Copyright 2010 - Microener
2.2.3.2 – F51LR – Locked Rotor Protection (Rotor jam)
At motor starting this function is disabled for the set time “ 2tSt “ : when this time has elapsed, if
current exceeds the set level “ ILR ”, the relay trips with a delay of “ tLR ” sec.
- Current level :
ILR = (1-5)Im, step 0.1Im. lf ILR = DIS. the function is disactivated.
- Trip Time delay :
tLR = (1-25)s, step 1s
- Inhibition time of the locked rotor function:
2tSt
tSt = (1-120)s, step 1s = motor start-up time
2.2.3.2 - F46 - Current Unbalance (Negative Sequence Current) protection (See curve § 20)
Besides its contribution to the thermal image algorithm, current unbalance also controls another
inverse time element
-Minimum Negative Sequence current operation level
Is> = (0.1-0.8)Im, step 0.1lm. lf ls> = DIS. the function is disactivated.
- Time current curve
tIs> = (1-8)s, step 1s
Actual trip time delay is given by:
“ Is ” is the actual Negative Sequence Current
2.2.3.4 – F47 – Single Phasing
When the relay detects the loss of the current of one phase while the currents of the other two
phases are present, the Single Phasing element “ 1 “ is tripped with a fixed 3 sec. time delay.
2.2.3.5 - F37 - No-Load Running protection
This function performs the protection against no-load running: it is activated by motor under
current.
- Under current level
I< = (0.15-1)Im, step 0,01Im. lf I< = DIS. the function is disactivated.
When current is below 0.1lm in all phases the function is activated.
- Trip time delay = 3 sec.
Im)Is at time trip(tIs tIs
0.1Is/Im
0.9
t
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