1.14.2. Operation of the half-wave rectifier with center tap and opposite-emf and active-inductive load

Conditins: =0, L_d, L_a=0;

1) 0Ld < 

2) Ld = 

.

Then

Figure 1.48

Thus, presence of opposite-EMF in the load circuit results only to changing of average rectified current.

Operating of a rectifier with opposite-EMF in the load circuit with Ld =  does not differ from operating with active-inductive load as, following to the theorem of indemnification, it is possible to consider and to replace E₀ by equivalent resistance .

2. Dependent inverters

2.1 Transition from a rectifying conditions to an inverting conditions

i_V1

E_дв

- +

+ -

M

TP

I_d

Е_г

i_V2

VS2

^о

~ U₁

_о

VS1

L_a

e_1a

e_2b L_d

L_a

Figure 2.1

The direct-current machine is included in the load circuit. It operates either a motor is having an electromotive force Е_mot or a generator is having an opposite electromotive force E_gen.

External characteristics are same as with R - L -load for L_d=∞, i.e.

The addendum E_d0 cos(α) will increase if α decreases and U_dα may take up negative values.

When

when

δ - an angle of restoration of locking properties of a thyristor when the thyristor is across an inverse voltage;

β - a commutation delay angle the inverter, or an advance angle.

β = 180˚ - α

As U_dα and I_d are opposite direction, U_dα interferes flowing current I_d by inverter conditions.

Instantaneous power of a secondary winding is

.

During the most part of the period P₂(υ) is negative;

The mean or active power for this reason also is negative.

The mean power across a circuit of a rectified current is also negative.

It means that in inverter conditions the power is delivered by the direct-current circuit to the ac-circuit. Thus a flux of active power changes direction at conversion from rectifier duty into an inverter duty. Thus there is not a rectifying, but it is inverting of a current. Energy is transferred by the direct-current circuit to the ac-circuit.

The inverter witch supplying the ac-circuit, names to as dependent inverter, because EMF of network enters into a contour of current commutation from the thyristor to the thyristor. The moment of switching on of a thyristor would depend from a commutation delay angle α (or β) which delays from the point of natural switching on thyristors which is determined by EMF of networks and a converter connection.

U,i U uV1 δ π 2π γ γ β α uV1 β iV1 Id U,i U γ γ 2π π α α α iV1 Id

Figure 2.2