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Step 10In Circuit Testing, negative halve of bridge.
Remember to turn off all power to the equipment and lock out, tag out (LOTO) before testing.
You can test SCRs in a 3 phase bridge without removing them. Below is a typical 3 phase bridge in a power supply. Find the negative and positive bridge output bus bars.
Start by testing 1/2 of the bridge. The three SCRs on the right is the negative halve of the bridge.
Clip the red positive lead of the tester to the negative bridge bus bar (see image notes). Then clip the yellow negative clip to one of the secondary transformer connections. If the bulb remains out, good for you, the bridge is not shorted. Touch a gate wire with the white test wire and test one by one. turn off the SCR by disconnecting the red or yellow wire and move to the next SCR.
If you find any shorts at all, you will need to disconnect all the pig tail connections (cathodes) to isolate each one. Then test each one separately.
You can test SCRs in a 3 phase bridge without removing them. Below is a typical 3 phase bridge in a power supply. Find the negative and positive bridge output bus bars.
Start by testing 1/2 of the bridge. The three SCRs on the right is the negative halve of the bridge.
Clip the red positive lead of the tester to the negative bridge bus bar (see image notes). Then clip the yellow negative clip to one of the secondary transformer connections. If the bulb remains out, good for you, the bridge is not shorted. Touch a gate wire with the white test wire and test one by one. turn off the SCR by disconnecting the red or yellow wire and move to the next SCR.
If you find any shorts at all, you will need to disconnect all the pig tail connections (cathodes) to isolate each one. Then test each one separately.
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