Long Start, Locked Rotor Protection; Signal Flow Of The Locked Rotor Protection Function; Startup Phase Of A Motor - ABB UMC100.3 Manual

C O N F I G U R I N G T H E M OTO R P R OT E C T I O N F U N C T I O N S

Long Start, Locked Rotor Protection

This function detects a long start situation which is caused from a locked rotor for example. The function creates a trip if the mo-
tor current continuously exceeds a threshold for a configurable period of time. Blocking of a motor can occur due to excessive loa-
ding of the motor or due to process or mechanical jam. The early detection and tripping of the motor protects the driven mechani-
cal system by further damage and the motor from thermal stress. This function can only trigger a trip. Both the maximum allowed
current and the delay time until the trip occurs can be adjusted.
Block diagram:
I/I [%]
e
I>I
locked
Startup Phase
Blocking
Enabled
—

Signal flow of the locked rotor protection function

To adjust the blocking current threshold correctly proceed as follows:
• Take the highest inrush current value during a normal start.
This value is displayed on the UMC100-PAN.
• Add a safety factor depending on how much your start-up load might vary.
• Set the blocking delay to a value that is shorter than the trip time resulting
from the thermal overload trip at the given current.
• This protection function only works during the motor start-up period
• The motor start-up period ends when the motor current drops to 135% of Ie or if the class time (i.e. Class 5 ->
1.5 s, Class 10 -> 3 s , class 20 -> 6 s, class 30 -> 9 s, class 40 -> 12 s) is over.
• The class time begins with the start command
• After the start-up phase the locked rotor protection is done by "high current protection"
LR
threshold
LR delay
Startup time
—

Startup phase of a motor:

If the motor current does not fall below the LR threshold within
the configured LR delay time a locked rotor trip is triggered.
Relevant Parameters:
• Locked Rotor Level
• Locked Rotor Delay
& T
on
t
Locked
Rotor
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