Minimizing harmonic pollution of the public electricity supply is an issue, which, with good reason, is being given more and more attention. John Symonds of REO UK Limited examines why harmonics are an issue, and explores some of the options available for harmonic control.
As current rises, EMC conformance and system protection becomes more costly and the choice of solutions diminishes. Installers, panel builders, systems integrators and drive suppliers not only have to conform to European Union Directives and G5 / 4 but also have to consider protection against surges and ride-through.
REO (UK) has reported a sales surge in its range of REO-MED medical isolation transformers, which it puts down to the medical industry's preparation for the new EMC standard that comes into play in November 2004. The introduction of this tighter standard for medical equipment has been driven by the proliferation of wireless devices by legitimate users in hospitals.
From November of this year, all medical electrical equipment and systems supplied in the EU must comply with a tough new electromagnetic compatibility (EMC) standard - EN 60601-1-2: 2001. John Symonds of REO UK examines the need for this standard, discusses its implications, and provides guidance on meeting its requirements.
REO (UK) Ltd is now supplying a range of REO-MED medical isolation transformers, which provide an ungrounded power supply system that improves the reliability of the supply voltage and reduces the leakage current. This effectively eliminates the potential for high touch voltages on the connected equipment.
Inverters produce harmonic rich currents on the mains supply side, which increases the I2R losses in the supply transformers and causes additional heating. Furthermore, the high frequency current components also cause heating because the inductive reactance is frequency dependent. The problem is made greater by the “skin” effect ”forcing the current to flow in the outer surface of the conductors.
Installers of AC variable speed drives are now faced with a myriad of confusing technical issues about filters and ancillary equipment. REO UK has therefore issued a new free technical guide called “Application Notes for Drive Engineering”, which is now available. The guide provides beneficial information about avoiding and overcoming everyday, power quality problems associated with variable speed drives.
REO UK Ltd, the manufacturer of power quality and power management equipment has introduced a new range of high current transformers. The new units are based on the current transformer principle with single or multiple secondary turns. The range produces an output voltage of either 1.67 or 0.8V with output current ranging from 500 to 5000 A. They are suitable for use in test generators for power frequency magnetic fields immunity tests as specified in EN 61000-4-8: 1993. REO also manufactures the variable transformers that are used as voltage regulators
REO has produced its largest ever braking resistors to absorb the surplus energy generated by lifts and escalators during their people laden descents. These new products, specific only to REO, are sealed to IP64, so can withstand extremely dusty and damp environments and are suitable for outdoor use.
REO UK has released a new detailed guide, which provides information about various types of transformers and their applications. The Transformer Guide also details the theory, functions and actions of transformers and gives an overview of their history and the future.