Speed Varies During Operation - Mitsubishi Electric FR-E700 Series Instruction Manual

Troubleshooting
7.6.8

Speed varies during operation

When Advanced magnetic flux vector control or the slip compensation is selected, the output fre-
quency varies between 0 and 2Hz as load fluctuates. This is a normal operation and not a fault.
Check Points
Input signal
Load
Input signal
Parameter
setting
Others
FR-E700SC EC
Possible Cause
Multi-speed command signal is chattering.
Load varies during an operation.
Frequency setting signal is varying.
The frequency setting signal is affected by
EMI.
Malfunction is occurring due to the undesira-
ble current generated when the transistor
output unit is connected.
Pr. 80 "Motor capacity" and Pr. 81 "Number of
motor poles" setting is improper for the
capacities of the inverter and the motor for
Advanced magnetic flux vector control or
General-purpose magnetic flux vector con-
trol.
Fluctuation of power supply voltage is too
large.
Hunting occurs by the generated vibration,
for example, when structural rigidity at load
side is insufficient.
Wiring length exceeds 30m when Advanced
magnetic flux vector control or General-pur-
pose magnetic flux vector control is per-
formed.
Wiring length is too long for V/F control, and
a voltage drop occurs.
Check first when you have troubles
Countermeasures
Take countermeasures to suppress chatter-
ing.
Select Advanced magnetic flux vector con-
trol or General-purpose magnetic flux vector
control.
Check the frequency reference signal.
Set filter to the analog input terminal using
Pr. 74 "Input filter time constant".
Take countermeasures against EMI, such as
using shielded wires for input signal lines.
Use terminal PC (terminal SD when source
logic) as a common terminal to prevent a
malfunction caused by undesirable current.
Check the Pr. 80 "Motor capacity" and Pr. 81
"Number of motor poles" setting.
Change the Pr. 19 "Base frequency voltage"
setting (about 3%) under V/F control.
Disable automatic control functions, such as
energy saving operation, fast-response cur-
rent limit function, regeneration avoidance
function, Advanced magnetic flux vector
control, General-purpose magnetic flux vec-
tor control, and stall prevention.
During the PID control, set smaller values to
Pr. 129 "PID proportional band" and Pr. 130
"PID integral time".
Lower the control gain, and adjust to
increase the stability.
Change Pr. 72 "PWM frequency selection"
setting.
Perform offline auto tuning.
Adjust Pr. 0 Torque boost by increasing with
0.5% increments for low-speed operation.
Change to Advanced magnetic flux vector
control or General-purpose magnetic flux
vector control.
Refer to
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