ABB UMC100-FBP Technical Description page 42

Universal Motor Controller
UMC100-FBP
Technical Description
Long Start, Locked Rotor Protection
This function detects a long start situation which is caused from a locked rotor for example. The func-
tion creates a trip if the motor current continuously exceeds a threshold for a configurable period of time.
Blocking of a motor can occur due to excessive loading of the motor or due to process or mechanical
jam. The early detection and tripping of the motor protects the driven mechanical system by further dam-
age 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:
LR
threshold
 Startup phase of a motor: If the motor current does not fall below
Relevant Parameters:
• Locked Rotor Level
• Locked Rotor Delay
UMC100-FBP
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 ther-
mal overload trip at the given current.
LR delay
Startup time
the LR threshold within the configured LR delay time a locked rotor
trip is triggered.
& T
on
t
- 42 -
Locked
Rotor
FieldBusPlug / Issue: 03.2012