# 2 Capacitor induction motor Humming troubleshooting

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

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 ?

• After you check the clutch switch which sees heavy spike currents then check the inductance of the windings .I hope it is not burnt out Mar 25 '17 at 11:59
• @Autistic , how much the inductance should be ? and shall it be measured by an LCR meter at 60hz ?? Mar 25 '17 at 12:01
• Low values are bad .Inductive reactance determines stall or starting current which may be sat 4 times the run current .The run current will be on the nameplate .If your measured inductance implies some big mains current then there will be a big current while the motor is sitting and humming loudly. Mar 25 '17 at 12:07
• If it "usually happens" (your words) that you're stalling your saw, then it isn't the right tool for the job, and you are seriously abusing it. It isn't at all surprising that one of the motor windings burned out or developed an internal shorted turn from the heating caused by the excessive current. In other words, the next step is to get a bigger saw. Mar 25 '17 at 12:25
• This motor for high torque, you got 2 secondary coil, first with a static capacitor (permanently secondary winding), second is initial starter with switch. Which winding is damaged (or switch)? Secondary permanent winding provide a speed limiting, but all related to load effect, when motor speed is down your per. sec. wind lose phase angle, so go to nearest main winding phase. Mar 31 '17 at 6:38