Hitachi SJ700 Series Manual page 23

[ Main power supply]
Installation of an
AC reactor on the
input side
Using a private power
generator
Notes on Peripheral Equipment Selection
Wiring connections
Electromagnetic
contactor
Wiring
between
inverter and
Thermal relay
motor
Installing a circuit breaker
Wiring distance
Earth leakage relay
Phase advance capacitor
High-frequency Noise and Leakage Current
(1) High-frequency components are included in the input/output of the inverter main circuit, and they may cause interference in a transmitter, radio, or
sensor if used near the inverter. The interference can be minimized by attaching noise filters (option) in the inverter circuitry.
(2) The switching action of an inverter causes an increase in leakage current. Be sure to ground the inverter and the motor.
Lifetime of Primary Parts
Because a DC bus capacitor deteriorates as it undergoes internal chemical reaction, it should normally be replaced every 10 years. (10 years
is not the guaranteed lifespan but rather, the expected design lifespan.) Be aware, however, that its life expectancy is considerably shorter
when the inverter is subjected to such adverse factors as high temperatures or heavy loads exceeding the rated current of the inverter.
JEMA standard is the 5 years at ambient temperature 40ûC used in 12 hours daily. (according to the " Instructions for Periodic Inspection of
General-Purpose Inverter " (JEMA).)
Also, such moving parts as a cooling fan should be replaced. Maintenance inspection and parts replacement must be performed by only
specified trained personnel.
Precaution for Correct Usage
Before use, be sure to read through the Instruction Manual to insure proper use of the inverter.
Note that the inverter requires electrical wiring; a trained specialist should carry out the wiring.
The inverter in this catalog is designed for general industrial applications. For special applications in fields such as aircraft, outer space, nuclear
power, electrical power, transport vehicles, clinics, and underwater equipment, please consult with us in advance.
For application in a facility where human life is involved or serious losses may occur, make sure to provide safety devices to avoid a serious accident.
The inverter is intended for use with a three-phase AC motor. For use with a load other than this, please consult with us.
Information in this brochure is subject to change without notice.
In the following examples involving a general-purpose inverter, a large peak current flows on the main power supply side,
and is able to destroy the converter module. Where such situations are foreseen or the connected equipment must be
highly reliable, install an AC reactor between the power supply and the inverter. Also, where influence of indirect lightning
strike is possible, install a lightning conductor.
(A) The unbalance factor of the power supply is 3% or higher. (Note)
(B) The power supply capacity is at least 10 times greater than the inverter capacity (the power supply capacity is 500
kVA or more).
(C) Abrupt power supply changes are expected.
Examples:
(1) Several inverters are interconnected with a short bus.
(2) A thyristor converter and an inverter are interconnected with a short bus.
(3) An installed phase advance capacitor opens and closes.
In cases (A), (B) and (C), it is recommended to install an AC reactor on the main power supply side.
Note: Example calculation with V
V : R-S line voltage, V
RS ST
Unbalance factor of voltage = ---------------------------------------------------------------------------------------- X 100
V
= ----------------------------------------------- X 100 = ---------------------- X 100 = 1.5 (%)
An inverter run by a private power generator may overheat the generator or suffer from a deformed output voltage waveform
of the generator. Generally, the generator capacity should be five times that of the inverter (kVA) in a PWM control system,
or six times greater in a PAM control system.
(1) Be sure to connect main power wires with R(L1), S(L2), and T(L3) terminals (input) and motor wires to U(T1), V(T2),
and W(T3) terminals (output). (Incorrect connection will cause an immediate failure.)
(2) Be sure to provide a grounding connection with the ground terminal (
When an electromagnetic contactor is installed between the inverter and the motor, do not perform on-off switching during
running operation.
When used with standard applicable output motors (standard three-phase squirrel-cage four-pole motors), the SJ700 Series
does not need a thermal relay for motor protection due to the internal electronic protective circuit. A thermal relay, however,
should be used:
during continuous running outside a range of 30 to 60 Hz.
for motors exceeding the range of electronic thermal adjustment (rated current).
when several motors are driven by the same inverter; install a thermal relay for each motor.
The RC value of the thermal relay should be more than 1.1 times the rated current of the motor. Where the wiring length
is 10 m or more, the thermal relay tends to turn off readily. In this case, provide an AC reactor on the output side or use a
current sensor.
Install a circuit breaker on the main power input side to protect inverter wiring and ensure personal safety.
inverter-compatible circuit breaker. The conventional type may malfunction due to harmonics from the inverter. For more
information, consult the circuit breaker manufacturer.
The wiring distance between the inverter and the remote operator panel should be 20 meters or less. When this distance is
exceeded, use CVD-E (current-voltage converter) or RCD-E (remote control device). Shielded cable should be used on the
wiring. Beware of voltage drops on main circuit wires. (A large voltage drop reduces torque.)
If the earth leakage relay (or earth leakage breaker) is used, it should have a sensitivity level of 15 mA or more (per inverter).
Do not use a capacitor for power factor improvement between the inverter and the motor because the high-frequency
components of the inverter output may overheat or damage the capacitor.
= 205V, V = 201V, V = 200V
RS ST TR
: S-T line voltage, V : T-R line voltage
TR
Max. line voltage (min.) - Mean line voltage
Mean line voltage
- (V + V + V )/3
RS RS ST TR
(V + V + V )/3
RS ST TR
205 - 202
202
).
Choose an
50
40
30
2.5 5 10
Capacitor lifetime (years)
22