Power Supply

Internal and External Power Supplies

The MicroLogic trip unit is powered by the current through the internal current transformers (CT).

• The standard protection functions of MicroLogic trip units operate with the internal current supply.

• If the load current is higher than 20% of the rated current In, the internal current supply provides the power supply for the full functioning of the MicroLogic trip unit. This includes:

  • The MicroLogic HMI, display screen and LEDs

  • The metering functions

To provide a power supply to the MicroLogic trip unit when the load is below 20% of the rated current In, and maintain the full functioning of the MicroLogic trip unit, a permanent external 24 Vdc power supply can be used.

External 24 Vdc Power Supply

The 24 Vdc power supply maintains the operation of all functions of the MicroLogic trip unit in all circumstances, even when the circuit breaker is open and not energized.

The 24 Vdc power supply maintains the functions of the MicroLogic trip unit in low load conditions (load below 20%).

Recommendations for use of external 24 Vdc SELV power supplies:

• Use separate 24 Vdc power supplies to supply each MicroLogic trip unit. You can use the same 24 Vdc power supply to supply the ULP modules in several Intelligent Modular Units (IMU).

• Use a separate 24 Vdc power supply to supply the MN or MX voltage releases.

Recommended 24 Vdc Power Supply

The following 24 Vdc power supply is recommended for use with ComPacT NS devices. For more information, refer to the ComPacT NS Catalogue.

Characteristic	AD power supply
Illustration
Overvoltage category defined by IEC 60947-1	Category IV per IEC 62477-1 (Vac model) Category III per IEC 62477-1 (Vdc model) Category III per UL 61010-1
Input supply voltage AC	110–130 Vac 200–240 Vac
Input supply voltage DC	24–30 Vdc 48–60 Vdc 100–125 Vdc
Dielectric withstand	Input/output: 3 kV RMS for 1 minute (110–130 Vac and 200–240 Vac model) 3 kV RMS for 1 minute (110–125 Vdc model) 2 kV RMS for 1 minute (24–30 Vdc and 48–60 Vdc model)
Temperature	70 °C (158 °F)
Output current	1 A
Ripple	200 mV peak-peak
Output voltage setting for line loss compensation	22.8–25.2 Vdc

24 Vdc Backup Battery

If the 24 Vdc power supply is interrupted, a 24 Vdc backup battery can be used to maintain the operation of the MicroLogic trip unit. It is installed in series between the MicroLogic trip unit and the 24 Vdc power supply module.

The 24 Vdc backup battery must have the following characteristics (compatible with the MicroLogic trip unit):

• Output voltage 17–28.8 Vdc

  • Cut-off voltage 17 Vdc (24 Vdc backup battery must have a shutdown output voltage in case of low voltage level)

  • Hysteresis > 3 Vdc (to avoid power-on before the voltage is up to 21 Vdc)

• 24 Vdc backup battery should be able to power an Inrush current of 10 A

Internal Battery

When no other power supply is supplying the MicroLogic trip unit, the internal battery powers the trip cause LEDs.

ULP Module Consumption

The same power supply can be used to supply the ULP modules of several intelligent modular units (IMU).

The following table lists the ULP module consumption: