Masterpact MTZ2/MTZ3 Device Operation

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

Reset button Position indicator of main contacts Closing spring and ready-to-close indicator

The combination of both indicators gives the device status:

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 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).

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.

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

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