Single phase motor switching issue

[Murugesh_89]

Hi,
I am rotating a single phase induction motor as per the wiring diagram below.



I do these things..
1.Motor OFF - By switch off both the solid state relays
2.Forward rotation - SSR1 on and SSR2 off
3. Reverse rotation - SSR1 off and SSR2 on

When i do this these three things repeatedly say ( 10 cycles ) my Solid State Relay 1 (Forward rotation ) gets over heated and damaged. I damaged two relays ( which i connected for forward rotation).

What is the wrong with my wiring?

 

[crutschow]

What is the current and voltage rating of your motor?
What is the rating of your relays?
How fast are you doing this switching?
Is the motor stopped when you go from forward to reverse?

 

[Murugesh_89]

Current and voltage rating of motor is 230V and 2A.
Relay voltage and current rating is 480V and 25A.
Start the motor in forward direction and switch it off after 4 seconds. it will be off for another 4 seconds. then start it to rotate reversely and stop it after 4 seconds. it will be off for another 4 seconds..this cycle continues...
From forward to reverse(30%) or from reverse to forward(70%) in both the cases the motor stops.... but initial cycles it is working after some 5 to 10 cycles it is creating this problem.

 

[crutschow]

So are you applying the reverse power before or after the motor stops?

In any case it's likely the high starting current the motor rquires that is overheating the relays. You may need to use a larger relay or attach them to a better heatsink (or to a heatsink if they don't already have one).

 

[schmitt trigger]

what size is the capacitor, a few uf, I would assume?
Does it have a discharge resistor in parallel?

 

[chuckey]

Have you measured the total current when the motor is running in forward and reverse? Most single phase motors have a run winding which always goes across the mains, the start winding (which has the capacitor in series) has the mains applied one way or the other to reverse the direction of rotation.
Frank

 

[iop95]

Add a series connected RC (220ohm/10W, 2.2microF/630V) across terminals of each SSR.