Voltage Dips, Load Shedding; The Load Shedding Logic Can Be Triggered - 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
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Voltage Dips, Load Shedding

Motors switched off during voltage Dips or power failure can be restarted on power resumption sequentially to prevent simultane-
ous switch-on of the motors and thus prevent another mains failure on the network. The tripping of motors due to undervoltage of
short duration can be bypassed. It is also possible to restart the process on power resumption by sequentially starting the motors
(staggered start).
The Voltage Dip function is available for the starter types DOL (Direct Online Starter) and REV
(Reversing Starter).
When using the voltage dip function take care about the availability of the contactor supply voltage and the
contactor fallback.
Set the check back delay time > the auto restart window to avoid trips before the UMC has switched off the
contactor if the Dip is longer than the auto restart window.
During a voltage dip the UMC inhibits low voltage, low cos phi and low power warnings and errors. Nevertheless set
a sufficient delay time of e.g. min. 0.5 s for these functions to avoid conflicts with the voltage Dip function.
During a voltage dip the supply voltage of the UMC itself must be available!
For special applications where the supply voltage is switched off too you can create an own function block
application using the function block editor and using the function block 'Non Volatile SR'.
This block allows to save its output state over a power cycle.

The load shedding logic can be triggered

a) from the VI15x voltage module. See upper part of the diagram below.
b) from an external voltage monitor signalling the low voltage situation to several devices. See lower part of the diagram below.
No VI15x module is needed in this case.
The following diagram shows both solutions:
UMC100
VI15x
External
Voltage
Monitor
24VDC
—
A low voltage situation can be detected either by the VI15x module or using an external voltage
monitoring relay. In the latter case the low voltage signal has to be wired to all motor controllers
UMC100
DI0-2
L1/L2/L3
UMC100
VI15x
L1/L2/L3
UMC100
DI0-2