Notes On Peripheral Equipment Selection; High-Frequency Noise And Leakage Current; Lifetime Of Primary Parts - Hitachi SJ300 Series Manual

[ 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 five years. 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.
The approximate lifetime of the capacitor is as shown in the figure at the right when it is used 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.
45
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 high-
ly 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 = 205V, V
RS
V : R-S line voltage, V : S-T line voltage, V
RS ST
Max. line voltage (min.) - Mean line voltage
Unbalance factor of voltage = ---------------------------------------------------------------------------------------- × 100
V
RS
= ----------------------------------------------- × 100 = ---------------------- × 100 = 1.5 (%)
(V
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 SJ300 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. Choose an
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.
= 201V, V = 200V
ST TR
: T-R line voltage
TR
Mean line voltage
- (V + V + V )/3
205 - 202
RS ST TR
+ V + V )/3
RS ST TR
202
).
50
40
30
2.5
Capacitor lifetime (years)
5 10