12
PRECAUTIONS FOR USE OF
THE INVERTER
(13) Provide electrical and mechanical interlocks for MC1
and MC2 which are used for bypass operation.
When the wiring is incorrect or if there is an electronic
bypass circuit as shown on the right, the inverter will be
damaged by leakage current from the power supply
due to arcs generated at the time of switch-over or
chattering caused by a sequence error.
(14) If the machine must not be restarted when power is restored after a power failure, provide a magnetic contactor in
the inverter's input side and also make up a sequence which will not switch on the start signal.
If the start signal (start switch) remains on after a power failure, the inverter will automatically restart as soon as
the power is restored.
(15) Instructions for overload operation
When performing an operation of frequent start/stop with the inverter, rise/fall in the temperature of the transistor
element of the inverter will repeat due to a continuous flow of large current, shortening the life from thermal fatigue.
Since thermal fatigue is related to the amount of current, the life can be increased by reducing current at locked
condition, starting current, etc. Decreasing current may increase the life. However, decreasing current will result in
insufficient torque and the inverter may not start. Therefore, choose the inverter which has enough allowance for
current (up to 2 rank larger in capacity).
(16) Make sure that the specifications and rating match the system requirements.
(17) A motor with encoder is necessary for vector control. In addition, connect the encoder directly to the backlash-free
motor shaft. An encoder is not necessary for real sensorless vector control.
MC2
MC1
U
V
W
R/L1
S/L2
T/L3
IM
Power supply
Inverter
Undesirable current
Interlock
A760_installation_guideline_NA.book 12 ページ ２００７年１月１０日 水曜日 午前８時４９分
Summary of Contents for FR-A760-00017-NA
Page 27: ...25 MEMO ...
