controlling a mains-powered oven

Sep 06, 2015 87 Replies

Arguing that there is parasitic effects is without value unless you can show they have some impact on the issue.

And the AC waveform takes TIME to ramp up the voltage to a point where it is remotely likely to arc. By that point the gap more than prevents any current from flowing. I would guess you are thinking about the distance to interrupt a current which is not what's going on at this point.

Yep, because the timing is not being controlled.

Rick

The fly in the ointment is that SSR's are more susceptible to things like line transients. As to relays, even SSRs may use a reed relay to eliminate voltage drop across the solid state devices. So they aren't as obsolete as you think.

Back in the 70's, one of my favorite and now mostly illegal power switches was a Mercury switch that used a movable piston and a pool of Mercury. Very high reliability, with a small gotcha! A fault big enough to rupture the containment tube could spread Mercury and vapor all over the place. At the time, a fair number were used to control heating elements in the industrial ovens and Mold machines.

You claimed with less definition

"I believe the arc is largely created by inductive loads because of the large voltage spike caused by the large dI/dt, no?"

And you moan about my comment when mains cable often has 100pF per metre capacitance (L or N to E), every connection and cable has its own capacitance and inductance. Some of the magnetic field of the coil of a relay is also in the contacts.

Show that an oven has NO parasitic effects. Especially with the several Amps of I to create a dI (at on or off time).

see

As contacts are known to bounce on relays and switches from 1 to 20ms and you assume it takes ZERO time to separate contacts.

Right a very simple knowledge then.

Paul Carpenter | paul@pcserviceselectronics.co.uk PC Services Raspberry Pi Add-ons Timing Diagram Font For those web sites you hate

Thought this would be very appropriate to uk.d-i-y

Windows 8.1 on PCSpecialist box

Why? Is it full of Raspberry Pi enthusiasts who for some reason can't subscribe to comp.sys.raspberry-pi ?

IIRC there have been updates since.

Windows 8.1 on PCSpecialist box

So you should have had the updates to forced on you to Windows 10 ...

Paul Carpenter | paul@pcserviceselectronics.co.uk PC Services Raspberry Pi Add-ons Timing Diagram Font For those web sites you hate

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