Avoiding Motor Overrunning; Speed Deviation Excess Detection; Speed Limit - Mitsubishi FR-A800 Instruction Manual

Speed control under Real sensorless vector control, vector control, PM sensorless vector
control
5.3.9

Avoiding motor overrunning

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
285
excess detection
H416
frequency

853

Speed deviation time
H417
873


Speed limit

H415
690 Deceleration check
H881 time

This is the overspeed detection frequency under encoder feedback control. (Refer to

These parameters are available when FR-A8AP (option) is installed.
Speed deviation excess detection (Pr.285, Pr.853)
• A trip can be set for when the deviation between the set frequency and actual rotation speed is large, such as when the
load torque is excessive.
• When the difference (absolute value) between the speed command value and actual rotation speed in speed control under
vector control is equal to 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, Speed deviation excess
detection (E.OSD) activates to shut off the inverter output.
Speed limit (Pr.873)
• This function prevents overrunning even when the setting value for the number of encoder pulses 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).
Actual speed
at error occurrence
206
PARAMETERS
Initial
Setting range
value
0 to 30 Hz
9999
9999
1 s 0 to 100 s
20 Hz 0 to 400 Hz
0 to 3600 s
1 s
9999
Pr.853
Fault output
OFF
(ALM)
Speed deviation
excessive fault activated
Set speed + Pr. 873 value
Vector Vector Vector
Description
Set the speed deviation excess detection frequency (difference
between the actual rotation speed and speed command value)
at which the protective function (E.OSD) activates.
No speed deviation excess
Set the time from when the speed deviation excess state is
entered to when the protective function (E.OSD) activates.
Set the frequency limit with the set frequency + Pr.873 value.
Set the time required to shut off output due to deceleration
check after the start signal is OFF.
No deceleration check
page 626.)
Set frequency
Pr.285
Actual speed
Time
ON
(E. OSD)
Value of Pr. 873
Set speed
Speed during
normal operation