Støy og valg av transformator
https://www.parasound.com/pdfs/JCinterview.pdf
Q: What can you tell us about the transformers? Are they very important?
JC: Absolutely, but when we talk about transformers we have to separate
power amps and preamps. While they are not perfect, Toroidal
transformers are the logical choice for power amplifiers because they are
very efficient, they tend to have a fairly low hum field, and they’re readily
available in large power ratings.
For preamplifiers and other line-level components, the old type EI
transformers or what’s called a D-core or split C- core transformer is
actually better than a toroid. First of all, they tend to be more compact, and
second, and perhaps more importantly, they have very low capacitance
between the windings.
This can be a problem when Toroids are used in low signal level
applications; the windings are on top of each other so they talk to each
other. It used to not be so bad but today the AC power is so dirty.
Harmonics that are created by high frequency fluorescent lights, fax
machines, computers, you name it. All this new stuff, that’s only been
around for maybe the last 10 years, tends to get into the power supply
through the transformer and then in to he grounding system and
ultimately into our sound system. So then people have to of course use
expensive power conditioners to repair the problem but if you fix it in the
first place then its not so important.
Q: So how would you fix it in the first place?
JC: By using a transformer that isolates the winding, which is important on
low level circuits. The old style EI or the new C- or D-core is the ultimate
in that respect -- as long as it is a dual-bobbin winding with physically
separate bobbins for the primary and for the secondary. It makes a big
difference in sound quality.
In power amplifiers, however, that isn’t as important because the
levels are just so much higher. If we had a choice, and if money was not
involved, or weight, or anything else, we’d probably use an EI type or
special type of transformer.
https://www.spec-corp.co.jp/e/audio/RSA-M99/index.html
SPEC sticks to the R-core transformer.
The R-core transformer brings out a dynamic and powerful sound.
This same transformer is being used in the top of the range model.
R core transformer_James transformer-custom toroidal transformer|R core transformer|O core transformer|C core transformer|EI transformer
R core transformer has high isolation degree. it can improve the signal-to-noise ratio, isolate the harmonic interference, reduce the noise, make he background cleaner. R core transforer can fully improve the quality of sound.
https://www.indiamart.com/powercontrolelectronics/industrial-transformer.html
Further the Leakage Flux of the transformer IS VERY LOW (about 1/10th of conventional transformers) which permits the equipment manufacturer to place the transformer close to critical electronic components.
The balanced winding & low leakage flux ensures LOW NOISE of the transformers. This gives a cutting edge to the transformer for use in Medical Equipment, Audio & Video amplifiers & other noise sensitive equipment.
Small size and weight: R-core transformer is made using no cut, high degree silicon steel strip. Consequently, its size and weight is 30% smaller and 40% lighter than EI transformer respectively.
Og i distribusjonsnettet
https://pdfs.semanticscholar.org/8aa1/4c4f15dd6c151717193c083fca320dd652d9.pdf
The analyses presented in this paper show various benefits of transformers featuring
triangular wound cores: low no-load losses, reduced EMC relevant magnetic stray fields and
improved harmonic behavior are advantages of these transformers compared to planar stacked
core transformers of corresponding ratings.
https://www.powerelectronics.com/content/power-transformer-attenuates-harmonics
Med bl.a en god del om Plitron`s balanced power, Narrow Bandwidth Technology som brukes av bl.a Torus,Bryston etc
These extra signals, called noise or distortion, appear in two ways on the power lines. At frequencies above 1 MHz, noise is mostly common mode, which refers to both line and neutral containing an equal amount of amplitude and phase distortion. For frequencies below 1 MHz, the major component of the noise is typically differential mode, where the noise on line and neutral sides is equal in amplitude and opposite in phase. Differential-mode noise generates a real noise voltage difference between line and neutral.
Ironically, the same equipment that generates this distortion demands clean power to operate. Modern electronic equipment depends on a low-distortion voltage supply to operate to spec, and there is high sensitivity to fluctuations and transients. In addition, large pulsating currents can cause flat topping of the voltage waveform. Noise can be introduced into susceptible cables or other components from high-frequency circulating currents, causing havoc with microprocessors and other sensitive components.
Common Solutions to Attenuate Noise
Therefore, for optimum attenuation, the impedance of the filter should be low as well. In reality, however, this would require impracticably large and expensive capacitors and inductors.
A more practical approach is to start filtering noise at frequencies above 1 kHz, where most of the unwanted noise is found and where such interference causes malfunction of electronic equipment. The filter should be of the low-pass type with second- or higher-order slopes. The internal capacitance and inductance inside the transformer are the tools to create the desired filter
On installations where attenuation of high frequencies are not demanded but deemed as performance enhancements, such as in audio systems, a common noise reduction system on the market is balanced power
Most harmonics originate from the generation of harmonic currents caused by nonlinear load signatures. A nonlinear load is characteristic in products such as computers, printers, lighting and motor controllers, and much of today's solid-state equipment. With the advent of power semiconductors and the use of switching power supplies, the problem has become more severe in the last few decades. Most of these products didn't exist 30 years ago, thus the trouble is recent and a direct result of technological innovation.
A nonlinear load draws current in a non-sinusoidal manner, despite the fact the voltage may be perfectly sinusoidal (Fig. 1). Nonlinear loads draw current during a portion of the incoming voltage waveform, not continuously as with a light bulb. Current is drawn in bursts or planned abrupt pulses, as required by the product. The result is distorted current wave shapes, the harmonic content of which can flow back and contaminate other parts of the power supply
Another common solution is the use of K transformers. Basically, a K transformer is a transformer built with any excessive temperature rise calculated strictly on I2R losses. IEEE provides a formula to calculate THD and then derive a K number. At that point, it's simple for the transformer designer to understand the nature of the thermal issues as a result of harmonics and design accordingly. Use of multistranding will assist with heating from skin effect.
Plitron has developed the means to accurately calculate specifications and to construct transformers to meet specified corner frequencies. NBT reduces line distortion within isolation or power transformers.
An NBT transformer performs as a low-pass filter with a selected corner frequency. The system is based on two principles that involve an increase of the internal series inductance and the phase cancellation principle.
Har syslet litt med filtre
med filter tunet til 5kHz,0,290V
sammen med PS Audio NH,tunet til ca. 10kHz,0,350V,
sammen med filteret for 1150Hz,23nd harmoniske,0,250V,
målt over L på filteret tunet til 5kHz.
Igjen,NH forsterker forsterker problemet i området til filter tunet til 5kHz,
men det som er snodig er at filteret for 23nd harmoniske er med på å dempe
spenningen over L i filteret tunet til 5kHz.
Spennende,får noe å bruke ledig tid på utover høst/vinter,
spesielt når spenningen over L av og til blir pulserende
til litt over 1V og ned igjen,relativt sakte opp og ned.
