Mitsubishi Electric FR-A720-0.4K Instruction Manual page 516

Operation Panel
Indication
Name
Description
Check point
Corrective action
3 Speed detection hysteresis (Pr.870)
This function prevents chattering of the speed detection signals.
Parameter
Number
Speed detection
870
hysteresis
* Performing IPM parameter initialization changes the settings. (Refer to page 6)
Output
frequency
(Hz)
Pr.42
OFF
FB
ON
Example of the speed detection (FB) signal
REMARKS
 Setting a higher value to this parameter 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.
4 Limit regeneration avoidance operation frequency (Pr. 885)
The setting range of Pr.885 Regeneration avoidance compensation frequency limit value has been changed.
Parameter
Name
Number
Regeneration
avoidance
885
compensation
frequency limit value
E.OV3
Regenerative overvoltage trip during deceleration or stop
If regenerative energy causes the inverter's internal main circuit DC voltage to reach or exceed the
specified value, the protective circuit is activated to stop the inverter output. The circuit may also be
activated by a surge voltage produced in the power supply system.
· Check for sudden speed reduction.
 Check if the stall prevention operation is frequently activated in an application with a large
load inertia.
· Increase the deceleration time. (Set the deceleration time which matches the moment of inertia of the
load)
· Set the brake cycle longer.
· Use the regeneration avoidance function (Pr. 882 to Pr. 886). (
Manual (Applied).)
· Use the brake unit or power regeneration common converter (FR-CV) as required.
 Set Pr.154 Voltage reduction selection during stall prevention operation = "10 or 11". (
Chapter 4 of the Instruction Manual (Applied).)
Initial
Name
Value
0Hz*
OFF
ON
ON
Initial
Value
6Hz
FR-PU04
FR-PU07
Setting
Range
0 to 5Hz Set the hysteresis width for the detected frequency.

When an output frequency fluctuates, the following
signals may repeat ON/OFF (chatters).

Up to frequency (SU)
Pr.870

Speed detection (FB, FB2, FB3)

Low speed output (LS)
Setting hysteresis to the detected frequency prevents
chattering of these signals.
Setting
Range
Set the limit value of frequency which rises at
0 to 30Hz
activation of regeneration avoidance function.
9999 Frequency limit invalid
19/24
OV During Dec
Refer to Chapter 4 of the Instruction
Description
Description
BCN-C22005-634
Refer to