Inductive elements are also called self-inductive elements. If the magnetic flux generated by each coil of two or more coils intersects with the other coil, these coils are said to have magnetic coupling or mutual inductance. (mutual induction). If these coils are assumed to be stationary, and the resistance in the coils and the distributed capacitance between turns are ignored, the coils with magnetic coupling can be expressed as idealized coupled inductors, referred to as coupled inductors [1] .
If the two coils
If the medium around the coil is a non-ferromagnetic substance, the self-inductive magnetic chain is
Mutual inductance magnetic link is
In formula (2),
with
It is called mutual inductance, abbreviated as mutual inductance, and its unit is Heng (H). can prove,
, Omit the subscript of M. M is often used to indicate the mutual inductance of two coupled coils. Thus, when
with
When flowing into coils 1 and 2 at the same time, as shown in Table 1 (c), the magnetic flux of coils 1 and 2 is taken from the direction of the inductive flux.
Table 1 Two coils with magnetic coupling
The directions of the mutual and magnetic flux linkages on a coil are not necessarily the same. As shown in Table 2 (a),
Mutual inductance flux when flowing out of terminal 2 of coil 2
Magnetic flux
The directions are opposite; as shown in Table 2 (b), when the winding direction of coil 2 and the winding direction of coil 1 are opposite, the magnetic flux linkage is mutually inductive.
Magnetic flux
The opposite direction. At this time
Table 2 Orientation of the magnetic flux
Eponymous end
In formula (4), the positive and negative sign before the mutual inductance voltage depends on the direction of the mutual inductance magnetic flux and self-inductance magnetic flux on one coil, and it is not only related to the reference direction of the current, but also to the winding direction of the two coils. Since the actual coil is sealed, it is difficult to know its winding direction; even if the winding direction is known, it is not convenient to draw the coil winding direction in the circuit diagram. To this end, the concept of the same-named terminal is introduced. When two currents are passed in, the two terminals that can make the mutual inductance magnetic flux and the self-inductive magnetic flux in the same direction of the same coil are called the same-named terminal , and are represented by " · " or "*". As shown in Table 1 (c),
Flows into terminal 1 of coil 1 and produces
with
;
Flows into terminal 2 of coil 2 and produces
with
,
versus
(or
versus
) In the same direction, so the terminals 1 and 2 through which two currents flow are the terminals with the same name.
Judgment of the same name
due to
with
In the same direction,
with
In the same direction, when the two magnetic currents generated when the two currents are passed in are the same direction, the two terminals that pass the current are the terminals with the same name, otherwise they are different ends. As shown in Table 22 (b),
Into terminal 1 of coil 1,
The magnetic flux generated by each of the terminals 2 flowing into the coil 2 is reversed, so terminals 1 and 2 are different ends, that is, 1 and 2 ' are the ends of the same name. The coils shown in Table 1 (c) and Table 2 (b) are available respectively. Table 3 shows the circuits shown in (a) and (b).
Use the same name terminal to determine the polarity of the mutual inductance voltage
After calibrating the terminal with the same name, the polarity of the mutual inductance voltage can be easily determined. It is defined by the terminal with the same name. Two currents flow into the terminal with the same name. The mutual inductance magnetic flux on a coil is in the same direction as the self-inductance magnetic flux. The positive sign is given before the mutual inductance voltage in equation (4). The mutual inductance voltage on the same-named terminal of the other coil is positive. As shown in Figure 1,
Into the same name terminal 1, the mutual inductance voltage
Positive polarity on end 2 of the same name, ie
This way, when
versus
,
versus
Take the correlation reference direction,
with
When the same-named terminal is taken as the positive polarity, the self-inductance voltage and the mutual-inductance voltage are both positive-polarity on the same-named terminal. In the formula (4), the mutual-inductance voltage has a positive sign [2] .
Table 3 Circuits with the same name
Figure (a)
Figure (b)
Figure 1 Using the same name terminal to determine the polarity of the mutual inductance voltage
