Mitsubishi Electric FR-F820-04750 Instruction Manual page 399

Parameters
Speed detection hysteresis (Pr. 870)
● This function prevents chattering of the speed detection signals. When an output frequency
fluctuates, the up to frequency signal (SU) and the speed detection signals (FB and FB2) may
repeat ON/OFF (chatter).
Setting hysteresis to the detected frequency prevents chattering of these signals.
Output
frequency
(Hz)
Pr. 42
OFF
FB
SU output level
Set frequency
SU output level
Fig. 5-100:
NOTES 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, 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
PM motor control
Setting a higher value in Pr. 870 slows the response of frequency detection signals (SU, FB, FB2).
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
FR-F800
ON
ON
ON
Output
frequency
(Hz)
Pr. 870
Pr. 870
Pr. 41
Pr. 870
Pr. 870
SU signal
Example of the up to frequency (SU) signal
FU, FU2
Output frequency
Output frequency before the slip
compensation
Frequency command value
(output terminal function selection)
(M) Monitor display and monitor output signal
Fig. 5-99:
Example of the speed detection (FB) signal
Pr. 870
OFF
ON ON
Compared frequency
ON
FB, FB2, SU
Output frequency
Output frequency before the slip
compensation
Estimated frequency (actual motor
speed)
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Time
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