Phase Loss Protection (Current); Phase Imbalance Protection (Current); Signalflow Of The Phase Imbalance Function - ABB UMC100.3 Manual

U M C 1 0 0 . 3 U N I V E R S A L M O T O R C O N T R O L L E R T E C H N I C A L D E S C R I P T I O N
4 4

Phase Loss Protection (Current)

This function protects motors against the extreme situation where a complete phase is lost. An undetected phase loss can cause
motor damage because of the sudden rise of current in the two remaining phases. Thus the thermal overload protection performs an
accelerated trip during phase loss. This function is based on the motor current and detects a phase loss while the motor is running.
The following table shows the tripping times in case of phase loss for the different trip classes.
Trip class
Tripping time [s]
Relevant Parameters:
• Phase Loss Protection

Phase Imbalance Protection (Current)

The phase imbalance protection protects the motor against a smaller imbalance between the different phases.
The phase imbalance trip level must be carefully adjusted to protect the motor windings against overheating.
Take care of rules or guidelines possibly provided by the motor manufacturer.
Function:
The current imbalance function signals a warning if the ratio between the lowest and the highest phase current in percent is above
the configured warn level.
• Formula: Phase imbalance = 100*(1 - I
The current imbalance function signals a fault if the ratio between the lowest and the highest phase current is above the
configured trip level. The trip delay depends on the trip class setting and is shown in the table below. This function is only active if
the average current in the three phases is above > 25% of the nominal current I
might be signalled instead.
Block diagram:
Imb >
Warning Level
I
123
Imbalance
Detection
Imb >
Trip Level
Phase loss enable
—

Signalflow of the phase imbalance function

Trip class
T
D
Relevant Parameters:
• Curr I Trip Level
mb
5
1.5
/ I )
min max
T = 2...12.5 s
&
D
T = 2...12.5 s
&
D
5
2
• Curr Imb Warn Level
10 20
3 6
. In case of extreme imbalance value a phase loss
e
Imbalance
Warning
Imbalance
Trip
10 20
3.5 6.5
30 40
9 12
30 40
9.5 12.5