Electronics > Beginners

Protection for Electronic Load Circuit

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Vovk_Z:
5W ceramic resistors have TCR 10-50 times larger than low-TCR shunt resistors (from my previous post) so they definitely will drift more.
If you need 7 Amps and can't find low-TCR shunt resistors then I'd use two 0.1R ceramics in parallel (0.05R). Because only one will dissipate 4.9 W at that current and will be too hot (about 120-130 C).
If you still need 0.1R then better to use 0.2R or 0.22R in parallel.

David Hess:
A fuse would normally be used in combination with a crowbar circuit to force it to blow.  I would consider using a relay with an active protection circuit.

Jwillis:

--- Quote from: David Hess on February 14, 2020, 02:41:24 am ---A fuse would normally be used in combination with a crowbar circuit to force it to blow.  I would consider using a relay with an active protection circuit.

--- End quote ---

Now that sounds like something that would work . Could you explain further ?

David Hess:

--- Quote from: Jwillis on February 14, 2020, 04:57:20 am ---
--- Quote from: David Hess on February 14, 2020, 02:41:24 am ---A fuse would normally be used in combination with a crowbar circuit to force it to blow.  I would consider using a relay with an active protection circuit.
--- End quote ---

Now that sounds like something that would work . Could you explain further ?
--- End quote ---

It does not really apply to an electronic load where the source may not be able to supply enough current to blow the fuse.  The idea is that with a known source, like a transformer, rectifier, and capacitor for a DC power supply, an SCR immediately after the fuse between power and ground can be activated to force the fuse to blow.  This might be done for instance if an over-voltage condition was detected at the output.

Jwillis:

--- Quote from: David Hess on February 16, 2020, 05:10:18 pm ---
--- Quote from: Jwillis on February 14, 2020, 04:57:20 am ---
--- Quote from: David Hess on February 14, 2020, 02:41:24 am ---A fuse would normally be used in combination with a crowbar circuit to force it to blow.  I would consider using a relay with an active protection circuit.
--- End quote ---

Now that sounds like something that would work . Could you explain further ?
--- End quote ---

It does not really apply to an electronic load where the source may not be able to supply enough current to blow the fuse.  The idea is that with a known source, like a transformer, rectifier, and capacitor for a DC power supply, an SCR immediately after the fuse between power and ground can be activated to force the fuse to blow.  This might be done for instance if an over-voltage condition was detected at the output.

--- End quote ---
   

Hmm sounds complex. What about preset normally closed temperature switches in series. Or Normally open thermal switches in parallel .If any one of them trips it could force a shutdown of the system that has to be manually reset . A warning buzzer could  activate until a reset is done.

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