3.2 Power supply harmonics 1 3.2.1 Power supply harmonics 2 correction capacitor etc. Power supply harmonics are different from noise and leakage currents in source, frequency band and The inverter may generate power supply harmonics from its converter circuit to affect the power generator, power factor transmission path. Take the following countermeasure suppression techniques. 3 • Differences between harmonics and noises 5 5 6 • Countermeasures The harmonic current generated from the inverter to the input side differs according to various conditions such as the wiring 7 impedance, whether a reactor is used or not, and output frequency and output current on the load side.
For the output frequency and output current, we understand that this should be calculated in the conditions under the rated load at the maximum operating frequency. 8 MCCB MC Power supply R S Y X U R/L1 9 T Z S/L2 T/L3 W V M AC reactor (FR-HAL) Do not install power factor improving capacitor. Inverter 10 • The power factor improving capacitor and surge suppressor on the inverter output side may be overheated or damaged by the harmonic components of the inverter output. Also, since an excessive current flows in the inverter to activate overcurrent protection, do not provide a capacitor and surge suppressor on the inverter output side when the motor is driven by the inverter.
For power factor improvement, install a reactor on the inverter input side. 3.2.2 Harmonic suppression guidelines in Japan Inverters have a converter section (rectifier circuit) and generate a harmonic current. Harmonic currents flow from the inverter to a power receiving point via a power transformer. The Harmonic Suppression Guidelines was established to protect other consumers from these outgoing harmonic currents.
The three-phase 200 V input specifications 3.7 kW or lower were previously covered by "the Harmonic Suppression Guidelines for Household Appliances and General-purpose Products" and other models were covered by "the Harmonic Suppression Guidelines for Consumers Who Receive High Voltage or Special High Voltage". However, the transistorized inverter has been excluded from the target products covered by "the Harmonic Suppression Guidelines for Household Appliances and General- purpose Products" in January 2004 and "the Harmonic Suppression Guideline for Household Appliances and General-purpose Products" was repealed on September 6, 2004.
All capacity and all models of general-purpose inverter used by specific consumers are now covered by "the Harmonic Suppression Guidelines for Consumers Who Receive High Voltage or Special High Voltage" (hereinafter referred to as "the Specific Consumer Guidelines"). 53 3. PRECAUTIONS FOR USE OF THE INVERTER 3.2 Power supply harmonics Item Harmonics Noise frequency Normally 40th to 50th degrees or less (3 kHz or less). High frequency (several 10 kHz to 1 GHz order). Location To-electric channel, power impedance. To-space, distance, wiring path. Quantitative understanding Theoretical calculation possible. Random occurrence, quantitative grasping difficult.
Generated amount Nearly proportional to the load capacity. Changes with the current variation ratio. (Gets larger as switching speed increases.) Affected equipment immunity Specified by standards per equipment. Different depending on maker's equipment specifications. Countermeasure Provide a reactor. Increase distance. NOTE