Avoiding Motor Overrunning - Mitsubishi Electric 800 Series Instruction Manual (Function

5.8

Avoiding motor overrunning

Vector Vector Vector PM PM PM
Motor overrunning due to excessive load torque or an error in the setting of the number of encoder pulses can be avoided.
Pr. Name
Speed deviation excess detection
285
*1
H416
frequency
853
Speed deviation time
H417
*2
873
Speed limit
H415
690
Deceleration check time
H881
*1 This is the overspeed detection frequency under encoder feedback control. (Refer to
*2 The setting is available when a Vector control compatible option is installed.
 Speed deviation excess detection (Pr.285, Pr.853)
• A shutoff can be set for when the deviation between the set frequency and the rotation speed (estimated value under PM
sensorless vector control) is large, such as when the load torque is excessive.
• When the difference (absolute value) between the speed command value and the rotation speed (estimated value under
PM sensorless vector control) is equal to or higher than the setting value in Pr.285 Speed deviation excess detection
frequency for a continuous time equal to or longer than the setting value in Pr.853 Speed deviation time, the speed
deviation excess detection (E.OSD) is activated to shut off the inverter output.
Pr.853
Fault output
OFF
(ALM)
Speed deviation
excessive fault activated
NOTE
• This function is enabled at a frequency equal to or higher than 10% of the rated motor frequency under PM sensorless vector
control.
 Speed limit (Pr.873)
• This function prevents overrunning even when the setting value for and the value of the actual number of pulses are
different. When the setting value for the number of encoder pulses is lower than the actual number of pulses, because the
motor may increase speed, the output frequency is limited with the frequency of (set frequency + Pr.873).
Set speed + Pr. 873 value
Actual speed
at error occurrence
Initial value
9999
1.0 s
20 Hz
1.0 s
Set frequency
Pr.285
Rotation speed (estimated value
when PM sensorless vector control is used)
Time
ON
(E. OSD)
Setting
range
Set the speed deviation excess detection frequency
(difference between the rotation speed (estimated value)
0 to 30 Hz
and the speed command value) at which the protective
function (E.OSD) activates.
9999 No speed deviation excess
Set the time from when the speed deviation excess state
0 to 100 s is entered to when the protective function (E.OSD)
activates.
Set the frequency limit with the set frequency + Pr.873
0 to 400 Hz
value.
Set the time required to shut off output due to
0 to 3600 s
deceleration check.
9999 No deceleration check
page 495).
Value of Pr. 873
Set speed
Speed during
normal operation
Description
5. Speed Control
5.8 Avoiding motor overrunning
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