The new current transformers from MAGNETEC, featuring NANOPERM® alloy core for high-precision readings plus improved tamper-proofing, can be combined with MAGNETEC’s magnetic shielding designs to form an ideal system solution for a broad range of anti tampering metering applications. The combined advanced features of both current transformer and adapted magnetic shielding offer a so far unique anti tampering performance for the smart metering global market.
The tampering issue seems to have gained more and more interest in many regions of the world. Former IEC standard 1036 which is now 62053-21 required 0,5 mT. For this test condition it was experienced that it should be not so serious with the types of cores used. They are proven to have a very low sensitivity against external magnetic fields. One has to approach the magnet to a distance less than 3 mm to the winding to influence the output signal where the direction of magnetization radial to the core is the most critical.
The new combination of current transformer including magnetic shielding prpvides an excellent new opportunity to supply complete solutions with high quality to the global market for smart energy meters. The new current transformer series, especially for 60 A and 100 A metering devices in particular can now compete on a cost basis with all other widespread transducer systems such as Hall-effect transformers, Rogowski systems or shunts.
It is one of the most up-to-date topics within the Solar Power Industry to improve the efficiency of that complex process of energy conversion. Every single tenth of a percent is welcome – although > 90 % is already state-of-the art for modern DC/AC converters.
Following this target, more and more producers of photovoltaic inverters are currently replacing standard components by high tech solutions providing the best possible electrical efficiency. One of those examples are the chokes in the EMI filters on both, the DC and the AC lines.
Nanocrystalline cores offer a permeability being five times higher than ferrites which results in significantly smaller build volume and – as a consequence – the copper resistance is reduced significantly, too – typically by about 50%!
It is a realistic option, to replace an existing 2-stage EMC filter based on conventional Ferrite chokes by a single-stage solution based on a nano-choke, which provides a similar attenuation but with lower losses.
We would like to thank your for visiting our booth during Nov. 9-12.
It was a great event where we met so many customers and friends and furthermore, plenty of new contacts have been established.
See yo again latest in 2012 – same time same place!
For AC-type RCCBs that are sensitive to sinus exciting currents, toroidal cores made of Permalloy-type materials are used for decades. The application of nanocrystalline alloy NANOPERM in RCCBs were limited to a region where the special annealing cycle leads to flat or round ferromagnetic hysteresis loop with a remanence ratio smaller than 0,7 with a maximum permeability less than 250 000. The actual trend – for technical as well as for cost reasons – is to make magnetic cores much smaller than their existing counterparts with extremely high permeability. This reveals a new generation of extremely small toroid soft-magnetic cores that can be used in AC-type RCCBs with the following exceptional properties:
- the magnetic core weight can be reduced down to 40 – 70 % compared to the Permalloy-type cores for similar applications
- the maximum permeability is at least 400 000 for typical applied maximum magnetic fields of Hmax = 7 – 20 mA/cm
- the output voltage ratio measured between magnetized and demagnetized states is at least 3 times better for small maximum magnetic field of Hmax = 4 mA/cm than for Permalloy-type cores
- the temperature variation of the permeability at the operational magnetic field is between 80 % and 120 % compared to room temperature (20±5 °C) for temperatures between –25 °C and +100 °C
- the remanence ratio is bigger than 0,7.
So far, nanocrystalline cores could not be used in applications with significant DC preload because they saturate early due to their high permeability level (> 18.000), which gives only an advantage in non DC applications.
MAGNETEC now offers high saturation cores which enter into a low permeability range of typically 2.000-8.000 which was not available so far.
Those cores are very much advantageous in EMC filters for applications with a high amount of asymmetric interference current (e.g. inverter drives) concerning build volume and/or attenuation performance compared to the established Ferrite materials. The reason for that is, that the nanocrystalline core material NANOPERM LM (low my) offers three times as much saturation flux density at the same level of permeability.
Another field of application are precision Current transformers for household energy meters which are currently equipped with very expensive cobalt-amorphous cores. Here, the new material offers a significant cost advantage.
The new cores of the NANOPERM LM series were first time offered to public during this year’s PCIM in Nuremberg in May.
The new COOL BLUE range completes MAGNETEC’s series of high performance toroids made from the nano-crystalline material NANOPERM. Available are cores up to 500 mm (!) outer diameter and several space saving stadium-shaped (oval) variants.
The cores of the new series feature significantly improved high frequency performance due to a permeability level several times higher than any kind of ferrite. In Europe, COOL BLUE cores are being used increasingly to reduce damaging bearing currents of modern inverter systems of the latest generation (doubly fed induction generators (DFIG) IGBT technology) from apprx. 500kW up to about 5 MW. As a consequence of those parasitic currents, the bearings corrugate followed by electrical breakdown of the lubrication which soon causes an early failure and standstill of the whole motor. The same effect occurs in modern wind energy generators, even though the direction of the energy flow is reversed in this application. Some of the leading European Wind Turbine manufacturers have successfully designed in the new COOL BLUE cores recently because it is technically the most effective and proven solution to a severe problem and provides the best value for the money at the same time. The COOL BLUE solution is significantly cheaper than isolating hybrid bearings.
With those high-tech cores not only the over voltage peaks at the winding terminals are significantly reduced, but also the asymmetrical EMI currents which both are generated by the parasitic capacities of the interconnecting cables and the motor/generator itself.
In order to achieve an efficient reduction of those destructive effects, several nano-crystalline cores of suitable geometry have to be put commonly over the connector cables each in the DC-link and/or at the inverter output. In this configuration, the cores operate as common-mode chokes. This method significantly increases the service life of the generator bearings and thus significantly reduces maintenance costs and costly standstill periods.
Summary of the advantages of COOL BLUE cores:
- most efficient solution for motor/generator bearing protection above 500kW
- by far the best value for the money compared to expensive ceramic bearings
- can easily be re-tooled/added to extisting installations
- is a proven solution due to many thousands of installations in Europe.
Several of the leading European Wind Mill manufacturers have been convinced by the concept of COOL BLUEand they have introduced this method as their standard for generator bearing protection.