Toshiba VF-FS1 Inverters, Braking motor, Measures to protect motors against surge voltages

E6581381

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	1
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.

1.4.2Inverters

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.

A-15