5–3

SJ300 Inverter

Component Descriptions

AC Reactors, Input SideAC Reactor or LCR Filter, Output Side

This is useful in suppressing harmonics induced on the power supply lines, or when the main power voltage imbalance exceeds 3% (and power source capacity is more than 500 kVA), or to smooth out line fluctuations. It also improves the power factor.

In the following cases for a general-purpose inverter, a large peak current flows on the main power supply side, and is able to destroy the inverter module:

•If the unbalanced factor of the power supply is 3% or higher

•If the power supply capacity is at least 10 times greater than the inverter capacity (the power supply capacity is 500 kVA or more)

•If abrupt power supply changes are expected

Examples of these situations include:

1.Several inverters are connected in parallel, sharing the same power bus

2.A thyristor converter and an inverter are connected in parallel, sharing the same power bus

3.An installed phase-advance (power factor correction) capacitor opens and closes

Where these conditions exist or when the connected equipment must be highly reliable, install an AC reactor between the power supply and the inverter. Also, where the effects of an indirect lightning strike is possible, install a lightning conductor.

Example calculation:

VRS = 205V, VST = 203V, VTR = 197V,

where VRS is R-S line voltage, VST is S-T line voltage, VTR is T-R line voltage

Unbalance factor of voltage = Max.-----------------------------------------------------------------------------------------------------------line voltage (min.) – Mean line voltage ⋅ 100

 

 

Meanline voltage

 

=

VRS – (VRS + VST + VTR) ⁄ 3

⋅ 100 =

205 – 202

⋅ 100 = 1.5%

-------------------------------------------------------------------------(VRS+ VST + VTR) ⁄ 3

-----------------------202

 

 

 

Please refer to the documentation that comes with the AC reactor for installation instructions.

This reactor reduces the vibrations in the motor caused by the inverter’s switching waveforms, by smoothing the waveforms to approximate commercial power quality. It is also useful to reduce the reflected voltage wave phenomenon when wiring from the inverter to the motor is more than 10m in length. Please refer to the documentation that comes with the AC reactor for installation instructions.

Accessories

Control Motor