This picture is shown above a common wiring diagram of the insulation monitoring device, normally, the voltmeter 1PV is open, connecting ST1 contacts 5-7,9-11 (1-3,2-4 of ST1) to contact 9-11 of ST2 and into the ground relay KA. When the positive or negative electrode insulation drops to a certain value, the bridge imbalance makes the KA act and sends the signal via the KM (if the positive or negative electrodes have equal insulation resistance to the ground, which is its disadvantage).
At this time, 2PV can be checked to determine which pole insulation drops (when measuring "+", 2-1,6-5 of ST2 to ground; when measuring "-" to ground, 1-4,5-8 of ST 2 is on.
When normal, the 2-1,5-8,9-11 of the bus voltmeter conversion switch ST2 is on and the voltage between positive and negative buses, indicated as 220 V. ) If the positive insulation drops to ground, put ST1 I gear, contacts 1-3,13-14 are on, adjust R3 to bridge balance voltage meter 1PV indicates zero voltage; then put ST1 to II gear, when its contacts 2-4,14-15-are on, the total insulation resistance of the DC system can be read from 1PV .
If the negative ground insulation drops, place ST1 in II, adjust 3R to bridge balance, and then put ST1 to I to read the total ground insulation resistance of the DC system.
If the positive ground, the positive ground voltage is equal to zero. The negative ground indicates 220V, otherwise when the negative ground occurs.
Voltmeter 1PV is used to measure the total insulation resistance of the DC system,it has a resistance scale.
Since there is an artificial connection site in this insulation monitoring device, in order to prevent other relay misuse, the current relay KA is required to have sufficient large resistance value, generally select 30kΩ, and the starting current is 1.4mA.
A signal can be sent when any pole insulation resistance drops to 20 kΩ. Falling to ground insulation and grounding are two cases.
keywords:wiring diagram,DC insulation donitoring device