- •Introduction
- •1. Rectifiers
- •1.1 Employment, basic constituents
- •1.2. Technical and economic indexes of rectifier
- •1.3. Classification of rectifiers
- •1.4 Calculated basic parameters of designing
- •1.5 Some definitions
- •Thyristor as logical switch
- •1.7 A single-phase half-wave rectifier
- •1.7.1 Operation of single-phase half-wave rectifier with active load
- •For a secondary winding
- •For a primary winding
- •1.7.2. Operation of the half-wave rectifier with active - inductive load and limited inductance
- •1.7.3. Operation of the half-wave rectifier with resistive-capacitive load
- •1.8. A single-phase full-wave rectifier with a centre tap
- •1.8.1. Operation of a full-wave rectifier with a centre tap with an active load
- •1.7.2. Operation of a full-wave rectifier with centre tap and active - inductive load and limitеd inductance
- •1.8.3. Operation of a full-wave rectifier with centre tap and active - inductive load with infinite inductance
- •1.8.4. Consideration of a stage of switching of thyristors for a full-wave rectifier with centre tap and active - inductive load with infinite inductance
- •1.8.5 An external characteristic in per unit values
- •1 .9 A single-phase bridge rectifier
- •Figure 1.18
- •From cathode group thyristors current is flowing through that the right one witch have anode voltage greater than other one.
- •From anode group thyristors current is flowing through that the right one witch have cathode voltage less than other one.
- •1.10 The three-phase rectifier with a centre tap
- •1.10.3 The controlled three-phase circuit with a centre tap
- •1.10.4 The account of a stage of switching for three phase rectifier with centre tap
- •1.10.5 External characteristic
- •1.11 Three-phase bridge rectifier
- •The external characteristic
- •1.12 The double three-phase rectifier with balancing reactor
- •1.12.2. Definition of parameters for a choice of thyristors, calculation of the transformer and the balancing reactor
- •1.12.3 Merits and demerits, conditions of application
- •1.13 Equivalent polyphase circuits
- •1.13.2. Parallel connection of double three-phase bridge rectifiers
- •Average value of the rectified voltage is
- •1.14 Operation of the rectifier with opposite- emf
- •1.14.1. Operation of the half-wave rectifier with center tap with opposite- emf and active load
- •1.14.2. Operation of the half-wave rectifier with center tap and opposite-emf and active-inductive load
- •2. Dependent inverters
- •2.1 Transition from a rectifying conditions to an inverting conditions
- •External characteristics
- •3. Equipment and characteristics
- •3.1 Transformers for converting sets
- •3.2 The higher harmonics of a current and a voltage
- •The higher harmonics in a curve of the rectified voltage
- •3.2.3 The higher harmonics in a curve of a prime current
- •3.3. Power characteristics of the converter
- •3.3.1. Efficiency
- •3.3.2 Power factor
1. Rectifiers
1.1 Employment, basic constituents
The rectifier is a device for converting of an alternating current into a direct current.
The rectifiers with semiconductor-controlled rectifiers (thyristors) except for rectification can ensure regulating of the rectified voltage over a wide range.
The rectifier can be presented as the block diagram:
Fig. 1.1
1 – Power converting transformer (PT);
2 – Rectifying block (RB);
3 – Filter (F);
4 – Load (L);
5 – Control and regulating system (C and RS);
PT – serves for the coordination of input and output voltage of the rectifier. It is possible by different modes of junctions of transformer windings according to the different probable circuits of rectification. The voltage of a secondary winding of the transformer determines a value of the rectified voltage at uncontrolled state.
The transformer electrically separates supply network from network of alternating-currenta circuit of a load. Its presence is unessential – RB can be arranged directly to the network.
RB – connecting valves arrangealternating-current secondary voltage of the transformer to a circuit of a load in every given part of a period thus waveform of rectified voltage would have direct component. The correlations between voltages and currents on a side of AC network of alternating-current and on a side of a load are determined by the scheme of rectification.
F – filter ensures a required level of harmonics of rectified voltage and current. As filtering components connected in series sequentially joint chokes and in parallel capacitors are applied.
Except for the basic constituents the powerful rectifier can have special devices for compensation of reactive power.
1.2. Technical and economic indexes of rectifier
There are basic indexes defining expediency of use of the concrete circuit of rectification: cost, EFFICIENCY, mass and dimension (it depends in the main from an number and parameters of semiconductor valves and from power of a transformer equipment), harmonic structure of a waveform of rectified voltage, harmonic structure of a current of a primary winding of a transformer, power-factor.
1.3. Classification of rectifiers
According to an output power: low (units of kW), average (tens of kW) and high. Such separation carries uncertain character.
According to number of phases of a supply network: single-phase and three-phase rectifiers.
Depending on the scheme of connection semiconductor valves and connection of transformer windings: single-cycle and two-cycle.
A scheme at which the current flowing through secondary windings of transformer doesn’t vary direction names as single-cycle.
A scheme at which the current flowing through secondary windings of transformer varies direction names as two-cycle.
For the single-cycle schemes the ratio of a frequency of pulsation of the rectified voltage to a frequency of a network (a multiplicity of the pulsation) is equal to number of phases of a secondary winding of the transformer; for two-cycle schemes it is twice more.
According to regulating: regulated and unregulated.