Справочник Пользователя для Mitsubishi Electronics FR-A700

Prevent the motor from overrunning (Pr. 285, Pr. 853, Pr. 873) 

When the deviation between the set frequency and actual speed is large, e.g. too large load torque, this function can
cause the inverter to provide a speed deviation excessive fault (E.OSD) and come to a trip.

This function prevents the motor from overrunning when the setting of number of encoder pulses and the actual
number differ.
When the setting of number of encoder pulses is smaller than the actual number, the motor may increase its speed.
To prevent this, restrict the output frequency with frequency (obtained by adding the set frequency and Pr. 873 ).

This function prevents the motor from overrunning when the load torque is too large and incorrect number of the
encoder is set.

9999

9999

Without speed deviation excessive

0 to 30Hz

If the difference (absolute value) between the 
speed command value and actual speed during 
speed control under vector control exceeds the 
Pr. 285 Excessive speed deviation detection 
frequency for more than the time set in Pr. 853 
Speed deviation time, speed deviation excessive 
occurs and inverter fault (E. OSD) appears, 
resulting in a trip.

1.0s

0 to 100s

20Hz

0 to 120Hz

Frequency is limited at the set frequency + Pr. 873.

*1

Acts as Overspeed detection frequency under encoder feed back operation. (Refer to page 217)

*2

This parameter can be set when the FR-A7AP/FR-A7AL (option) is mounted.

⋅ If automatic restart after instantaneous power failure (Pr. 57 ≠ 9999) is selected when the setting of number of encoder pulses is

smaller than the actual number, the output speed is limited with the synchronous speed obtained by adding the maximum
setting (Pr. 1) and Pr. 873 setting.

⋅ When speed limit function is activated due to regenerative torque limit, output torque may suddenly decrease. In addition,

output phase loss (E.LF) may occur when speed limit function is activated during pre-excitation.
When the setting of number of encoder pulses are correct, it is recommended to set a maximum value (120Hz) in Pr. 873.

⋅ Even when the set frequency is lowered after the inverter has been started, the speed limit value does not decrease. Note that

the speed is limited to speed command + Pr. 873 setting during deceleration.

Set frequency

Actual speed

Time

Speed deviation

excessive fault activated

(E. OSD)

ON

OFF

Fault output
(across A-C)

Frequency

(Hz)

Actual speed 
at error occurrence

Set speed + Pr. 873 value

Value of Pr. 873 

Set speed

Speed during 
normal operation.