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Unidrive M Regen Design Guide 155
Issue Number: 4
Output Power (05.003) and Reactive Power (03.001) are the power and VAR's respectively that flow from the supply to the drive. When Reactive
Power (03.001) is positive the phase current flowing from the supply to the drive contains a component that lags the respective phase voltage, and so
the Regen system appears like and inductance connected to the supply and imports VARs. When Reactive Power (03.001) is negative the phase
current flowing from the supply contains a component which leads the respective phase voltage, and so the Regen system appears like a capacitance
connected to the supply and exports VARs.
When the system is enabled it attempts to synchronize to the supply. If the supply has significant distortion then the synchronization process may fail
and cause an over-current condition to be detected. The system will automatically reset the detected over-current condition and continue to attempt to
synchronize. Once the system is synchronized, then if synchronization is subsequently lost, or an over-current condition caused by a supply transient
occurs, or supply loss is detected (i.e. Supply Loss (10.015) = 1), then the action taken is defined by Regen Syncronization Mode (03.004) as given
below. (It should be noted that the over-current condition will only be reset automatically ten times in any 10 s period before an OI ac trip is produced.)
0: Re-synchronize
If supply loss is detected the system will attempt to re-synchronize when the supply loss condition is no longer active. If an over-current trip occurs the
system will attempt to re-synchronize. If Supply Voltage Detection Mode (03.029) = 0 or 2 re-synchronization will only begin if D.c. Bus Voltage
(05.005) has stopped rising or falling. For Supply Voltage Detection Mode (03.029) = 0, this is so the supply voltage can be estimated from the level
of the DC bus voltage. If Supply Voltage Detection Mode (03.029) = 1 rapid re-synchronization is possible because the system does not wait for the
DC bus voltage to stop falling before attempting to re-synchronize.
1: Delayed Trip
The system operates in the same way as "Re-synchronize" mode except that a Line Sync trip is initiated if synchronization takes more than 30 s.
2: Immediate Trip
The system operates in the same way as "Re-synchronize" mode except that a Line Sync trip is initiated if synchronization takes more than 30 s, and
Line Sync trip is produced immediately if supply loss is detected while the system is synchronized.
3: Auto-synchronize
If an over-current condition is detected then this is reset. The system will simulate the supply angle based on the supply conditions before the over-
current condition and restart the system within 10 ms.
If supply loss is detected the system will simulate the supply angle based on the supply conditions before supply loss was detected. This allows the
inverter to remain active during the supply loss period and it is possible for reactive current to flow into the supply in the normal way, but the active
current is held at zero. As the active current is held at zero the DC bus must be held at the required level externally, therefore this mode is only
suitable for an application where an external system connected to the DC terminals and holds the DC voltage at a suitable level. Regen Supply Loss
AC Level (03.023) should be set to a level that is higher than the likely voltage seen at the inverter terminals due to any current being fed into
the supply (e.g. 10 % of nominal supply voltage) or else the system will attempt to synchronize to its own output voltage. If
Supply Loss (10.015)
remains active for more than 2.0 s then an Island.2 trip is initiated. The diagram below shows the timing and minimum voltage envelope for auto-
synchronization. If the required timing and voltage for transient fault ride-through lies within this envelope then the auto-synchronization can be used
to meet the requirements.
03.001 Reactive Power
RO Num ND NC PT FI
VM_POWER kVAr
03.004 Regen Synchronization Mode
RW Txt US
Re-synchronize (0), Delayed Trip (1), Trip (2),
Auto-synchronize (3)
Re-synchronize (0)
8ms
2s
Regen Supply Loss a.c.
Threshold (03.023) x 1.05
A B C
Transient fault ride through envelope
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