Solution to open triac when controlling a split phase AC motor

[mana111]

Hi

I have a big problem with controling a 0.15w 220v 50hz split phase AC Motor (Has capacitor between it's two direction lines). i'm using triac bta41 600V to switch on the directions. with triac driver moc3023. the circuit diagram is attached.
the problem is that the triac is opened (short circuit) after stopping one direction and activating the other.
someone told me a solution which is adding a coil & resistor in series with the motor capacitor but i didn't test it because it's not acceptable to the client.

is there another solution?

thanx alot

 

[IanP]

Re: problem with triac

It is common to add a resonant L-C circuit between the motor windings to damp the energy stored by each motor winding’s inductance, avoiding damage to the switches when the transition from one direction to the other occurs. In addition, this resonant L-C circuit helps motor torque performance each time it changes its rotation.

Quoted from:
"Solid-State Control for Bi-Directional Motors"
http://www.analogzone.com/pwrtech_052301.pdf
Take a look at the picture below .. and use it as example on how to protect both tracs ..

Regards,
IanP

 

[mana111]

problem with triac

hi
thanx
but isn't there any other solution
because the customer dont accept it because more than one motor will be attached to the controller and he doesn't want an expansion circuit ( motor L-C) for each motor

 

[IanP]

Re: problem with triac

There is no other solution than some sort of snubber circuit ..
You have to explain this situation to your client ..

Regards,
IanP

 

[mana111]

problem with triac

ok i will try
and thanx for ur effort

 

[Lak]

Re: problem with triac

Brake the motor first (turn on both triac for some msec) before changing dir.
or
install 1 cap in series (at least 1000Vdc (400Vac) to give some resistance
refer to equation on capacitive reactance for the value for each dir.

good luck