Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect  mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point  to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV  at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform  to 0
volt after 5 periods of    500 HZ  but no overshoot. The relay presents no
arcing.  If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
 The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large  spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

 Michael

Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to
0 volt after 5 periods of 500 HZ but no overshoot. The relay presents
no arcing. If i remove the snubber and make the experiment the best place
to switch is zero crossing but i also see large SHARP spikes up to 500
Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to 0
volt after 5 periods of 500 HZ but no overshoot. The relay presents no
arcing. If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

If your load is inductive, the current lags the voltage by 90 degrees.

Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to
0 volt after 5 periods of 500 HZ but no overshoot. The relay presents
no arcing. If i remove the snubber and make the experiment the best place
to switch is zero crossing but i also see large SHARP spikes up to 500
Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

On Feb 26, 3:00 am, "michael nikolaou"
michaelnikolaou_remove_...@yahoo.com> wrote:
Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect  mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point  to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV  at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform  to 0
volt after 5 periods of    500 HZ  but no overshoot. The relay presents no
arcing.  If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
 The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large  spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

 Michael

Hi, Michael. First off, you should spec a 12V relay that's made to
handle inductive loads (you can see a HP rating). This type of relay
has contacts which open more quickly, and are farther apart when
open. A small standard relay might not even open up far enough to
stop an inductive arc at line voltage.

Next, when using a relay to drive a relay, you have to be aware of the
delay-on-make, which can be several milliseconds, especially for
larger relays. That might help explain some of the curious results
you're getting. Turn-on delay can be affected by wear and aging. It
also varies from unit to unit, even in relays with the same part and
lot number. Trying to get this kind of timing accuracy might be the
wrong way to go.

It might be better to take a look at suppressing the arc, which you've
already started to do. Here's an intuitive way to start. First off,
remember your basic goal: you want the voltage across the contacts to
rise just slowly enough so the contacts can pull away without
sustaining an arc. That's all.

Remove the cover from the driving relay so you can see the contacts.
Next, find the current rating of those contacts, and use Ohm's law to
find a resistor which will result in about half that current.

For example, if you have a 220VAC load, and your relay can handle
10A,:

R = 220V / 5A = 44 ohms

Choose a 47 ohm, 1 watt resistor here (carbon comp is best). Now get
a selection of self-healing AC line-rated capacitors, and switch the
inductive load with the 47 ohm and C snubber directly across the load,
repeating and increasing the cap value until the contact arcing
disappears, or at least is minimized. Without knowing anything about
your 220VAC relay, it sounds like your 0.027uF cap might be on the
small side.

Note that ITW Paktron makes a series of Quencharc snubbers that you
can just plug in, which makes selection a snap. They're one-piece,
epoxy-encapsulated units, and are very easy to use.

http://www.paktron.com/pdf/Quencharc_QRL.pdf

If all else fails, remember that physical distance is also helpful.
Do what you can to place the arcing contact as far away as possible
from sensitive circuitry.

Good luck
Chris

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to 0
volt after 5 periods of 500 HZ but no overshoot. The relay presents no
arcing. If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.

My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the contact
of the driver relay i placed one RC snubber circut (27NF with 100 R
resisitor in series) to help with some spikes that were influencing the low
voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform to 0
volt after 5 periods of 500 HZ but no overshoot. The relay presents no
arcing. If i remove the snubber and make the experiment the best place to
switch is zero crossing but i also see large SHARP spikes up to 500 Volts
Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael


Dont switch off at zero voltage, but at zero current.

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the
peak of the mains voltage .At this point there is smooth decaying
waveform to 0 volt after 5 periods of 500 HZ but no overshoot. The
relay presents no arcing. If i remove the snubber and make the
experiment the best place to switch is zero crossing but i also see large
SHARP spikes up to 500 Volts Peak.

WTF are you talking about, the arc across the driver relay contacts or the
arc across the "large 220 volt AC relay?" It gets reall aggrvating when
you don't make yourself clear...

My question is
The switching with snubber must be made at zero crossing or at the peak
of an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.


Your whole idea is dumb anyway, you're working with relays and pull-in
times that are a substantial fraction of line voltage period and vary with
age and operating conditions. Snubbers are spedc'd around worst case and
not timing. They are only an approximation, the inductance of the "large
220 volt AC relay" is non-linear and may differ by 10:1 between pulled in
and out. And some relays require an arc for contact longevity. You let the
relay manufacturer take care of the switching and just work out a better
12V drive circuit immune to the dV/dt current from that HV ringing,
usually means lower impedance drive.

michael nikolaou wrote:
Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the
peak of the mains voltage .At this point there is smooth decaying
waveform to 0 volt after 5 periods of 500 HZ but no overshoot. The
relay presents no arcing. If i remove the snubber and make the
experiment the best place to switch is zero crossing but i also see large
SHARP spikes up to 500 Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak
of an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael


Dont switch off at zero voltage, but at zero current.
So monitor across a small sense resistor, and wait for
zero across that.

can you be more specific about the sense resistor . My circuit creates 500
micosecond pulse at every 50 hz zero voltage crossing.
At this pulse edge i activate relay considering turn-off / off delay to
calculate the peak voltage so 0 current for my inductive load .
Do you have something different in mind?
"Sjouke Burry" <burrynulnulfour@ppllaanneett.nnlll> wrote in message
news:47c44d7e$0$25500$ba620dc5@text.nova.planet.nl...
michael nikolaou wrote:
Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the
peak of the mains voltage .At this point there is smooth decaying
waveform to 0 volt after 5 periods of 500 HZ but no overshoot. The
relay presents no arcing. If i remove the snubber and make the
experiment the best place to switch is zero crossing but i also see large
SHARP spikes up to 500 Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak
of an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael


Dont switch off at zero voltage, but at zero current.
So monitor across a small sense resistor, and wait for
zero across that.


Just use a comparator IC to test the current, how this fits into

"michael nikolaou" <michaelnikolaou_remove_...@yahoo.com> wrote in message

news:fq0kg4$1n3d$1@ulysses.noc.ntua.gr...





Hi

I have a 12 v relay driving an large 220 volt AC relay . Across the
contact of the driver relay i placed one RC snubber circut (27NF with 100
R resisitor in series) to help with some spikes that were influencing the
low voltage driver circuits.
The driver circuit is able to detect  mains zero crossing and fire the
driver relay at an angle i choose .
From what i read the best point  to switch off the power relay is at zero
crossing . I did that and i show a large spike up to 1 KV  at the relay
contact followed by a decaying 500hz waveform to 0 volts . After some
experimentation the best point came exactly when switching off at the peak
of the mains voltage .At this point there is smooth decaying waveform  to
0 volt after 5 periods of    500 HZ  but no overshoot. The relay presents
no arcing.  If i remove the snubber and make the experiment the best place
to switch is zero crossing but i also see large SHARP spikes up to 500
Volts Peak.
My question is
The switching with snubber must be made at zero crossing or at the peak of
an ac voltage waveform ?
What is the behaviour of the circuit ?.
As i understand any large  spikes can harm the X2 capacitor i'm using so
what is the best operating practise ?.

Any help will be appreciated

Michael

Use a solid state releay and dont worry about it.

Bob- Hide quoted text -

- Show quoted text -

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 ???

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.
[ ... ]