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EMC and leakage currents
1) Calculation of equivalent capacity (P0) of harmonic generating equipment
The "equivalent capacity" is the capacity of a 6-pulse converter converted from the capacity of consumer's harmonic
generating equipment and is calculated with the following equation. If the sum of equivalent capacities is higher than the
limit in Table 3, harmonics must be calculated with the following procedure:
2) Calculation of outgoing harmonic current
Outgoing harmonic current = fundamental wave current (value converted from received power voltage) × operation ratio ×
harmonic content
Operation ratio: Operation ratio = actual load factor × operation time ratio during 30 minutes
Harmonic content: Found in Table 4.
3) Application of the guideline for specific consumers
If the outgoing harmonic current is higher than the maximum value per 1kW contract power × contract power, a harmonic
suppression technique is required.
4) Harmonic suppression techniques
P0 =
Σ(Ki×Pi) [kVA]
∗ Rated capacity: Determined by the capacity of the applied motor and
found in Table 5. It should be noted that the rated capacity used here is
used to calculate generated harmonic amount and is different from the
power supply capacity required for actual inverter drive.
Ki: Conversion factor (refer to Table 2)
Pi: Rated capacity of harmonic generating equipment∗[kVA]
i: Number indicating the conversion circuit type
Table 5 Rated Capacities and Outgoing Harmonic Currents for Inverter Drive
Applicable
Motor (kW)
Rated Current [A]
Fundamental
Wave Current
Converted
from 6.6kV
(mA)
Rated
Capacity
(kVA)
Outgoing Harmonic Current Converted from 6.6kV(mA)
(No reactor, 100% operation ratio)
200V 400V 5th 7th 11th 13th 17th 19th 23rd 25th
0.4
1.61 0.81 49 0.57 31.85 20.09 4.165 3.773 2.107 1.519 1.274 0.882
0.75 2.74 1.37 83 0.97 53.95 34.03 7.055 6.391 3.569 2.573 2.158 1.494
1.5 5.50 2.75 167 1.95 108.6 68.47 14.20 12.86 7.181 5.177 4.342 3.006
2.2 7.93 3.96 240 2.81 156.0 98.40 20.40 18.48 10.32 7.440 6.240 4.320
3.7 13.0 6.50 394 4.61 257.1 161.5 33.49 30.34 16.94 12.21 10.24 7.092
5.5 19.1 9.55 579 6.77 376.1 237.4 49.22 44.58 24.90 17.95 15.05 10.42
7.5 25.6 12.8 776 9.07 504.4 318.2 65.96 59.75 33.37 24.06 20.18 13.97
11 36.9 18.5 1121 13.1 728.7 459.6 95.29 86.32 48.20 34.75 29.15 20.18
15 49.8 24.9 1509 17.6 980.9 618.7 128.3 116.2 64.89 46.78 39.24 27.16
No. Item Description
1
Reactor installation
(FR-HAL, FR-HEL)
Install an AC reactor (FR-HAL) on the AC side of the inverter or a DC reactor (FR-HEL) on its DC side
or both to suppress outgoing harmonic currents.
2
Installation of power factor
improving capacitor
When used with a series reactor, the power factor improving capacitor has an effect of absorbing
harmonic currents.
3
Transformer multi-phase
operation
Use two transformers with a phase angle difference of 30° as in -Δ, Δ-Δ combination to provide an
effect corresponding to 12 pulses, reducing low-degree harmonic currents.
4
Passive filter
(AC filter)
A capacitor and a reactor are used together to reduce impedances at specific frequencies, producing a
great effect of absorbing harmonic currents.
5
Active filter
(Active filter)
This filter detects the current of a circuit generating a harmonic current and generates a harmonic
current equivalent to a difference between that current and a fundamental wave current to suppress a
harmonic current at a detection point, providing a great effect of absorbing harmonic currents.