I have a single phase cutting SAW , 3 years old , yesterday i was cutting thick material it stalled as usually happens , but when i turn it off and then On again now it doesn't rotate , it just makes a humming noise .
motor type :
1-AC single phase 220v 2KW motor .
2-it has 6 wires coming out of the motor 2 red 2 black and 2 green wires .
3-Capacitors 200uF 250v and 35v 400v .
steps that i have done :
1- tested capacitors using FLuke , 200uF measures 220uF , and 35uF measures 22uF.
2- tried rotating motor by hand , i runs smoothly and freely ( no bearing problems and such)
3- i disassembled the motor , it is surprisingly very clean from inside , the centrifugal clutch seems OK , the contacts are clean , i wiped them and re-oiled them and continuity test seem OK ( the 2 green wires ) .
Question : and what could be the problem ? is it a shorted winding and how to know exactly
thanks in advance …
EDIT :
As advised by the commenter , i made some tests using an LCR meter ( with 100hz lowest frequency) it appears that the stator coil from black wire 1 to black wire 2 has 30mH inductance . BUT from Red to red which is supposed to be the main Coil there is very high inductance (3000 Henry) and resistance is in the Mega Ohm range.
I donot know if this is an indicator of short coil or open coil maybe the connecting wire is broken ?? does anyone has know how to fix this ?
Best Answer
If the centrifugal switch is OPEN when at rest, that's your problem. It should be CLOSED at rest and OPEN when at 80% speed.
When you stall and try to keep using a single phase capacitor-start motor, it slows down, then the centrifugal switch re-closes, putting the start winding and cap back into the circuit. But that winding is not designed to be used under load, neither is the centrifugal switch. You burned out the switch, maybe the winding insulation too.