6 Content Page 6 Protection against Electric Shock and Energy Hazards .............................................. 133 6.1 General ...................................................................................................................................... 133 6.2 Mains Supply System ............................................................................................................ 134 6.3 Additional Protection ........................................................................................................... 137 6.4 Fuses and Circuit Breakers ..................................................................................................
139 7 Mains Interference ....................................................................................................................... 142 7.1 What are Harmonics?............................................................................................................ 142 7.1.1 Linear Loads .................................................................................................................. 142 7.1.2 Non-linear Loads ......................................................................................................... 143 7.1.3 The Eff ect of Harmonics in a Power Distribution System .............................
145 7.2 Harmonic Limitation Standards and Requirements .................................................. 147 7.3 Harmonic Reduction Methods in Frequency Converters ........................................ 147 7.3.1 Passive Harmonic Mitigation .................................................................................. 149 7.3.2 Active Harmonic Mitigation .................................................................................... 150 7.4 Harmonic Analysis Tools ...................................................................................................... 152 7.4.1 VLT® Motion Control Tool MCT 31 .........................................................................
153 7.4.2 Harmonic Calculation Software (HCS) ................................................................. 153 8 Interfaces .......................................................................................................................................... 154 8.1 Human Machine Interface (HMI) ...................................................................................... 154 8.2 Operating Principles of Serial Interfaces ....................................................................... 156 8.3 Standard Serial Interfaces in Frequency Converters .................................................
158 8.4 Fieldbus Interfaces in Frequecy Converters ................................................................. 159 8.5 Fieldbuses Standardisation ................................................................................................ 161 9 Sizing and Selection of Frequency Converters ............................................................... 164 9.1 Get the Drive Rating Right .................................................................................................. 164 9.2 Rating of the Frequency Converters from Motor Specifi cation ............................
165 9.3 Overload Capacity ................................................................................................................. 166 9.3.1 Energy Effi ciency Concerns ..................................................................................... 168 9.4 Control Range ......................................................................................................................... 169 9.5 Derating of FC ......................................................................................................................... 170 9.6 Regenerative Energy.............................................................................................................
171 9.7 Motor Cables ........................................................................................................................... 172 9.8 Environment ........................................................................................................................... 173 9.9 Centralised versus Decentralised Installation .............................................................. 175 9.10 Examples ................................................................................................................................... 177