SSR vs Conventional Relay??

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geoff1985

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what is the advantage of SSR vs Conventional Relay and its application?? Thank you
 

If you mean SSR as in solid state relay, the advantages are
-no moving parts
-longer operation. can survive an indefinite number of switches - electromechanical relays tend to wear out eventually due to moving parts
-no sparking. this also leads to longer life
-very fast switching times. Because these relays are controlled by an infrared LED, the switching speed is measured in microseconds.
-they can be much smaller than electromechanical relays
 
geoff1985 said:
what is the advantage of SSR vs Conventional Relay and its application?? Thank you
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SSR have also disadvantages when comparing with normal, mechanical relays ..
One of them is the leakage current, which in some circumstances may, for example, cause a fluoro light to “glow” even if the SSR is OFF ..

:wink:
IanP
 
Plust to IanP I will add that SSR dissipate power, and request adequate heatsink, at full load can be 40W of dissipation. Relay dont have that problem if contacts are adequate for job.

When we sum SSR with heatsink I dont think he is smaller then relay, but this depends on controlling power (current) in circuit. Plus is good to use isolated SSR, we dont want some elctroshocks when heatsink is touched.

When you look better in auditor (back window) you will notice that relay last longer then SSR (if properlz dimensioned and choosed).

SSR can be used if you need frequent On/Off switching, and if you need silence in device operation, or if you need some power-current adjusting (dimming).
 
as mentioned moving parts? what type of material were the most being used as the moving parts of a conventional relay?
 

Special platine and some legure of materials, what can be in some cases company secret.

**broken link removed**

**broken link removed**

I hope that you will no gather gold and platinum from relay contacts. :-D

If you need for switching higher powers use contactors fathers of relays.
There is silenced contactors in market for some higher price.

In this document you will find answer:

http://relays.te.com/appnotes/app_pdfs/13c3236.pdf
 
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Another advantage of SOME SSR's is that they will not switch off until the AC current goes to zero. This can be helpful if you are switching inductive loads as it will eliminate the voltage spike that you would get if you turned off the same load with a mechanical relay when there was current through the load.
 

Worth a look:

Solid-state Relay Topic: SSR Does Not Turn OFF
http://www.omron-ap.com/FAQ/FAQ02155/index.asp



SSR Switching Characteristics
**broken link removed**


Resistive loads


Inductive loads


Random type SSR uses a phototriac coupler to isolate the input from the output




Cautions for Use of SSR
http://pewa.panasonic.com/assets/pcsd/catalog/semi_eng_caussr.pdf




The truth is out there....

;-)

- - - Updated - - -

On the other hand relays have problem with contacts, especially if they are overloaded with current, or is used more than the permissible voltage. Relays usually have determined current for NC and current for NO state of contacts, just as frequency of switching.





General-purpose Relay Topic: Reasons of Relay Burnout
http://www.omron-ap.com/FAQ/FAQ02167/index.asp


Contact Arc Phenomenon
http://relays.te.com/appnotes/app_pdfs/13c3203.pdf
 
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I assume you are referring to AC current switching. One disadvantage to SSR is their on state voltage drop of 1.5v to 1.8v. As current requirements get higher they require large heat sinking. For example 30 amps rms current requires 50 watts of heat sinking.

Another factor is switching split phase 240 vac (U.S. type residential feed). Generally both hot lines should be switched on 240 vac devices for safety reasons. For a double SSR relay this just doubles the heat dissipation requirement.
 

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