Protection for Motor-Feeders

Presentation

MicroLogic 6 E-M trip units on ComPact NSX circuit breakers:

• Provide protection for direct-on-line motor-feeders (direct-on-line starting is the most widely used type of motor-feeder).

• Integrate the basic protections (overload, short-circuit, and phase unbalance) for the motor-feeder and additional protections and/or specific options for motor applications.

• Allow protection and coordination of the motor-feeder components that comply with the requirements of standard IEC/EN 60947-2 and IEC/EN 60947-4-1. For more information, refer to DOCA0140EN ComPact NSX - Circuit Breakers and Switch-Disconnectors 100–630 A - User Guide.

Description

ComPact NSX circuit breakers equipped with the MicroLogic 6 E-M trip unit can be used to create motor-feeders with two devices.

A ComPact NSX circuit breaker equipped with a MicroLogic 6 E-M trip unit

B Short-circuit protection

C Overload protection

D Ground-fault current protection

E Contactor

F SDTAM Module Option

Operating States

The MicroLogic 6 E-M trip unit considers the application to be operating as soon as the 10% of Ir pickup is crossed in a positive direction by the motor current.

Two operating states are considered:

• Startup state

• Steady state

Startup State

The MicroLogic 6 E-M trip unit considers the application to be in startup state according to the following criteria:

• Start: As soon as the 10% of Ir pickup is crossed in a positive direction by the motor current

• End: As soon as the Id pickup is crossed in a negative direction or at maximum after a td time delay defined as follows:

  • If long-start protection is not activated (factory setting), the Id pickup equals 1.5 x Ir and the td time delay equals 10 s (non-adjustable parameters).

    Exceeding the 10 s time delay does not result in tripping.

  • If long-start protection is activated, the Id pickup equals Ilong and the td time delay equals tlong (adjustable parameters).

    Exceeding the tlong time delay results in long-start protection tripping.

Steady State

The MicroLogic 6 E-M trip unit considers the application to be in steady state according to the following criteria:

• Start: As soon as startup ends

• End: As soon as the 10% of Ir pickup is crossed in a negative direction by the motor current

Operating Diagram

The following diagram shows the two operating states for a motor application:

A ComPact NSX circuit breaker status (green = ON position)

B Contactor status (green = ON position)

C Current in the motor application

Operating states:

D: Startup state

E: Steady state (the active states are shown in green)

Protection Functions

The following figure and table define the protection functions for MicroLogic 6 E-M trip units:

Each function is reviewed in detail on the following pages.

Additional Protection

The MicroLogic 6 E-M trip unit incorporates additional protection functions for motor applications.

The additional protections are activated for startup or steady state or in both cases.

Setting the Protection

Set the protection functions:

• On the MicroLogic trip unit, by using the adjustment dials and the keypad (depending on the protection function and the MicroLogic type).

• With EcoStruxure Power Commission software (password-protected)

• By sending a setting command using the communication network (password-protected)

Reflex Tripping

In addition to the protection functions integrated in the MicroLogic trip units, ComPact NSX circuit breakers have reflex protection. This system breaks very high fault currents by mechanically tripping the device with a “piston” actuated directly by the pressure produced in the circuit breaker from a short-circuit. This piston operates the opening mechanism, resulting in ultra-fast circuit breaker tripping.

SDTAM Module Option

The SDTAM module early tripping function can be used to command contactor opening 400 ms before the calculated circuit breaker tripping in the case of:

• Long-time protection

• Phase unbalance protection

• Motor jam protection

• Underload motor protection

The contactor can be closed again automatically or manually depending on the setting of the SDTAM module. For more information, refer to DOCA0140EN ComPact NSX - Circuit Breakers and Switch-Disconnectors 100–630 A - User Guide.

Example of Using the SDTAM Module

The following figures illustrate operation of the Motor jam protection without the SDTAM module (diagram Ι) and with the SDTAM module (diagram ΙΙ):

1 ComPact NSX circuit breaker status

White: Open; Green: Closed; Black: Tripped

2 Contactor status (SD contact in the contactor coil)

White: Open; Green: Closed

3 Motor current

4 Monitoring by motor jam protection

White: Not active (startup state). Green: Active (steady state)

Analysis of Operation

The following table describes operation without the SDTAM module (diagram Ι).

The following table describes operation with the SDTAM module (diagram ΙΙ).

The SDTAM module can be set to the OFF position: the application is returned to service manually (by deactivating the SDTAM module power supply).