What are the pros/cons of using a solid state relay vs. coil relay?

SSR is an electronic device, while Coil relay is electro-mech device.
Both have their pros & cons.
The life of SSR is much longer than CR.
Further SSR is a complete ckt, while CR is depend on electro-mech principle.
SSR consume little power, while CR can work with high loads.
Mainly its depend, how you design the machine.

Solid state relay has longer life time compared to coil relay.

This is taken straight from Wikipedia

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SSR Advantages over mechanical relays

Most of the relative advantages of solid state and electromechanical relays are common to all solid-state as against electromechanical devices.

1. SSRs are faster than electromechanical relays; their switching time is dependent on the time needed to power the LED on and off, of the order of microseconds to milliseconds
2. Increased lifetime, particularly if activated many times, as there are no moving parts to wear and no contacts to pit or build up carbon
3. Output resistance remains constant regardless of amount of use
4. Clean, bounceless operation
5. No sparking, allowing use in explosive environments where it is critical that no spark is generated during switching
6. Totally silent operation
7. Inherently smaller than a mechanical relay of similar specification (if desired may have the same "casing" form factor for interchangeability).
8. Much less sensitive to storage and operating environment factors such as mechanical shock, vibration, humidity, and external magnetic fields.

Disadvantages

1. Voltage/current characteristic of semiconductor rather than mechanical contacts:
   • - When closed, higher resistance (generating heat), and increased electrical noise
   • - When open, lower resistance, and reverse leakage current (typically µA range)
   • - Voltage/current characteristic is not linear (not purely resistive), distorting switched waveforms to some extent. An electromechanical relay has the low ohmic (linear) resistance of the associated mechanical switch when activated, and the exceedingly high resistance of the air gap and insulating materials when open.
   • - Some types have polarity-sensitive output circuits. Electromechanical relays are not affected by polarity.

Possibility of spurious switching due to voltage transients (due to much faster switching than mechanical relay) Isolated bias supply required for gate charge circuit Higher transient reverse recovery time (Trr) due to the presence of Body diode Tendency to fail "shorted" on their outputs, while electromechanical relay contacts tend to fail "open".

Solid state relays provide the advantages of almost infinite switching lives, bounce-free operation, immunity to EMI, higher operating speeds, low level control signals, small package size, multi-function integration and silent operation.
These advantages can save the design engineer board space, component count, time and money while improving product life, performance, and reliability.
One negative aspect of an SSR comparing with EMR is that semiconductors are never completely on or off.
In the on-state, substantial resistance is present, which can lead to significant heat generation when current is flowing.
So SSRs must be mounted on heatsinks.
In some applications, on-state voltage drop can cause problems for loads that are sensitive to reduced voltage.

SSRs are super fast than Coil relays

 

SSRs have longer switching life. Much more than1000000 times in most cases depending of semiconducter quality.

 

SSRs are expensive than relays and a challenge when applying to an economical equipment.

 

SSRs are super silent and have no "Ticking" noise as in relays.

 

SSRs do not generate sparks. Its one of the most advantage when it comes to the applications like hazardous or flammable applications.

 

Thanks.

An SSR switches on an AC zero crossing. A mechanical relay switches at an arbitrary moment (spark). SSRs are silent and in my opinion safer and more reliable for AC.

To reduce Marshalling Panel Size, Engineers usually Prefer SSR................................

Heat Generation can be Controlled through Proper HVAC system.

Costly as compared to Hard Disk

SSR requires Semiconductor Protection(FF) fuses in load circuit ,otherwise the SSR will be short circuited .Coil Relay can be used for controlling AC,DC  loads whereas SSR is mostly used for AC control and special SSR required for DC control .

SSR is an electronic device, while Coil relay is electro-mech device. Both have their pros & cons. The life of SSR is much longer than CR

no moving parts so better performace and lifespan