Toshiba VF-nC1 - Manual (Page 19)

E6581090
A-10
1
Loads that generate negative torque
When combined with loads that generate negative torque the protection for overvoltage and
overcurrent on the inverter will go into operation and may cause a trip. For this kind of situation,
you must install a dynamic braking resistor, etc. that complies with the load conditions.
Motor with brake
If a motor with brake is connected directly to the output side of the inverter, the brake will not
release because voltage at startup is low. Wire the brake circuit separately from the motor's
main circuits.
Circuit configuration 1 Circuit configuration 2
MC1
MC2
B
P15
FM/
OUT Three-phase
power supply
MC3
MC2
MC1
MC2
B
IM
MC3
MC1
MC3
FLB FLC ST CC Three-phase
power supply
MC2
IM
RY
＋ ―
RY
In circuit configuration 1, the brake is turned on and off through MC2 and MC3. If the circuit is
configured in some other way, the overcurrent trip may be activated because of the locked rotor
current when the brake goes into operation. Circuit configuration 2 uses low-speed signal
FM/OUT to turn on and off the brake. Turning the brake on and off with a low-speed signal may
be better in such applications as elevators. Please confer with us before designing the system.
1.4.2 Inverters
Protecting inverters from overcurrent
The inverter has an overcurrent protection function. However because the programmed current
level is set to the inverter's maximum applicable motor, if the motor is one of small capacity and
it is in operation, the overcurrent level and the electronic thermal protection must be readjusted.
If adjustment is necessary, see 5-10 in Chapter 5, and make adjustments as directed.
Inverter capacity
Do not operate a large capacity motor with a small capacity (kVA) inverter even with light loads.
Current ripple will raise the output peak current making it easier to set off the overcurrent trip.
Power factor improving capacitors
Power factor improving capacitors cannot be installed on the output side of the inverter. When a
motor is run that has a power factor improving capacitor attached to it, remove the capacitors.
This can cause inverter malfunction trips and capacitor destruction.
Remove the power factor improving
capacitor and surge absorber
Power factor improving capacitor
U
V
W
Inverter IM
Operating at other than rated voltage
Connections to voltages other than the rated voltage described in the rating label cannot be
made. If a connection must be made to a power supply other than one with rated voltage, use a
transformer to raise or lower the voltage to the rated voltage.