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Technical Bulletin #207
MEGGERING PROCEDURE FOR FULL WAVE UNIT
1. High Resistance Test: Use a megohmmeter (megger) of 500 VDC or greater.
Wiring from the T/R Controller to the feedback terminals must be removed lest the Controller metering circuits be damaged. Any completed primary wiring can remain in place.
The feedback terminals in the low voltage junction box must have a path to ground for this test. Temporarily jumper these feedback terminals to ground. Place the switch in its “HV” position.
Connect the megohmmeter between the high voltage bushing and tank ground. With the high voltage bushing positive and the tank ground negative, the megohmmeter should read less than 3 megohms. With reverse polarity, the megohmmeter should read the voltage divider network connected between the high voltage DC output and the high voltage metering terminal. Refer to your electrical schematic drawing for the value (typically 80 megohms).
A high megohm reading in both directions indicates an open connection; a low reading in both directions indicates a defective rectifier bridge. The bridge cannot be repaired; it must be replaced. Call us at (800) 742-5695 or email us for replacement part information and pricing.
2. Ohmmeter Test of HV Switch: Check the continuity of the HV switch to ground when the switch is in its “GND” position.
This switch is mounted inside the T/R tank. With the switch at “GND”, measure the resistance between the high voltage bushing and tank ground. It should measure only the resistance of the ACR - less than 100 ohms. With the switch at “HV”, the ohmmeter should measure infinity.
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