What Are Noise Cut Transformers?
A noise-cut transformer is a device designed to prevent noise interference. It is a trademark developed by DENKEN SEIKI KOGYO K.K. in 1960 and is also called Isolation Transformers, although its common names are fault wave isolation transformers and transformers for noise suppression. Noise-cut transformers are a practical application of transformer-type noise prevention elements.
Since it separates and isolates the source of the noise and the electric circuit on the side disturbed by the noise, it is highly effective in preventing noise. Also, because it is a separate isolation type, it can function even in a poor electromagnetic environment.
Uses of Noise Cut Transformers
Many modern devices are high-speed and multifunctional, which makes our lives more convenient. Since these devices are operated by micro-voltages, they may malfunction due to noise entering from the outside.
Lightning, amateur radio, automobiles, discharge equipment, home appliances, and medical equipment are all subject to external noise intrusion. Noise Cut Transformers can prevent these noises, and the noise itself that they emit will not leak into external circuits.
Principle of Noise Cut Transformers
Noise Cut Transformers prevent noise from entering the secondary side. There are two types of noise: common mode and normal mode.
1. Common Mode
In the case of common mode noise, low-frequency noise (around several 10 kHz) can be somewhat attenuated by Noise cut transformers. However, as the noise frequency increases, noise penetration into the secondary side increases due to the capacitance between the primary and secondary sides of the transformer.
In this case, noise-cut transformers can prevent noise intrusion by adding an electrostatic shield between the primary and secondary coils and grounding it.
2. Normal Mode
Normal mode noise is output on the secondary side as it is, so the transformer itself has no suppression effect. For example, the frequency of noise caused by lightning is very high compared to the frequency of power supplies for general equipment (50/60 Hz).
By taking advantage of this, noise in the normal mode can be suppressed by having the filter pass through the lower frequencies of the power supply and weaken the higher frequencies.
Structure of Noise Cut Transformers
In addition to the structure of conventional isolation transformers, the structure of noise-cut transformers consists of multiple encircling electromagnetic shielding plates around the periphery of the coil transformer. In addition, the coil arrangement, core material, and shape are designed so that the magnetic flux of high-frequency noise does not interlock with each other. This prevents the transmission of noise due to capacitive coupling and electromagnetic induction.
When noise is to be cut, the usual measure is to isolate the source of the noise. The actual isolation measure is almost always a photocoupler on the circuit. If a photocoupler is not used, the method of dealing with the problem is a noise-cut transformer.
For cost and space reasons, it is preferable to use a photocoupler on the circuit board, but if a circuit board is not available, a noise-cut transformer is used. However, noise-cut transformers are not a panacea, and the secondary winding is also affected by noise from the primary winding. The use of noise-cut transformers can solve this problem.
Other Information on Noise Cut Transformers
Grounding of Noise Cut Transformers
Some measures can be taken to prevent noise, even in locations with different potentials between the ground of an electrical circuit and the earth, or in cases where grounding is not possible. One such measure is to install noise-cut transformers.
If this is still ineffective, ensure that the area where noise-cut transformers are installed makes contact with the ground over as large an area as possible. Another effective method is to make the input and output cables into shielded wires that can shield noise, and install this shielded wire and the case of noise-cut transformers over a large area. This is expected to improve the noise rejection effect.