Auto Restart

Description

The LTMT main unit provides auto restart.

With the auto restart function enabled, the LTMT main unit monitors the instantaneous phase voltage and detects voltage dip conditions. The voltage dip detection shares some parameters with the load shedding function.

Three restart sequences are managed by the function according to the duration of the voltage dip:

• Immediate restart: The motor restarts automatically.

• Delayed restart: The motor restarts automatically after a timeout.

• Manual restart: The motor restarts manually. A Run command is necessary.

All auto restart timers can be adjusted when the LTMT main unit is in its normal operating state. When an auto restart timer is counting at the time it is adjusted, the new duration time does not become effective until the timer expires.

Functional Characteristics

The auto restart function includes the following features:

• Three time delays:

  • Auto Restart Immediate Timeout

  • Auto Restart Delayed Timeout

  • Voltage Dip Restart Timeout

• Five status flags:

  • Voltage Dip Detection: the LTMT main unit is in a dip condition

  • Voltage Dip Occurred: a dip has been detected in the last 4.5 s

  • Auto Restart Immediate Condition

  • Auto Restart Delayed Condition

  • Auto Restart Manual Condition

• Three counting statistics:

  • Auto Restart Immediate Count

  • Auto Restart Delayed Count

  • Auto Restart Manual Count

Parameter Settings

The auto restart function has the following parameters:

Technical Characteristics

The auto restart function has the following characteristics:

Auto Restart Behavior

The auto restart behavior is characterized by the voltage dip duration that is the amount of time passed from the voltage loss until the voltage restoration.

The two possible settings are:

• Immediate restart timeout.

• Delayed restart timeout (with delay defined by Restart Delay Time).

The following diagram shows the auto restart phases:

If the voltage dip duration is less than the immediate restart timeout and if the voltage dip is the second one occurring within 1 s, then the motor will require a delayed restart.

When a delayed restart is active (the delay timer is running):

• The timer is paused for the duration of the dip if a voltage dip occurs.

• The delayed restart is canceled if a start or stop command occurs.

Timing Sequence - Immediate Restart

The following diagram is an example of the timing sequence when an immediate restart occurs:

1 Motor running

2 Voltage dip detected, motor stopped

3 Voltage dip cleared, motor auto restart

Timing Sequence - Delayed Restart

The following diagram is an example of the timing sequence when a delayed restart occurs:

1 Motor running

2 Voltage dip detected, motor stopped

3 Voltage dip cleared, motor auto restart

Timing Sequence - Manual Restart

The following diagram is an example of the timing sequence when a manual restart occurs:

1 Motor running

2 Voltage dip detected, motor stopped

3 Voltage dip cleared, motor auto restart

Bypass Stop DI

If the bypass Stop DI function is enabled and a voltage dip occurs, TeSys Tera system bypasses the stop command received through DI (Local Stop DI and Remote Stop DI).

If there is no voltage dip, the TeSys Tera system will not bypass the stop command, even if the bypass Stop DI is enabled.

DANGER

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH If Bypass Stop function is enabled, use appropriate external interlocks to stop the motor. Configure appropriate voltage dip, restore threshold and nominal voltage. Post installation and configuration, the motor control functionality should be checked before energizing the motor. Failure to follow these instructions will result in death or serious injury.