Mitsubishi Electric FR-A820-00046 Instruction Manual page 594

(M) Monitor display and monitor output signal
Low speed detection (LS signal, Pr. 865)
● When the output frequency (refer to the table below) drops to the Pr. 865 "Low speed detection"
setting or lower, the low speed detection signal (LS) is output.
● In speed control under Real sensorless vector control, vector control or PM sensorless vector
control, when the frequency drops to the Pr. 865 setting, the output torque exceeds the Pr. 874
"OLT level setting" setting, and this status continues for 3 s, a fault (E.OLT) appears and the inverter
output stops.
● For the LS signal, set "34 (positive logic) or 134 (negative logic)" in any of Pr. 190 to Pr. 196 (output
terminal function selection) to assign the function to the output terminal.
LS
Speed detection hysteresis (Pr. 870)
● This function prevents chattering of the speed detection signals. When an output frequency
fluctuates, the following signals may repeat ON/OFF (chatter):
– Up to frequency signal (SU)
– Speed detection signal (FB, FB2, FB3)
– Low speed output signal (LS)
Setting hysteresis to the detected frequency prevents chattering of these signals.
Output
frequency
(Hz)
Pr. 42
OFF
FB
Example of the speed detection (FB) signal
Output frequency
(Hz)
SU output
level
Set
frequency
SU output
level
SU signal
5 - 392
Pr. 865
OFF
ON
ON
ON
Pr. 870
Pr. 870
Pr. 870
Pr. 870
Pr. 41
Pr. 41
Pr. 870
Pr. 870
Pr. 870
Pr. 870
ON ON
Fig. 5-176:
Low speed detection
Time
ON
Fig. 5-177:
Output of the speed detection (FB) signal
Pr. 870
OFF
ON
Fig. 5-178:
Output of the up to frequency (SU) signal
Time
ON
Parameters
I002628E
I002629E
I002858E