
2 Engineering
2.2 Electrical power network
DB1 variable frequency drive
11/20 MN040031EN
Eaton.com
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2.2.4 Total harmonic distortion (THD)
The THD value (THD = total harmonic distortion) is defined in standard
IEC/EN 61800-3 as the ratio of the rms value of all harmonic components to
the rms value of the fundamental frequency.
2.2.5 Reactive power compensation devices
Compensation on the mains side is not required for the variable frequency
drives of the DB1 series. From the AC power supply network, they only take
on very little reactive power of the fundamental harmonics (cos
ϕ
~ 0.98).
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In order to reduce the THD value (up to 30 %), it is recommen-
ded to use a DX-LN… mains choke
(
section 2.5, “Mains chokes”, page 41).
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Power factor compensation (PFC)
Thanks to power factor compensation (PFC), the DB1 variable
frequency drive achieves superior harmonic correction.
This eliminates the need for additional accessories for harmonic
compensation and saves space and installation time.
With the PFC devices, the requirements of the DIN EN 61000-3-2
standard for household applications can be easily met.
The DB1 variable frequency drives with PFC are available with a
single-phase 230-V voltage input in the power ratings 0.75 kW
and 1.5 kW.
The DB1 variable frequency drive for a motor output of 0.75 kW
has a multi-voltage input (110 V - 230 V).
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In the AC supply systems with non-choked reactive current
compensation devices, current oscillations, (harmonics), parallel
resonances and undefined conditions can occur.
In the project planning for the connection of variable frequency
drives to AC supply systems with undefined circumstances,
consider using mains chokes.