Toshiba TOSVERT VF-FS1 Series, Instruction Manual

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E6581381
A-15
1
Braking motor
When using a braking motor, if the braking circuit is directly connected to the inverters's output
terminals, the brake cannot be released because of the lowered starting voltage. Therefore, when
using a braking motor, connect the braking circuit to the inverter's power supply side, as shown in the
figure below. Usually, braking motors produce larger noise in low speed ranges.
Note: In the case of the circuit shown on the below, assign the function of detecting low-speed signals
to the RY and RC terminals. Make sure the parameter
H
is set to (factory default
setting).
Measures to protect motors against surge voltages
In a system in which a 400V-class inverter is used to control the operation of a motor, very high surge
voltages may be produced. When applied to the motor coils repeatedly for a long time, may cause
deterioration of their insulation, depending on the cable length, cable routing and types of cables used.
Here are some examples of measures against surge voltages.
(1)
Lower the inverter’s carrier frequency.
(2) Set the parameter
H
(Carrier frequency control mode selection) to or .
(3) Use a motor with high insulation strength.
(4) Insert an AC reactor or a surge voltage suppression filter between the inverter and the motor.
1.4.2 Inverters
Protecting inverters from overcurrent
The inverter has an overcurrent protection function. The programmed current level is set to the
inverter's maximum applicable motor. If the motor used has a small capacity, the overcurrent level and
the electronic thermal protection must be readjusted. If adjustment is necessary, see 5.12, and make
adjustments as directed.
Inverter capacity
Do not use a small-capacity (kVA) inverter to control the operation of a large-capacity motor (two-class
or more larger motor), no matter how light the load is. Current ripple will raise the output peak current
making it easier to set off the overcurrent trip.