MicroLogic™ 5.0P and 6.0P Electronic Trip Units – Instruction Bulletin PDF
48049-137-05EN

Long-Time Protection

Long-Time Protection Switches

MicroLogic 5.0P
Trip Unit

MicroLogic 6.0P
Trip Unit

Long-time protection protects equipment against overloads.

  • Long-time protection is standard on all trip units.

  • Long-time pickup (Ir) (A) sets the maximum current level based on sensor plug rating (In) which the circuit breaker will carry continuously. If current exceeds this value, circuit breaker will trip after the preset time delay. The long-time pickup (Ir) is adjustable from 0.4–1.0 times the circuit breaker sensor plug rating (In) (D).

  • Long-time delay (tr) (B) sets the length of time that the circuit breaker will carry an overcurrent below the short-time or instantaneous pickup current level before tripping. Two options are available:

    • Standard I2t long-time delay curve. See for I2t long-time delay settings.

    • Idmtl (inverse definite minimum time lag) long-time delay curves vary in slope to enhance selectivity.

Option Description Curve
DT Definite time Constant
SIT Standard inverse time I0.5t
VIT Very inverse time It
EIT Extremely inverse time I2t
HVF High-voltage fuse compatible I4t

  • The overload indicator light (C) indicates that the long-time pickup threshold Ir has been exceeded.

NOTE: MicroLogic trip units are powered from the circuit to always provide fault protection. All other functions (display, metering, communications, etc.) require external power. See MicroLogic Setup for more information.

MicroLogic Trip Unit I2t Long-Time Delay Values

Setting* Long-Time Delay in Seconds*
tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600
tr at 6 x Ir 0.5 1 2 4 8 12 16 20 24
tr at 7.2 x Ir 0.34* 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6

  • For MasterPact™ NT and NW circuit breakers, sensor value (In) can be changed by replacing sensor plug (D) located below the trip unit. For further information, see the instructions packed with the sensor plug replacement kit.

  • Neutral protection is not available when Idmtl protection is selected.

  • The Idmtl selections do not utilize the same thermal imaging feature as the I2t long-time protection function. Both the basic long-time protection and Idmtl EIT are I2t curves, but the different thermal imaging features result in different system performances. For welding applications it is recommended the basic I2t long-time protection be used to ensure expected system performance.

  • Both long-time pickup and long-time delay are located on the field-replaceable adjustable rating plug. To change settings to more precisely match the application, various rating plugs are available. For instructions on replacing the rating plug, see Adjustable Rating Plug Replacement.

  • Long-time protection uses true RMS measurement.

Thermal imaging provides continuous temperature rise status of the wiring, both before and after the device trips. This allows the circuit breaker to respond to a series of overload conditions which could cause conductor overheating, but would go undetected if the long-time circuit was cleared every time the load dropped below the pickup setting or after every tripping event.

NOTE: If checking trip times, wait a minimum of 15 minutes after circuit breaker trips before resetting to allow the thermal imaging to reset completely to zero or use a test kit to inhibit the thermal imaging.

MicroLogic Trip Unit Idmtl Long-Time Delay Values

Option Setting* Long-Time Delay in Seconds Tolerance
DT tr at 1.5 x Ir 0.52 1 2 4 8 12 16 20 24 +0/-20%
tr at 6 x Ir 0.52 1 2 4 8 12 16 20 24 +0/-20%
tr at 7.2 x Ir 0.52 1 2 4 8 12 16 16.6 16.6 +0/-20%
tr at 10 x Ir 0.52 1 2 4 8 12 16 16.6 16.6 +0/-20%
SIT tr at 1.5 x Ir 1.9 3.8 7.6 15.2 30.4 45.5 60.7 75.8 91 +0/-30%
tr at 6 x Ir 0.7 1 2 4 8 12 16 20 24 +0/-20%
tr at 7.2 x Ir 0.7 0.88 1.77 3.54 7.08 10.6 14.16 17.7 21.2 +0/-20%
tr at 10 x Ir 0.7* 0.8 1.43 2.86 5.73 8.59 11.46 14.33 17.19 +0/-20%
VIT tr at 1.5 x Ir 1.9 7.2 14.4 28.8 57.7 86.5 115.4 144.2 173.1 +0/-30%
tr at 6 x Ir 0.7 1 2 4 8 12 16 20 24 +0/-20%
tr at 7.2 x Ir 0.7 0.81 1.63 3.26 6.52 9.8 13.1 16.34 19.61 +0/-20%
tr at 10 x Ir 0.7* 0.75 1.14 2.28 4.57 6.86 9.13 11.42 13.70 +0/-20%
EIT tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600 +0/-30%
tr at 6 x Ir 0.7* 1 2 4 8 12 16 20 24 +0/-20%
tr at 7.2 x Ir 0.7* 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6 +0/-20%
tr at 10 x Ir 0.7* 0.7* 0.7* 1.41 2.82 4.24 5.45 7.06 8.48 +0/-20%
HVF tr at 1.5 x Ir 164.5 329 658 1316 2632 3950 5265 6581 7900 +0/-30%
tr at 6 x Ir 0.7* 1 2 4 8 12 16 20 24 +0/-20%
tr at 7.2 x Ir 0.7* 0.7* 1.1* 1.42 3.85 5.78 7.71 9.64 11.57 +0/-20%
tr at 10 x Ir 0.7* 0.7* 0.7* 0.7* 1.02 1.53 2.04 2.56 3.07 +0/-20%
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