In an isotropic homogeneous magnetic medium, b is proportional to h:
B=μH
μ is called the permeability of magnetic medium μ=B/H,
The permeability of magnetic medium is μ=μ0( 1+χm).
The relative permeability of magnetic medium μr =( 1+χm)
Is the ratio of b to h at any point on the magnetization curve. Magnetic permeability actually represents the difficulty of magnetization of magnetic materials. At different stages of magnetization, the permeability of materials is also different, and the highest permeability is called the maximum permeability. The magnetic permeability at the starting point of magnetization is called initial magnetic permeability, or initial conductance for short. Magnetic permeability is another very important index of soft magnetic materials. Relative initial permeability μi is defined as
In SI, the unit of permeability is per meter henri (H/m), usually T/(A/m) and T/(A/cm), but it is generally expressed by relative permeability μ r ..1(h/m) = t/(a/m) =100t/. In some data, we use T/Oe or Gs/Oe. Gauss and Oster are both former physical quantities. 1T= 10000Gs, 1A/m=4πe-3 Oe, and the relative permeability of the magnetic medium with the permeability of 1Gs/Oe is 1. Relative permeability μr is a dimensionless quantity.
Iron loss angle psi
To make a magnetic material have magnetic induction intensity B, it is necessary to have magnetic field intensity H. For alternating current, magnetic induction intensity B is not synchronous with magnetic field intensity H, and magnetic induction intensity B always lags behind magnetic field intensity H, and the lag angle is the iron loss angle. Permeability and loss angle are not constants, which can be found by magnetization characteristic curve of iron core. In the normal working range of current transformer, the greater the magnetic induction intensity B, the greater the core loss angle.
Rated current of current transformer
Rated current means that it can work for a long time without being damaged. The rated input and output currents are called rated primary current and rated secondary current respectively, and the ratio of rated primary current to rated secondary current is called rated current ratio, which is expressed by Kn. Users are usually concerned about the rated current. In the miniature current transformer, the nominal current is as follows: 5A/2.5mA means the rated primary current 5A, the rated secondary current 2.5mA, and the rated current ratio is 2000. Rated current is the main basis for designing small current transformers.
Current transformer ratio difference
The ratio difference is also called the ratio difference: the ratio difference is the difference between the secondary current and the actual primary current converted into the theoretical secondary current according to the rated current ratio, which is expressed as a percentage of the latter. For uncompensated miniature current transformers, the ratio difference is negative.
f =(I2-I 1/Kn)/(I 1/Kn)× 100%
F ratio difference%
I2- secondary current a
I 1- primary current a
Kn—— Rated current ratio
Angle difference of current transformer
Angular difference is also called phase difference: angular difference is the phase difference between the secondary current and the primary current, which is usually expressed by a minute ('). The phase difference before the primary current is positive, and vice versa. For uncompensated miniature current transformer, the angle difference is positive.
Inductor inductor
All components that can generate inductance are collectively called inductance. Inductors are generally composed of coils, so they are also called induction coils. In order to increase the inductance and Q value and reduce the volume, a soft ferrite core is usually added to the coil. Inductance is divided into fixed inductance and adjustable inductance (trimming inductance). Fixed inductance is generally marked with color code or color ring, so it is also called color code inductance. Due to the requirements of miniaturization and production automation of the whole machine, inductors have developed in the direction of SMD.
inductance
When the current in the coil changes, the magnetic flux generated by the changing current in the coil loop itself also changes, so that the coil itself generates induced electromotive force. Self-inductance coefficient is a physical quantity that represents the self-inductance ability of coil. The self-inductance coefficient is also called self-inductance or inductance. L, in Henry (h). One thousandth of them are called milli-hens (mH), one millionth are called micro-hens (μH) and one thousandth are called Nahen (NH).
quality index
Quality factor Q is a factor used to measure the relationship between the energy stored in an energy storage element (inductor or capacitor) and its loss energy, which is expressed as: Q=2π maximum stored energy/cycle dissipated energy. Generally speaking, the larger the Q value of the inductance coil, the better, but too large will make the stability of the working circuit worse.
Self-resonant frequency
Inductor is not a pure inductance element, but also contains a distributed capacitance component. The resonance of a certain frequency caused by the inherent inductance and distributed capacitance of inductance itself is called self-harmonic frequency, also known as * * * vibration frequency. It is expressed in S.R.F and the unit is megahertz (MHz).
DC resistance movement (DCR)
The resistance of inductance coil measured under non-alternating current, in the design of inductance, the smaller the DC resistance, the better, and its measurement unit is ohm, usually marked with its maximum value.
Impedance impedance
The impedance value of an inductor refers to the sum (complex number) of all its impedances under the action of current, including AC and DC parts. The impedance value of DC part is only the DC resistance (real part) of winding, and the impedance value of AC part includes reactance (imaginary part) of inductor. In this sense, inductance can also be regarded as "AC resistance".
rated current
The intensity of continuous DC current allowed through the inductor is based on the maximum temperature rise of the inductor at the maximum rated ambient temperature. The rated current is related to the inductor's ability to reduce winding loss through low DC resistance, and also to the inductor's ability to dissipate winding energy loss. Therefore, the rated current can be increased by reducing the DC resistance or increasing the size of the inductor. For the low frequency current waveform, the root mean square current value can be used instead of the rated DC current, and the rated current has nothing to do with the magnetism of the inductor.