Lovato PMIB1A230 Insulation Monitoring Relay for IT Networks

Earth-fault watch for isolated (IT) supplies

The PMIB1A230 is an insulation monitoring relay from Lovato Electric for AC IT systems, where the supply is isolated from earth and the first earth fault must be reported before a second one causes a shutdown.

The relay is supplied with 220-240 VAC, occupies 3 modules on a DIN rail and has one output contact: 1 changeover contact SPDT each. A green LED shows power or inhibition, a red LED shows a trip.

Technical specifications

Selecting the relay

Use it on isolated supplies such as some medical, marine and process-control circuits. The intervention threshold is adjustable; compare the table with the insulation level required by the installation standard.

On a normal earthed (TN or TT) supply an earth-leakage relay is the correct device, not this one.

Applications and wiring

Mount the relay on a DIN rail close to the transformer secondary, connect the measuring terminals to the isolated network and wire the changeover contact to an alarm or a shutdown circuit. The relay is normally energised and de-energises at tripping, so a loss of supply also gives an alarm, which is the fail-safe behaviour wanted on safety-related circuits.

Three DIN modules wide, the unit is supplied from 220 to 240 VAC with a power consumption of 3 VA and a dissipation of 1.5 W. The relay contact is rated for 250 VAC with a thermal current of 5 A, an electrical life of 300,000 cycles and a mechanical life of 50,000,000 cycles. Two LEDs show status: green for power on or inhibition and red for tripping.

In an IT system the first earth fault does not interrupt supply, but it removes the safety margin, so the relay’s job is to warn the maintenance team before a second fault can create a dangerous or damaging situation.

Documents and quotation

The figures above are those printed in the manufacturer’s datasheet for PMIB1A230, supplied here as an attached English PDF from the Lovato catalogue. Check the supply voltage and system type, the contact arrangement and the DIN-rail space available against your own drawings first; the manufacturer may update datasheet figures without notice. Related items are listed under controllers & data acquisition. To request PMIB1A230, send the quantity and delivery location with the quotation form; Seven Star LLC is an independent supplier based in Muscat. The datasheet adds relay contact ratings, insulation data and terminal information for wiring in a crowded DIN-rail row.