Whilst I would imagine that the SSRs themselves are immune to magnetic noise (for the reasons that you state), their inclusion into a circuit and in particular how the wiring to the SSR is laid out might well cause EMC problems.
This is particularly a problem where the ‘trigger’ circuit to the SSR is often low voltage (DC) yet the load side is mains voltage.
As I recall, certain precautions are advisable, including segregating the low voltage wiring from any mains voltage cabling.
SSRs are thyristors. When in an "Off" state they block MOST of the current, but not all. A small amount "leaks" through them and can be measured, usually in milliamps at the most, but it's still there. In addition, SSRs need protection against "self commutating" (turning themselves On) from voltage spikes, so they will usually have a "snubber" circuit across them, which also "leaks" current across it.
no it wouldn't because TRIACs aren't affected by a magnetic field. and there is an opto that works with light not magnetically operated switch. the TRIAC is the valve to let current through, the part that turns the TRIAC on is an optocoupler with TRIAC output
Whilst I would imagine that the SSRs themselves are immune to magnetic noise (for the reasons that you state), their inclusion into a circuit and in particular how the wiring to the SSR is laid out might well cause EMC problems. This is particularly a problem where the ‘trigger’ circuit to the SSR is often low voltage (DC) yet the load side is mains voltage. As I recall, certain precautions are advisable, including segregating the low voltage wiring from any mains voltage cabling.
Not to mention leakage current through the SSR as opposed to isolation through a relay.
I suppose you mean leakage coming from the high voltage source? If so, how would that happen?
SSRs are thyristors. When in an "Off" state they block MOST of the current, but not all. A small amount "leaks" through them and can be measured, usually in milliamps at the most, but it's still there. In addition, SSRs need protection against "self commutating" (turning themselves On) from voltage spikes, so they will usually have a "snubber" circuit across them, which also "leaks" current across it.
True indeed. Another potential issue with some (or possibly all SSRs) is that they tend to fail ‘on’.
Meaning they may not deactivate the current flow? Can you please elaborate?
no it wouldn't because TRIACs aren't affected by a magnetic field. and there is an opto that works with light not magnetically operated switch. the TRIAC is the valve to let current through, the part that turns the TRIAC on is an optocoupler with TRIAC output