On Tue, 26 Feb 2008 19:39:06 +0200, "michael nikolaou"
wrote:

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.
3. Using large value capacitors over 33 nf was causing sometimes latch of
the power relay so i have
value limitation here
4. The capacitors i've chosen are X2 self healing 275VAC. With no ZC control
they are blown
to 0 nf value (some of them) after 10-12 months of operation.
5. I don't have the space or budget to use large sized capacitors rated at
higher voltages or SSR .
The idea was to use ZC to avoid using expensive and large size protection
snubber
So the question is .

Does the relay On/OFF time differs with time .If it's 10% it's not a
problem since again
the arc will not be so high .Since its the current break that causes the
arc i must switch off at Peak of the
ac voltage .This is what my reading confirmed .In this case switching a
resistive load must i change the driver
algorithm ???


However the timing is controlled, yes, that's probably what you need
to do.

The larger relay coil will be rated for power consumption in the
continuous active condition - with the armature closed and inductance
fairly high. The inductance limits the current flow that generates
power loss in the coil, if your phase angle observations are correct.

It's therefor possible that current in the coil is higher than a
guestimate (using the 6W label) might produce. What's the DC
resistance of the bigger coil? What's the actual coil current with the
voltage applied?

Larger currents could account for the control contact arcing and large
voltages that you see with 100R snubber....unless the resistor is open
circuit or intermittent.

RL