Mitsubishi Electric 800 Series Instruction Manual page 382

Low speed detection (LS signal, Pr.865)
Pr.865
LS ON OFF
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
FB
ON
Example of the speed detection (FB) signal
NOTE
• In the initial setting, the FU signal is assigned to the terminal FU, and the SU signal is assigned to the terminal SU.
• All signals turn OFF during DC injection brake, pre-excitation (zero speed control, servo lock) and tuning at start-up.
• Each signal's reference frequency differs by the control method.
Control method
V/F control
Advanced magnetic flux vector control
Real sensorless vector control
Encoder feedback control
vector control
PM sensorless vector control
• Setting a higher value in Pr.870 slows the response of frequency detection signals (SU, FB, FB2, FB3, and LS).
• The ON/OFF logic for the LS signal is opposite for the FB signal.
• Changing the terminal assignment using Pr.190 to Pr.196 (Output terminal function selection) may affect the other
functions. Set parameters after confirming the function of each terminal.
Parameters referred to ???????
Pr.190 to Pr.196 (Output terminal function selection)
Pr.874 OLT level setting page 154
Time
ON
Output frequency
Pr.870
ON
ON
FU, FU2, FU3
Output frequency
Output frequency before the slip
compensation
Frequency command value
Actual motor speed converted as frequency
Frequency command value
Frequency command value
page 370
(M) Monitor display and monitor output signal
• 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.
(Hz)
Pr.870
SU output level
Pr.870
Pr.41
Set frequency
Pr.870
SU output level
Pr.870
SU signal
Example of the up to frequency (SU) signal
Compared frequency
Output frequency
Output frequency before the slip
compensation
Estimated frequency (estimated from the
actual motor speed)
Actual motor speed converted as frequency
Actual motor speed converted as frequency
Estimated frequency (actual motor speed)
ON ON
ON
FB, FB2, FB3, SU, LS
PARAMETERS
Time
5
GROUP
M
381