As a question, if the load = AC motor, being interrupted by a contactor / relay’s NO contacts
Will the SSR still close, if the AC MOTOR is a open circuit caused by contactor’s NO contacts ?
or the SSR’s need closed circuitry (without any other contactors / relays) between
like a “pull-up” circuitry like an Nchannel MOSFET’s drain ?
does anyone tried to turn on an SSR without load ?
my example:
Thank you.
Greetings,
The precise behavior of any given SSR will depend in large part on its internal construction. Some devices are implemented using FETs in various configurations, others using SCRs/triacs/thyristors, which are somewhat more nuanced devices described at some length in this resource.
Either will in some some regard be “closed” whenever the control input is active however, and due to their leakage current characteristics they are for some purposes “closed” even when they’re “open”.
Note also that in the example diagram shown, a line-to-line short occurs if both devices are activated simultaneously, or without due care for requisite turn-off times, or in event that either experiences a short-circuit failure. Such a configuration would not be advisable for this reason.
Thanks, this SSR is triac based according the datashet.
Making both SSRs turn on, would not happen as they are activated through a small dc relay’s common pole that’s either on contact I or contact II
Such an implementation would be a first-rate example of the “without due care for requisite turn-off times” portion of the preceding response.
The turn-off times of many thyristor-based SSRs is comparable to the transfer times of many small relays. Depending on specifics, the odds of causing a short circuit when the control relay is transferred may be as high as 1 in 2.
