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How do you measure the SCRs on the ATS46, ATS48 and ATS22 soft starters?
ATS22, ATS46 and ATS48
All serial numbers for ATS22, ATS46 and ATS48
Static check on SCRs to test if they are shorted.
Power down the soft starter so that you do not have any mains or control voltage. Follow proper lockout/tagout procedures.
When testing the ATS46 you MUST remove the control board before testing.
This is the square front of the unit that the control terminals plug into and where the keypad connects. There are 4 screws that hold the control board to the power section of the softstart that must be removed.
There are several connections to the back of the control board that must be disconnected. Be sure they are properly marked so they can be reconnected to the correct socket.
Do not pull on the wires themselves as you could break the connection to the plug.
Use a Digital meter (Fluke or equivalent) to measure the resistance between L1 to T1, L2 to T2 and L3 to T3.
Check your resistance in both directions. Red probe on T1 and Black on L1 then flip them and put Red probe on L1 and Black on T1. Repeat for other two phases.
A good reading will be 50K ohms or higher. You should expect to see all three legs with similar resistance readings on all 6 measurements.
Low readings indicate a possible issue with the SCR or shorting contactor (if present).