Toshiba TOSVERT VF-FS1 Instruction Manual page 26

Low loads and low inertia loads
Occurrence of instability
1
Braking a motor when cutting off power supply
Load that produces regenerative torque
The motor may demonstrate instability such as abnormal vibrations or overcurrent trips at light loads of
50 % or under of the load percentage, or when the load's inertia moment is extremely small. If that
happens reduce the carrier frequency.
Unstable phenomena may occur with the load and motor combinations shown below.
⋅ Combined with a motor that exceeds applicable motor ratings recommended for the inverter
⋅ Combined with special motors
To deal with the above lower the settings of inverter carrier frequency.
⋅ Combined with couplings between load devices and motors with high backlash
When using the inverter in the above combination, use the S-pattern acceleration/deceleration function,
or when vector control is selected, adjust the speed control response/stability factor or switch to V/F
control mode.
⋅ Combined with loads that have sharp fluctuations in rotation such as piston movements
In this case, please do not use this inverter.
A motor with its power cut off goes into free-run, and does not stop immediately. To stop the motor
quickly as soon as the power is cut off install an auxiliary brake. There are different kinds of brake
devices, both electrical and mechanical. Select the brake that is best for the system.
Do not use the inverter in combination with a load, such as an air conditioner, that produces
regenerative torque. Or the overvoltage or overcurrent protection circuit of the inverter may be activated,
causing the inverter to trip. If overvoltage tripping occurs during deceleration, lengthen the deceleration
time.
A-14
E6581381