound OTT Like Westward said a pic of the inside of the box, or better still a pic of the motor connections. BUT MAKE SURE THE MOTOR IS ISOLATED PRIOR TO TAKING ANY COVERS OFF
If it is SP then the symptoms suggest either a failed start or run capacitor, or a faulty Centrifugal switch, may need to call a Sparky who is familiar with Motors and the associated control gear.

 

[westward10]

yes we are 240 volts. what does 415V in star mean , pls
will get pic today

It means it will run with 240v in delta connection and 415v in star connection but both supplies need to be three phase. It is possible someone has fitted the capacitor in an attempt to make it run from 240v single phase, possibly.

 

[qaz]

if u still need pic of motor connection just ask. im not familiar with short versions of terms, if u all mind would use whole words if poss,.
thanx

 

[qaz]

It means it will run with 240v in delta connection and 415v in star connection but both supplies need to be three phase. It is possible someone has fitted the capacitor in an attempt to make it run from 240v single phase, possibly.

thanx for clarification . previous owner said that it just stopped working one day

 

[Pete999]

It means it will run with 240v in delta connection and 415v in star connection but both supplies need to be three phase. It is possible someone has fitted the capacitor in an attempt to make it run from 240v single phase, possibly.

Either way get a pro to help.