"michael nikolaou" wrote in message
...
Thank guys for your replies .Some of them i have to study first

Let me make some things clear about the circuit and values chosen

1. I've measured turn-on , turn-off delay at 3.3 ms for the driver
relay.All
results are
after calculating this delay .So what is see on the scope is at the moment
i'm explaining
2. the arc is across the driver relay .The power board is inside a control
unit box so
i have to leave with small distances and cpu disturbances.Its actually
a
microcontroller
having the problem .Driver relay contact current rating is 5A at 220V
.Power relay coil is rated is 6
watts consumption at 220V.
[ ... ]

From your info', my guesstimate says the big relay has a 8kohm, 4H coil (I'm
working from a UK 50Hz). This means the current running through it will be
nearly in phase with the voltage across it.
Let's say the current is running about 1mS late, then add on the 3.3mS delay
for the relay to pull in and it seems not unreasonable that you need to be
switching ON about 4-5 mS from the sensed 0V Xover to give minimum
transients. This -coincidentally- just happens to be at the peak AC voltage
point.
A different relay may well have bigger inductance and lower resistance,
these would need measuring and the Arrctan thing doing to get a new phase
angle/delay for the current.

If you put say a 10k ohm 2Watt resistor in // with the power relay coil this
will be effective in quickly quenching the relay coil energy. Or better
still, fitting a Varistor will simply clip the transient to whatever it's
rated voltage is.