The voltage distortion on the mains supply voltage depends on the size of the harmonic currents multiplied by the mains impedance for the frequency
in question. The total voltage distortion THD is calculated on the basis of the individual voltage harmonics using this formula:
THD
% =
U
2
5 +
U
2
7 + ... +
U
2
N
(U
N
% of U)
2.9.5 Harmonics Emission Requirements
Equipment connected to the public supply network:
Options:
Definition:
1
IEC/EN 61000-3-2 Class A for 3-phase balanced equip-
ment (for professional equipment only up to 1 kW total
power).
2
IEC/EN 61000-3-12 Equipment 16A-75A and professio-
nal equipment as from 1 kW up to 16A phase current.
2.9.6 Harmonics Test Results (Emission)
Power sizes up to PK75 in T2 and T4 complies with IEC/EN 61000-3-2 Class A. Power sizes from P1K1 and up to P18K in T2 and up to P90K in T4 complies
with IEC/EN 61000-3-12, Table 4. Power sizes P110 - P450 in T4 also complies with IEC/EN 61000-3-12 even though not required because currents are
above 75 A.
Individual Harmonic Current I
n
/I
1
(%)
Harmonic current distortion factor (%)
I
5
I
7
I
11
I
13
THD
PWHD
Actual (typical)
40
20
10
8
46
45
Limit for R
sce
≥120
40
25
15
10
48
46
Table 2.2: Harmonics test results (Emission)
Provided that the short-circuit power of the supply S
sc
is greater than or equal to:
SSC
= 3 ×
RSCE
×
Umains
×
Iequ
= 3 × 120 × 400 ×
Iequ
at the interface point between the user’s supply and the public system (R
sce
).
It is the responsibility of the installer or user of the equipment to ensure, by consultation with the distribution network operator if necessary, that the
equipment is connected only to a supply with a short-circuit power S
sc
greater than or equal to specified above.
Other power sizes can be connected to the public supply network by consultation with the distribution network operator.
Compliance with various system level guidelines:
The harmonic current data in the table are given in accordance with IEC/EN61000-3-12 with reference to the Power Drive Systems product standard.
They may be used as the basis for calculation of the harmonic currents' influence on the power supply system and for the documentation of compliance
with relevant regional guidelines: IEEE 519 -1992; G5/4.
2.9.7 Immunity Requirements
The immunity requirements for frequency converters depend on the environment where they are installed. The requirements for the industrial environment
are higher than the requirements for the home and office environment. All Danfoss frequency converters comply with the requirements for the industrial
environment and consequently comply also with the lower requirements for home and office environment with a large safety margin.
In order to document immunity against electrical interference from electrical phenomena, the following immunity tests have been made on a system
consisting of a frequency converter (with options if relevant), a screened control cable and a control box with potentiometer, motor cable and motor.
The tests were performed in accordance with the following basic standards:
2 Introduction to VLT HVAC Drive
VLT
®
HVAC Drive Design Guide
42
MG.11.B9.02 - VLT
®
is a registered Danfoss trademark
2