1. Laminated tп; b) ribbon tл

Table 2.1 – The suggested parameters of magnetic core

Magnetic core		Frequency, Hz	Parameter of magnetic core		Total power in the secondary winding P2, VA
type	material				150…300	300…1000	1000…2500
ШЛ ШЛМ shell-type	3411 Δ = 0,35	50	BS, T		1,65	1,65	-
			j, A/mm2		2,4-2,3	2,3-1,8	-
			k0	U0 = 100V	0,32-0,34	0,34-0,38	-
				U0 = 102…103	0,27-0,3	0,3-0,33	-
ПЛ ПЛМ ТЛ ribbon- type	3411 Δ = 0,35	50	BS, T		1,6	1,6	1,6
			j, A/mm2		3,0-2,4	2,4-0,35	1,7-1,4
			k0	U0 = 100V	0,29-0,3	0,3-0,35	0,35
				U0 = 102…103	0,25-0,3	0,3	0,3

The choice of magnetic core type is finished if the chosen type can contain the necessary windings with aperture occupation ratio by k_M 0,25…0,35.

For the chosen magnetic core of transformer from the table 2.4 it is defined the values of flux density B_m, current density in the windings j, aperture occupation ratio k₀ and material of magnetic core. When the material of magnetic core and its construction are defined from the table 2.5, it is used the value k_c that is the space factor of cross-section S_c by steel to define the width of ribbon.

The developed transformer contains S number of leg on which the windings are placed. The windings placement is defined by the coefficient k0. When S=2 the windings are placed on two legs of transformer and the coils are connected sequentially. In this case for bridge scheme will be K₀ = 0,5 and for other ones K₀ = 1.

Table 2.5 – Construction parameters of magnetic core

Construction of magnetic core	Isolation of bar or ribbon	Aperture occupation ratio kc when the width of steel is Δ = 0,35
Plate	Dope Phosphate film	0,9 0,94
Ribbon	Dope, enamel	0,93

When the calculation is done all results have to be shown in the table 2.6.

Table 2.6 – Parameters of transformer

Type and material of the core	Bm, T	j , A/mm2	k0	kcs	S	K0
Values

3. The calculation of the electrical parameters of rectifier

The calculation of the open circuit rectifier is defined by the formula:

(2.9)

where K₁, K₂ = m and K₃ are constant coefficients, whose values are given in the table 2.7.

The value of remainder voltage on the valves U_пр is given in the guide [13,16]. In the case when for the valves it is used germanium semiconductor diode, then U_пр is 0,5 V, for the silicon diode it is 1 V. To indentify the number of valves N it is necessary to take into account only the numbers of valves in one accept not total number of them.

On this step of calculations we can’t identify the number of voltage drop on the throttle’s active resistance of smoothing filter, that’s why we calculate its oriented value with respect to the value of P₀ according to the following formula:

U_D = K₄ · U₀, V (2.10)

where K₄ is the constant coefficient, whose value is given in the table 2.8

Table 2.7 – Calculating coefficients of rectifiers’ scheme

Rectifier’s scheme Coefficients	Single phase single-step (fig.2.2, a)	Single phase double-step (fig.2.2, b)	Three phase single-step (fig.2.2, c)	Three phase double-step scheme of Larinov (fig.2.2, d)
kr k1 K1 K2 K3 K5	7 5,5∙10-3 1 2 1 3,14	5,2 6,4∙10-3 1 2 2 1,57	6,6 3,3∙10-3 1 2 1 2,1	2,5 1∙10-3 1 2 1 1,05

Table 2.8 – Approximate values for coefficient K₄

Values P0, W	K4 (for fc = 50 Hz)
10…30 30…100 100…300 300…1000 1000…3000 3000…10000 10000…30000	0,2…0,14 0,14…0,1 0,1…0,07 0,07…0,05 0,05…0,035 0,035…0,25 0,025…0,018

All results have to be shown in the table 2.9.

Table 2.9 – The parameters of rectifier’s scheme

Calculated units	rm, Ω	LS, H	U0x,V
Results of calculations

According to the found value U_0x it is possible to refine the value of reverse voltage on diode for the chosen scheme according to the following formula , where K₅ is chosen from the table 2.7 and it is checked the type of valve. When the value of reverse voltage is more than 0,8U_{обр доп} , then it is necessary to recalculate.