Tuesday, July 23, 2019

Steps to Selecting a Relay

Follow the steps below to select the correct electromechanical (EMRs) or solid state relay (SSRs) for your applications.

1.    Step 1. Identify mounting type:

a.    Panel
b.    DIN Rail
c.    Plug-in
d.    PCB

2.    Step 2. Identify Required Load Voltage Rating & Type:

a.    AC or DC
b.    Determine maximum voltage to be switched






3.    Step 3. Identify Required Load Current Rating:

a.    Calculate Average Load current
b.    Calculate Surge (inrush) current

4.    Step 4. Identify required circuit/switching arrangement:

a.    Number of poles/circuits to be switched
b.    Normally Open, Normally Closed or
c.    Changover switching function

5.    Step 5. Identify Required Control Voltage & Type:

a.    AC or DC
b.    Control Voltage Range

6.    Step 6. Identify Load Type:

a.    Inductive (Random Turn-on SSR)
b.    Resistive (Zero Crossing SSR)

7.    Step 7. Identify Type of SSR Required:

a.    Standard
b.    Special Application:

i.    Phase Angle Control
ii.    Burst Fire Control
iii.    Soft/Start Capability

8.    Step 8. Use above parameters to identify a relay (electromechanical or solid state) matching maximum load voltage, maximum surge current, load type, control voltage, type & mounting requirements.

9.    Step 9. Determine the amount of heat to be dissipated & select suitable thermal management solution.





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