When modern converters are used in the domain of drive technology, every application involves different challenges and may require different or additional components in order to counteract interfering phenomena such as EMC problems harmonic ripple voltage spikes short-circuit currents interference currents and to meet the demands of the current EMC and power quality directives for clean energy networks, without restricting efficient plant operation. Apart from the above interfering phenomena, undesirable side-effects require a solution, as for example when a motor is started or slowed down, starting currents have to be attenuated and excess energy dissipated.
REO offers suitable solutions for both simple and demanding applications in the field of converter and drive technology, and has the expertise to develop solutions that meet individual requirements.
In general power supply units are built up with a rectifier followed by a filter capacitor. Such a construction takes its energy from the supply network in just the maximum of voltage. The current that flows consists of short-time peaks and includes a high portion of harmonics. According to the requirements of a new standard these disturbances must not exceed certain limit values.
A line commutation choke will relieve the supply network by compensating the harmonics reactive power. The harmonics will be strongly reduced. The very high current peaks due to the principle of function of the rectification will be attenuated by more than 60 % by the inductance.
The line choke will more over limit the disturbances coming from the mains such as current peaks and voltage drops. This kind of disturbances which are caused by switching actions or shorts to earth may considerably influence electrical devices.
Every country sets limit values on harmonics to ensure that electricity consumers don't overload the public supply networks with them. The harmonics concerned are generated by devices carrying up to 75 A in the frequency range 0 to 2 kHz. EN 61000-3-12 significantly calls for a 40% limit on THD (Total Harmonic Distortion) in the fifth harmonic. If converters are used without filters, their interference spreads throughout the network, although the effects may not be immediately apparent. If more and more converters are used, a wide variety of phenomena may occur as the interference they generate mounts up. The scope of the effects ranges from network imbalance or network failure being reported by a wide variety of devices, to damaged transformers. Which phenomena occur depends on the structure of the network.
Radio-interference filters are a combination of several, usually passive, electronic components that attenuate the useful low-frequency signal as little as possible while attenuating unwanted high frequency interference signals as strongly as possible.
REO filters are available as complete units ready for installation, or they can be mounted, usually at lower cost, on the same circuit board as the noisy device.
Mode of operation of standard EMC filter range of EMC filters:
150 kHz-30 MHz range of effectiveness of EMC filters: 10 kHz-30 MHz
The conventional output choke has a very good storing behaviour. The choke has the effect of a typical series inductance and smoothes the symmetrical actual current and the asymmetrical parasitic current. The voltage rise is limited to less than 500V/μs. The voltage peaks of the voltage between lines on the motor terminal board are lower than 1000V. This solution attenuates the cable-conducted disturbance very well even in the lower frequency range. The electromagnetic radiation of the lead is considerably attenuated. Losses and typical motor noise, caused by harmonics, are reduced.
Commutation (current conduction between thyristors) for fasts witching semi conductors, PFC (Power Factor Correction).
Sine wave creation of the output current on the output of a frequency drive. Longer lifetime of motor insulation, noise reduction.