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Testing Scrs


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To test the SCRs in the EMS units, there are two simple tests to apply.
  1. Disconnect the inputs and Outputs of the starter, Unplug the white firing loom plugs from the pcb. Measure the resistance of the SCRs on each phase by measuring input to output on each phase. If the resistance is greater than 100K, the SCRs are probably OK.
  2. Connect three 100W lamps to the output of the starter in star connection with the star point floating. The lamps should be rated at the phase - neutral voltage of the incoming three phase. Connect the three phase supply to the input and the control voltage to the control input. Set the starter to start. All lamps should ramp up to full brightness at an equal rate. If one lamp is not as bright, or flickers, there could be an SCR issue, a contact issue or a control pcb issue. Swap the firing loom plugs around. If the problem stays with the same lamp, the problem is with the firing loom or the SCR. If the problem stays with the same socket on the pcb, the problem is with the control pcb.
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