1, what is leakage feeling

 

Leakage feeling is electric machinery the first time class leaks in the process of coupling that partially magnetic flux.

 

The lines of force that the leakage induction of transformer should be coil place generation cannot pass secondary coil, because this produces the inductance of leakage magnetism,call leakage move.

 

Is leakage feeling in? Although printed circuit board the one part that the prints lead and transformer down-lead end that go up also is leakage feeling, but major leakage feeling is in winding of side of transformer former side, especially in the winding of former side side that those and winding of deputy side side have coupling to concern.

 

 

Because a group of coil go to transformer,leakage feeling is another group of flux are not complete coupling and the inductance heft of generation. Any primary coil do not have the ministry branch of coupling to show a perceptual impedance with primary series connection to secondary coil flux, because this is in principle graph, leakage feeling expresses to be in ideal transformer primary coil front and the inductance outside.

 

In specific applying, be like switch power source and illume commutator, the leakage feeling of transformer can produce main functional effect in products plan. Accordingly, accurate leakage feeling is measured to transformer manufacturer it is an important step normally.

 

Ideal transformer

 

Theoretic ideal transformer does not have loss. Electric pressure ratio is v/LIT all over the ground number to compare directly, the reciprocal that voltaic comparing compares for v/LIT all over the ground number (graph 1) .

 

 

Actual transformer

 

In actual transformer, the certain flux of primary coil won’t coupling arrives secondary coil. These “ leakage drop the flux of ” to won’t share the work of transformer, can express to be the additional perceptual impedance that establishs ties with coil (graph 2) .

 

 

Actual transformer adds air space

 

In the design of certain transformer, leakage feeling must want to hold larger proportion in total inductance volume, and set a small error. Leakage feeling quantity is proportional increase to come true normally through air space introducing in magnetism core, reduce the inductance of the magnetism conductance of magnetism core and primary coil consequently. Because of primary coil and this secondary coil flux not the proportion that coupling part place holds also can increase (graph 3) .

 

 

So whether does air gap have linear concern with leakage feeling?

 

3 kinds of concerns of transformer leakage feeling and air gap size show below with an example: Changeless, greaten, decrescent.

 

See figure below, hypothesis air gap 1, 2, 3 make magnetoresistive R1=R2=R3, that little part magnetic flux of oversight window, knowable

 

Φ=Φ1+Φ2.

 

 

Below existence 3 kinds of circumstances:

 

1, increase air gap 1, r1>R3, make Φ1>Φ2, namely coupling arrives the magnetic flux of Ns is more, leakage feeling is reduced.

 

2, increase air gap 2, r1=R3 still holds water, Φ1=Φ2, namely coupling arrives the magnetic flux of Ns is changeless, leakage feels changeless.

 

3, increase air gap 3, r1<R3, Φ1<Φ2, namely coupling decreases to the magnetic flux of Ns, leakage feeling increases.

 

The relation of transformer leakage feeling and air gap size, cannot say simply to increase, reduce or changeless, get the winding structure with particular basis, magnetism core structure will analyse.

 

Decide the element of leakage feeling size

 

To the fixed transformer that has made, leakage feeling and the following elements concern:

 

K: ? Direct ratio of? of chart Gan stool feels at leaking, to simple winding and 2 winding, take 3, if 2 times winding and winding crisscross are circled,make, so, take 0.85, why do this recommend sandwich to circle the account that controls a method namely, leakage feeling drops very a lot of more, still do not arrive to original 1/3 probably.

 

Lmt: ? Chang of Qiang of Quan of garden of sip of   Pu lifts? of ざ of Xun Mou of arrogant  throat so, transformer architect likes to choose the magnetic core with magnetic core long center pillar. Winding is wider, leakage feeling is reduced more. Control the v/LIT all over the ground number of winding in least degree, have profit very much to reducing leakage to feel. The influence that v/LIT all over the ground number feels to leaking is square relation 2.

 

Nx: ?  of pharynx of chart Lv head?

