Harmonic Mitigation; Harmonic Calculation; Galvanic Isolation (Pelv); Pelv - Protective Extra Low Voltage - Danfoss VLT AutomationDrive FC 300 Design Manual

Introduction

3.6.3 Harmonic Mitigation

In cases where additional harmonic suppression is required
Danfoss offers a wide range of mitigation equipment.
These are:
•
12-pulse drives
•
AHF filters
•
Low Harmonic Drives
•
Active Filters
The choice of the right solution depends on several
factors:
•
The grid (background distortion, mains
unbalance, resonance and type of supply
(transformer/generator)
•
Application (load profile, number of loads and
load size)
•
Local/national requirements/regulations (IEEE519,
IEC, G5/4, etc.)
•
Total cost of ownership (initial cost, efficiency,
maintenance, etc.)
Always consider harmonic mitigation if the transformer
load has a non-linear contribution of 40% or more.

3.6.4 Harmonic Calculation

Determining the degree of voltage pollution on the grid
and needed precaution is done with the Danfoss MCT31
calculation software. Download the free tool VLT
Harmonic Calculation MCT 31 from www.danfoss.com. The
software is built with a focus on user-friendliness and
limited to involve only system parameters that are
normally accessible.

3.7 Galvanic Isolation (PELV)

3.7.1 PELV - Protective Extra Low Voltage

PELV offers protection by way of extra low voltage.
Protection against electric shock is ensured when the
electrical supply is of the PELV type and the installation is
made as described in local/national regulations on PELV
supplies.
All control terminals and relay terminals 01-03/04-06
comply with PELV (Protective Extra Low Voltage), with the
exception of grounded Delta leg above 400 V.
Galvanic (ensured) isolation is obtained by fulfilling
requirements for higher isolation and by providing the
RSPSupply - 1-888-532-2706 - www.RSPSupply.com
http://www.RSPSupply.com/p-21462-Danfoss-131B8966-VLT-Automation-VT-Drive-VFD-FC301-230V-5-HP.aspx
®
VLT AutomationDrive FC 300 Design Guide, 0.25-75 kW
relevant creepage/clearance distances. These requirements
are described in the EN 61800-5-1 standard.
The components that make up the electrical isolation, as
described below, also comply with the requirements for
higher isolation and the relevant test as described in EN
61800-5-1.
The PELV galvanic isolation can be shown in six locations
(see Illustration 3.27):
In order to maintain PELV all connections made to the
control terminals must be PELV, e.g. thermistor must be
reinforced/double insulated.
®
Illustration 3.27 Galvanic Isolation
The functional galvanic isolation (a and b on drawing) is
for the 24 V back-up option and for the RS-485 standard
bus interface.
Installation at high altitude:
380-500 V, enclosure A, B and C: At altitudes above 2 km,
contact Danfoss regarding PELV.
380-500 V, enclosure D, E and F: At altitudes above 3 km,
contact Danfoss regarding PELV.
525-690 V: At altitudes above 2 km, contact Danfoss
regarding PELV.
®
MG33BE02 - VLT is a registered Danfoss trademark
1. Power supply (SMPS) incl. signal isolation of U
indicating the voltage of intermediate DC Link
circuit.
2. Gate drive that runs the IGBTs (trigger
transformers/opto-couplers).
3. Current transducers.
4. Opto-coupler, brake module.
5. Internal inrush, RFI, and temperature
measurement circuits.
6. Custom relays.
7. Mechanical brake.
7
5 4 1
6
a
WARNING
,
DC
3
M
2
b
43
3 3