Toshiba VF-nC1 - Manual (Page 18)

E6581090
A-9
1
1.4 Notes on the application
1.4.1 Motors
When the VF-nC1 and the motor are used in conjunction, pay attention to the following items.
Warning
Mandatory
Use an inverter that conforms to the specifications of the three-phase induction motor
and power supply being used. If the inverter being used does not conform to those
specifications, not only will the three-phase induction motor not rotate correctly, but it
may causes serious accidents through overheating and fire.
Comparisons with commercial power operation.
The VF-nC1 Inverter employs the sinusoidal PWM system. However, the output voltage and
output current do not assume a precise sine wave, they have a distorted wave that is close to
sinusoidal waveform. This is why compared to operation with a commercial power there will be
a slight increase in motor temperature, noise and vibration.
Operation in the low-speed area
When running continuously at low speed in conjunction with a general purpose motor, there
may be a decline in that motor's cooling effect. If this happens, operate with the output
decreased from rated load.
If you want to run continuously low speed operations at rated torque, please use the VF motor
made especially for Toshiba inverter. When operating in conjunction with a VF motor, you must
change the inverter's motor overload protection level to "VF motor use (QNO)".
Adjusting the overload protection level
The VF-nC1 Inverter protects against overloads with its overload detection circuits (electronic
thermal). The electronic thermal's reference current is set to the inverter's rated current, so that
it must be adjusted in line with the rated current of the general purpose motor being used in
combination.
High speed operation at and above 60Hz
Operating at frequencies greater than 60Hz will increase noise and vibration. There is also a
possibility that such operation will exceed the motor's mechanical strength limits and the
bearing limits so that you should inquire to the motor's manufacturer about such operation.
Method of lubricating load mechanisms.
Operating an oil-lubricated reduction gear and gear motor in the low-speed areas will worsen
the lubricating effect. Check with the manufacturer of the reduction gear to find out about
operable gearing area.
Extremely low loads and low inertia loads
The motor may demonstrate instability such as abnormal vibrations or overcurrent trips at light
loads of 50 percent or under of the load percentage, or when the load's inertia moment is
extremely small. If that happens reduce the carrier frequency.
Occurrence of instability
Unstable phenomena may occur under the load and motor combinations shown below.
• Combined with a motor that exceeds applicable motor ratings recommended for the inverter
• Combined with special motors such as explosion-proof motors
To deal with the above lower the settings of inverter carrier frequency.
• Combined with couplings between load devices and motors with high backlash
• Combined with loads that have sharp fluctuations in rotation such as piston movements
Braking a motor when cutting off power supply
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.