0614IB1701

Masterpact MTZ2/MTZ3 Device Operation

Masterpact MTZ2/MTZ3 Device Status Indication

The indicators on the front of the device show the following information:

  • Reset button:

    • In: the device is closed or open voluntarily (not tripped)

    • Out: the device has tripped

  • Position indicator of main contacts: Open or Closed.

  • Closing spring and ready-to-close indicator. The state can be one of the following:

    • Discharged (no energy to close the circuit breaker)

    • Charged not ready-to-close

    • Charged ready-to-close

  1. Reset button

  2. Position indicator of main contacts

  3. Closing spring and ready-to-close indicator

The combination of both indicators gives the device status:

Masterpact MTZ2/MTZ3 Device Status Description

Position Indicator of Main Contacts

Closing Spring and Ready-to-Close Indicator

Device Status Description

Device is off (contacts are open) and closing spring is discharged.

Device is off (contacts are open) and closing spring is charged. The device is not ready-to-close because at least one of the following conditions is true:

  • The device has tripped and must be reset.

  • The shunt trip (MX) is energized.

  • The undervoltage release (MN) is not energized.

  • The device is mechanically locked (by using padlock and/or keylock or by using interlocking cables) in the open position.

Device is off (contacts are open) and closing spring is charged.

The device is ready-to-close.

Device is on (contacts are closed) and closing spring is discharged.

Device is on (contacts are closed) and closing spring is charged.

The device is not ready-to-close because it is already closed.

Masterpact MTZ2/MTZ3 Device Auxiliary Switches (OF)

The position of the device main contacts is indicated by auxiliary switches (OF).

Name

Contact Number

Position of Switches and Contacts

Device status

On

Off

Tripped (by Micrologic X control unit)

Position indicator of main contacts

Main contact position

Closed

Open

Open

Reset button position

IN

IN

OUT

Auxiliary switch (OF) position

1–2

Open

Closed

Closed

1–4

Closed

Open

Open

Overcurrent trip switch (SDE) position

1–2

Closed

Closed

Open

1–4

Open

Open

Closed

Masterpact MTZ2/MTZ3 Anti-Pumping Function

Masterpact MTZ devices provide a mechanical anti-pumping function. In the event of maintained opening and closing orders, the standard mechanism blocks the main contacts in the open position. After a trip due to an electrical fault or intentional opening using the manual or electrical controls, the closing order must first be discontinued, then reactivated to close the circuit breaker. This prevents a cycle of closing and opening.

When remote operation features are used, allow at least four seconds for the spring charging motor (MCH) to charge the device closing spring completely before the shunt close (XF) is actuated.

To prevent the device from closing prematurely, the ready-to-close contact (PF) can be connected in series with the shunt close (XF).

Charging the Masterpact MTZ2/MTZ3 Closing Spring

The closing spring must be charged with sufficient energy to close the Masterpact MTZ circuit breaker:

  • Manual charge: Charge the mechanism by pulling the spring charging handle down six times.

  • Automatic charge: If the optional MCH spring charging motor is installed, the spring is automatically charged after closing.

NOTE: For drawout devices the DAE automatic spring-discharge is factory installed as standard, so the closing spring is discharged when the device is moved from the disconnected to the withdrawn position.

Masterpact MTZ Manual Operation with the Spring Charging Handle (MCH)

The following image shows an Open/Close/Open (OCO) cycle for manually charged devices without an spring charging motor (MCH):

Masterpact MTZ Electrical Operation with a Spring Charging Motor (MCH)

The following image shows an Open/Close/Open (OCO) cycle for electrically charged devices using an spring charging motor (MCH):

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