 

W: ? ? of Ji of chart a pavilion or house on a terrace a moment ago had said. Everybody can take a very common BOBIN to be analysed.

 

Tins: ? Pu whoop is  island Xi taken?

 

BW: ? Does chart Jie Mei seek Xi of dusk of Lv of chart of raw meat or fish of  of Liang of urinate a legendary venomous insect to take?

 

2, the harm that leakage feels and defend

 

Leakage feeling is to point to arrive without coupling magnetic core is other perhaps of winding measureable inductance quantity. It is strung together with respect to independent like inductance in circuit. When it brings about switch canal to close aiguille appears between DS. Cannot be circled by 2 side winding because of its magnetic flux catenary.

 

Leakage feeling can regard the parasitism inductance that inductance of side of as former as transformer side establishs ties. So, in switch the canal closes the instant, the electric current in these two inductance is Ipkp, namely electric current of peak value of former side side.

 

But, when switch canal closes, energy of inductance of former side side can change deputy limit through mutual inductance (through outputting diode) release, but nowhere can go to leakage sense energy.

 

 

Accordingly, it can come with tremendous voltage aiguille form “ abreacts complaint " . See a picture.

 

 

If do not endeavor to draw these leakage sense energy, aiguille will be very tall, will cause switch to since these energy cannot transmit deputy side side for certain,provide damage, that has two kinds of choices only: Or tries to pass on to capacitance losing a person, or tries to be used up (loss) . Simple for the purpose of, the option is normally latter. Can use stabilized voltage to be in charge of clamp directly commonly method, if plan institute is shown.

 

 

Of course, voltage of stabilized voltage canal must is in charge of according to switch can susceptive is the biggest voltage will choose to notice, stem from a few reasons (especially efficiency) , after had better establishing ties stabilized voltage canal and block diode, paralell connection is on winding of former side side, if plan institute is shown.

 

Additionally one kind of method is, the means that uses capacitance shunt resistance realizes RCD; The RCD pincers that uses a circumstance to be able to use simple easy implementation in major low power circuit comes aiguille of slow down voltage.

 

Because of this RCD clamp circuit with its concise Yi Shi shows multi-purpose Yu Xiaogong leads a circumstance. Graph 1 with the graph the 2 RCD clamp in stimulating circuit to turn over respectively the voltage of two end of circuit and capacitance C is undee.

 

 

Introduce RCD clamp circuit, the purpose is to waste leakage sense energy, but cannot use up advocate excitation inductance energy, can reduce circuit efficiency otherwise, because this designs the value that appropriate R and C should choose in debugging a process in circuit, drop leakage sense energy in order to make its just are used up. Its job principle will be analysed below.

 

When switch is in charge of Q to close, transformer is primary coil voltage is retrorse, with hourglass feeling LK releases energy to undertake charging to C directly, capacitance C voltage rises quickly, the C after diode D ends undertakes discharging through R

 

If C value is greater, the voltage on C is slow rise, deputy edge has been stimulated instead strong small, transformer energy cannot pass deputy limit quickly; If C value is extraordinary big, voltage peak value is less than deputy edge to reflex voltage, criterion clamp the voltage on capacitance will maintain all the time around voltage of deputy edge reflex, namely clamp resistor turns into laden, wasting magnetism core energy all the time, right now two upright weaveform are like capacitance graph (A) place is shown.

 

 

Capacitance two end are undee

 

If RC is too small, criterion capacitance C charges faster, and C will discharge very quickly through resistor R, energy of sense of the leakage in whole process is used up very fast, in the clamp before Q is enlightened the load that resistor becomes transformer, waste the energy that transformer stores, reduce efficiency, two end of capacitance C are undee if pursue (B) place is shown.

 

The value that be like RC takes a cost more appropriate, when to switch tubal Q debuts again, the voltage on C just puts capacitance to be close to at voltage of catoptric of transformer deputy edge, right now clamp the effect is better, two end of capacitance C are undee if pursue (C) place is shown.