MicroLogic 2 Electronic Trip Units

Introduction

The MicroLogic 2 electronic trip unit is designed to protect conductors in commercial and industrial electrical distribution.

In 4-pole circuit breakers, neutral protection is set on the MicroLogic trip unit by using a three-position dial:

4P 3D: neutral unprotected
4P 3D + N/2: neutral protection at half the value of the phase pickup, that is, 0.5 x Ir
4P 4D: neutral fully protected at Ir

Description

The adjustment dials and indications are on the front face.

MicroLogic 2.3 3P version

MicroLogic 2.3 4P version
A MicroLogic electronic trip unit setting range B Adjustment dial for the long-time protection pickup Io C Fine-tuning dial for the long-time protection pickup Ir D Adjustment dial for the short-time protection pickup Isd E Value of instantaneous protection pickup Ii	F Test port G Ready LED (green) H Overload pre-alarm LED (orange): 90% Ir I Overload alarm LED (red): 105% Ir J Selection dial for setting the neutral protection (4P only)

The trip unit rating In corresponds to the maximum value of the setting range.

NOTE: The ComPact NSX400K circuit breaker is equipped with a non-interchangeable MicroLogic 2.3 trip unit with no test port.

Setting the Long-Time Protection

The long-time protection pickup Ir is set by using two multi-position dials.

The preset dial allows the pickup to be preset to the value Io (displayed in amperes on the dial).

The maximum preset value (maximum setting on preset dial) equals the trip unit rating value In.
The adjustment dial can be used to fine-tune the pickup Ir (value displayed in multiples of Io on the dial).

Step	Action
1	Set both adjustment dials to maximum (for Io: to the value In (A); for Ir: to 1).
2	Turn the Io adjustment dial higher than the value required. The Ir setting value is: Io setting (A).
3	Turn the fine-tuning dial to specify the value of Ir from 0.9 x Io to Io.
4	The Ir setting value is: Io (A) setting x fine tuning.

The time delay tr for long-time protection cannot be adjusted.

The following table shows the value of the time delay tr for long-time protection (in seconds) according to the overload current (in multiples of Ir):

at 1.5 x Ir	at 6 x Ir	at 7.2 x Ir
tr = 400 s	tr = 16 s	tr = 11 s

Setting the Short-Time Protection

The short-time protection pickup Isd is set by using a multi-position dial.

The setting value is expressed in multiples of Ir.

Step	Action
1	Set the long-time protection first: the setting pickup is Ir.
2	Turn the Isd adjustment dial to the value required. The Isd value is adjustable from 1.5 Ir to 10 Ir.
3	Isd = Isd setting x Ir.

Step

Action

Set the long-time protection first: the setting pickup is Ir.

Turn the Isd adjustment dial to the value required.

The Isd value is adjustable from 1.5 Ir to 10 Ir.

Isd = Isd setting x Ir.

The precision range is +/- 15%.

The time delay tr for short-time protection cannot be adjusted:

Non-trip time: 20 ms
Maximum breaking time: 80 ms.

Setting the Instantaneous Protection

The pickup Ii for instantaneous protection cannot be adjusted.

The following table shows the value of the pickup Ii for instantaneous protection (in amperes) according to the trip unit rating In:

Trip unit rating In (A)	40	100	160	250	400	630
Pickup Ii (A) +/- 15%	600	1500	2400	3000	4800	6930

The time delay for instantaneous protection cannot be adjusted:

Non-trip time: 0 ms
Maximum breaking time: 50 ms.

Setting the Neutral Protection (4P Only)

The neutral selection dial gives a choice of three values for the neutral long-time and short-time protection pickups.

The following table shows the values of the pickup for neutral long-time protection (in multiples of Ir) and neutral short-time protection (in multiples of Isd) according to the dial position:

Dial position	Long-time pickup value for neutral protection	Short-time pickup value for neutral protection
4P 3D	no pickup	no pickup
4P 3D + N/2	Ir/2	Isd/2
4P 4D	Ir	Isd

The time delay for the neutral long-time protection and short-time protection is the same as that for the phases.

Example of Setting the Long-Time Protection

Setting the long-time protection pickup Ir to 63 A on a MicroLogic 2.2 rated In 100 A (see diagram below).

Step		Action
1		Io is positioned on 100 A and Ir on 1 (x Io): factory setting.
2		Io is set to 63 A.
3	–	Adjustment not needed; Ir fine-tuning stays at setting 1
4	–	Ir is set to 63 A x 1.

A precise coordination calculation indicates that the desirable value is Ir = 60 A.

Step		Action
1		Io is positioned at 100 A and Ir at 1 (x Io).
2		Io is set to 63 A.
3		Setting calculation: 60 A = 0.95 x 63 A Fine-tune Ir on setting 0.95.
4	–	Ir is set to 63 A x 0.95 (= 59.9 A).

The actions in steps (2) and (3) on the adjustment dials modify the trip curves as shown:

Example of Setting the Short-Time Protection

Setting the short-time protection pickup Isd to 400 A on a MicroLogic 2.2 rated (In) 100 A on a 50 A feed (see diagram below)

Step		Action
1		The setting pickup Ir for long-time protection is equal to the feeder operating current, that is, Ir = 50 A.
2		Setting calculation: 400 A = 8 x 50 A Position the Isd adjustment dial on setting 8.
3	–	Isd is set to 50 A x 8 (= 400 A).

Step

Action

The setting pickup Ir for long-time protection is equal to the feeder operating current, that is, Ir = 50 A.

Setting calculation:

400 A = 8 x 50 A

Position the Isd adjustment dial on setting 8.

–

Isd is set to 50 A x 8 (= 400 A).

The action in step (2) on the adjustment dial modifies the trip curve as shown: