GB/T 3859.2-1993 Guidelines for the application of semiconductor converters
Some standard content:
National Standard of the People's Republic of China
Semiconductlor convertors
Application guide
GB/T 3859.293
Substitutes GB385983
This standard equivalently adopts TE1461-2 (1991) Semiconductor converters: General requirements and grid-commutated converters Part 2: Application guide".
1 Subject content and scope of application
1.1 Subject content
This standard provides information on converter application, including calculation methods and further description of relevant performance. 1.2 Scope of application
This standard mainly involves grid-commutated converters. The contents and calculation methods described are based on grid-commutated converters. However, some chapters (such as data on equivalent junction temperature calculation and safe operation) are also applicable. This standard is an extension and supplement to GB/T3859.1. Its content mainly explains the technical conditions, performance and changes of the converter, and provides relevant background materials and calculation methods, providing a reference for the application of converters and GB/T3859.1. 2 Reference standards
GB/T3859.1: Provision of basic requirements for semiconductor power converters GB/T3859.3 Semiconductor power converters, transformers and reactors GB10236 Guidelines for mutual interference between semiconductor converters and power grids and their protection methods GB/T 2900.33 Terminology of power electronics technology GB4208 Classification of enclosure protection, etc.
3 Terms and definitions
Given here are the terms and definitions used in this standard. For other terms related to converters and power electronics technology, please refer to GB/T3859.1 and GB/T2900.33: Some terms may have broader meanings in other contexts and only reflect the specific meanings when used in this standard.
3.1 Terminology of converter faults
3.1.1 conduction through During converter operation, one arm of the thyristor connection fails to achieve forward blocking at the end of the normal conduction period, causing the thyristor to continue to flow DC current during the off-state period (see Figure 1a)). 3.1.2 Turn-on failure One arm of the converter connection fails to achieve conduction during the normal conduction period, or fails to turn on at the correct moment (see Figure 1c)). Note: Slight asymmetry caused by slight changes in the converter delay angle is not considered a turn-on failure. 3.1.3 breakthrough During the normal off-state period, one arm of the converter loses its forward blocking capability, causing a on-state current to flow during part of the period. Approved by the State Administration of Technical Supervision on December 27, 1993, and implemented on September 1, 1994
(see Figure 1b)).
GB/T 3859.293
Note that punch-through can occur during rectification operation or during inverter operation, and can be caused by various reasons, such as excessive junction temperature, voltage surge higher than the rated off-state peak value, and excessive off-state voltage rise rate or inappropriate gate current. 3.1.4 Breakdown
A fault that causes a semiconductor device to permanently lose its forward blocking or reverse blocking characteristics (forward breakdown or reverse breakdown). 3.1.5 Falsc firing
A valve or arm is opened at an incorrect time.
3.1.6 Coturnulalion failure The current fails to be transferred from the conducting arm connected to the thyristor to the successive arm. C
Figure 1 Voltage during converter fault
a) Arm 3 through, b) Arm 2 through c) Arm 2 open fault 3.2 Terms related to converter transient phenomena 3.2.1 DC side transient process DC side transient process Voltage transient process caused by the sharp change of current voltage on components such as inductors and capacitors in the DC circuit. 3.2.2 Power supply commutation transient process (repetitive transient process) Commulation transient on line (repetitive transient process) Transient change of voltage in the AC power grid after commutation. 3.3 Terms about harmonics
3. 3. 1 Harmonic
Sinusoidal components with frequencies that are integer multiples of the fundamental frequency contained in non-sinusoidal periodic waveforms. 3.3.2 Characteristic harmonics (of converters) GE/T 3859. 2—93
Those harmonics produced by converters under ideal three-phase symmetry. For converters that produce pulses, the characteristic harmonics are K·p±1, where K-1, 2, 3.....
3.3.3 Non-characteristic harmonics Harmonics other than the characteristic harmonics produced by converters 3.3.4 System disturbances Disturbances caused by a series of circumstances such as load changes in the distribution system, transient processes of switches, changes in the structure of the power supply network, etc., can generally only be determined by statistical values. Examples of such disturbances include: overvoltage, switching transients, lightning; voltage changes caused by motor starting and switching capacitors; single-phase grounding, phase-to-phase faults and fault clearing; semi-permanent voltage imbalance, which should be specified by the ratio of negative sequence to positive sequence; frequency changes and phase drift:
ripples are controlled by signals:
"harmonics of voltage and current.
3.3.5 Converter disturbances converter generated disturbances Disturbances caused by nonlinear changes in converter load. Examples of such disturbances include: voltage drops and swells, expressed as the difference from the adjacent steady-state voltage root mean square value! Harmonic currents, expressed as specified operating conditions The following values are used to represent the order, amplitude and phase relationship of the following: a) average value, i.e. the value with the highest probability of occurrence; b) maximum value, i.e. the accidental value in a short time (such as 1 minute). Commutation gap, represented by width, depth and area; repetitive transition process caused by commutation, represented by energy, peak value, rise rate, etc. like narrow pulse; non-repetitive transition process caused by factors such as closing surge current of transformer, clearing internal or external faults; a non-integer harmonic (such as frequency converter). Note: ① The above interference may be generated by the converter itself or other converters, and the actual downlink level of the studied area may change with the change of network impedance: ② When using multiple multi-pulse converters and converters with phase-shifting transformers, harmonics may It can become a secondary problem, while the voltage change becomes the key to the problem. 4 Marking of the converter
4.1 Electrical connection mark
According to the relevant standards of power electronics.
4.2 Marking of load type
In order to ensure the safe and reliable operation of the converter, the manufacturer of the converter should explain the load type and characteristics applicable to the designed converter and its rated value in the relevant technical documents of the converter (technical conditions, instructions, etc.), and remind users to ensure that the selected converter is suitable for the load used.
The load types and marking letters of the converter are as follows: a. Resistive load (W):
b. Large inductive load (I.), for example: DC motor magnetic field, electromagnet, reactor with high X/R ratio, etc., inductive loads that require voltage reverse overvoltage protection;
. Motor (M);
d. Battery charging (B);
Capacitive load (C), such as: energy storage battery, capacitor bank, electrochemical device, inverter (voltage type) and other energy storage loads: e.
Regenerative load (G), such as: hoisting, winch, electric locomotive traction and other regenerative loads that need to handle regenerative energy and protect the main circuit.
4.3 Symbols for cooling methods
4.3.1 Letter symbols used
GB/T 3859.2-93
4.3.1.1 Letter symbols for cooling medium or heat transfer medium (see Table 1). Table 1
Cooling medium or heat transfer medium
Mineral oilbZxz.net
Insulating fluid (not mineral oil)
Fluid for two-phase cooling
4.3.1.2 Letter symbols for circulation method (see Table 2). Table 2
Natural (convection)
Forced (not specially equipped with a drive device)
Forced (the evaporator has a drive device)
Evaporative cooling
4.3.2 Arrangement of letter combinations
4.3.2.1 Direct cooling
Academic symbol
Henry symbol
Direct cooling is marked with two letters, and the arrangement and combination are as follows: the letter symbol of the cooling medium is in front (left), and the letter symbol of the circulation method is in the back (right). For example:
AN: represents air cooling, natural convection. 4.3.2.2 Indirect cooling
Indirect cooling is marked with four letters, and the arrangement and combination are as follows: the first (left) two letters represent the heat transfer medium and its circulation method, and the last (right) two letters represent the cooling medium and its circulation method. For example: OFAF: represents the use of oil with forced circulation as the heat transfer medium and air with forced circulation (by fan) as the cooling medium. 4.3.2.3 Mixed cooling method
If the converter uses natural or forced circulation methods alternately during operation, two groups of letters separated by a slash are used to represent this mixed cooling method. The two groups of symbols each represent a cooling method used. Generally, the group before the slash (left) corresponds to the one with lower cooling efficiency or lower ambient temperature, while the symbol for the cooling method with higher cooling effect is placed on the side of the slash. The arrangement of the two groups of letter symbols is in accordance with the provisions of 4.3.2.1 and 4.3.2.2. Therefore, in fact, the mixed cooling method is marked by the symbols of each cooling method used plus a slash.
a For direct mixed cooling, two groups of two letters separated by a slash are used to mark. For example: AN/AF: It means mixed cooling using direct natural air cooling and direct forced air cooling. b. For indirect mixed cooling, two groups of four letters separated by a slash are used to mark. For example: OFAN/OFAF: It means that the heat transfer medium of indirect cooling is all in the forced oil circulation mode, while the cooling medium is a mixed cooling mode of alternating natural air and forced air circulation. 4.4 Marking of line ends and wire colors of converters 4.4.1 Marking of line ends
GB/T 3859.2-93
For the convenience of manufacturing, installation and use, when necessary (usually marked on the electrical schematic), the various input and output wires of the converter, the main circuit, secondary circuit and trigger circuit connections should be marked at their ends. The marking should be clear and easy to identify, and the marking symbols and marking methods should comply with the provisions of the product technical conditions.
4.4.2 Marking of wires and busbars Color
The color marking of the input and output wires of the converter should comply with the provisions of Table 3. Table 3
Wire type
Neutral line
Grounded neutral line
Marking color
Yellow and green alternately (each width 15~100mm) Brown
Note, ① Direction-variable DC busbar is based on the main working mode (first working mode). ② The arrangement position is based on the direction of the product. 5 Supplementary explanation on the technical performance of the converter 5.1 Application field of the converter
5.1.1 As an electric energy conversion device
DC load: various adjustable or non-adjustable DC power supplies, stable power supplies: AC power controller (can output AC or DC); Arrangement position
upper left, or far
in the middle
down, or right, or near
up, or left, or far
down, or there, or near
lowest, or right, or closest|| tt||AC frequency conversion: grid phase conversion, slip energy feedback, mechanical phase conversion converter, white phase conversion converter (voltage type, current type); speed regulation:
electrochemical processing (electrolysis, electroplating, electrophoresis) computer power supply:
traction substation, railway, tram, mine, electric vehicle; communication power supply:
electromagnet, magnetic field power supply,
radio transmitter DC power supply:
plasma cutting;
arc furnace DC power supply;
solar energy utilization.
improve the quality of power supply and use
high and medium voltage systems: power factor compensation in power transmission and distribution systems and factories; low voltage systems, energy-saving technology!
independent and backup power supply,
solar energy, wind energy or chemical energy DC or AC power supply. 5.2 Main technical parameters of converter
5.2.1 Items that must be specified
GB/T 3859.2-93
The contents of GB/T3859.1, especially the contents related to rated values in Article 8.1, must be specified or explained. 5.2.2 Other technical parameters
In addition to some items specified and proposed in GB/T3859.1, there are some technical parameters related to converter design, production and operation but easily overlooked. They should be specified and explained when necessary, and the manufacturer and the user should reach an agreement on this. 5.2.2.1 Parameters related to power supply
Voltage and frequency (if applicable): rated value and its variation range, requirements on unbalance, short-time power failure, etc.; #
Short-circuit capacity (or description of power supply cable, power grid and transformer): minimum value, statistical average value, maximum value; Other loads that may exist in the same power supply network: such as motors, capacitor banks, electric furnaces, etc., should be specially stated: interference limit (frequently occurring or allowed); grounding method,
Parameters related to output
Output voltage and frequency (if applicable):
Required range of output variation (continuous or graded); reverse capability of voltage and (or) current (quadrant of operation); allowable fluctuation range of voltage, current and frequency: load characteristics;
grounding method;
output waveform distortion, etc.
5.2.2.3 Description of the following environmental conditions
Temperature, tropical, cold climate:
Temperature, humidity, dust content;
Description of various abnormal working conditions;
Installation outdoors or indoors;
Protection level (according to GB4208);
Design and manufacturing basis, (standard code)
5.2.2.4 Description of the following electrical use conditions a
Power supply bus condition:
Inverter-only system (supplying power to the inverter only); general-purpose system (supplying power to AC motor loads at the same time); high-quality power supply system (supplying power to computers, medical equipment and other types of loads with low anti-interference ability); Equipment anti-interference level: all parameters can be used to select the anti-interference level. h.
5. 2. 3 About abnormal working conditions
5.2.3.1 Determination of special ambient temperature conditions If the ambient temperature of the converter does not meet the requirements of GB/T3850.1 Section 5.1: It can be handled as follows: b. Different cooling medium temperatures are specified for the converter and converter transformer; c. The supplier and the buyer negotiate and reach an agreement on the maximum and minimum ambient temperature or the temperature of the cooling medium; c. Use with reduced capacity as specified in Appendix A.
5.2.3.2 Provisions on dust and solid particle content Under normal circumstances, both the supplier and the buyer have the obligation to remind the other party to pay attention to the pollution of the ambient air in the installation and operation site of the converter when placing an order. If it exceeds the pollution level requirements of the general industrial environment, it may affect the performance and safe operation of the converter. In this case, it is necessary to take corresponding preventive measures, or design the converter suitable for special environmental conditions with severe pollution. 5.3 Calculation factors
GB/T3859.2-93
Because there are many other types of electrical connections available for converters in addition to the seven most commonly used electrical connections given in GB/T 3859.1, the calculation factors given in Table 4 are actually a supplement to GB/T3859.1. The letters and definitions used are the same as those specified in GB/T3859.1. When using letters not included in GB/T3859.1 or letters and definitions that differ from GB/T 3859.1, this standard provides explanations at appropriate locations.
5.3.1 Voltage ratio
Table 4, No. 1011, gives two voltage ratios: Ua Uu
Where: Ua——ideal no-load DC voltage; Ua—transformer valve side winding voltage;
Um—ideal no-load peak voltage between the two terminals of the arm under no-load condition, ignoring the internal and external voltage drops of the valve. The ratio remains unchanged when the load is close to the transition current. Note: For No. 5, 11 and other connection methods using phase-to-phase reactors, the ratio of Um/Ua increases when no-load. 93
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5.3.2 Transformer grid-side current factor
GB/T 3859. 2 93
The ratio of the grid-side current root mean square value I. to the DC current 1 given in column 8 of Table 4 is based on the following assumptions: that is, the DC current is smooth, the AC current is a rectangular wave, and the voltage ratio of single-beat or double-beat connection is: Ue
Grid-side line voltage
The voltage between the commutation groups on the valve side that are commutating is approximately: =rtx
For the 15th connection mode, the grid-side current factor and the delay angle have the following relationship: I'
5.3.3 Transformer valve-side current calculation factor
Column 9 of Table 1 gives the ratio of the root mean square value 1 of the valve-side current on each terminal of the transformer to the DC current. For the connection mode No. 15 below, the valve side current factor and the delay angle have the following relationship A
5.3.4 Voltage Regulation
Table 4 Column 12 gives the ratio: dx/exN, where d is the DC voltage regulation produced by the transformer commutation reactance under rated load, expressed by the standard value of U≤: e is the inductive component of the transformer impedance voltage under the rated grid-side current I of the entire equipment, expressed by the standard value of the rated AC voltage U yuan, and the transformer's commutation winding is short-circuited according to Column 17. For the connection mode with commutation number 9=3, the inductive DC voltage regulation dxv can be calculated from the commonly given rx of the three-phase transformer.
For various other connection modes, the ratio of d and depends on the ratio of the reactance on the grid side and valve side of the transformer. Note: Assume that the overlap angle is less than 2 yuan/, which is the number of pulses. In the connection mode No. 9.12.13, the data in Column 12 assume that ex is based on the line current of the entire equipment. If each converter is tested at its rated line current (0.8161a and 1.6321ax respectively), the value in column 12 is 0.5. 5.3.5 Magnetic circuit
corresponds to the connection for three-phase current supply in Table 4, assuming that the magnetic circuit is a three-column iron core. 5.3.6 Power loss factor
Column 16 gives the relationship between the power losses of the converter in normal operation and when the short-circuit test is carried out in accordance with Article 13.1415 at the rated current 11LN of the entire equipment. For the degree of accuracy of this factor, see the explanation of Article 4.1 of GB/T3859.3. 5.4 Parallel and series connection
5.4.1 Parallel or series connection of valve devices
When power semiconductor devices are connected in parallel or in series, certain measures should be taken to ensure that all devices operate within their rated voltage and current range (see GB/T, 3859.12).
If the manufacturer relies on the selection of device parameters to achieve the above purpose, it should be stated in the relevant product documents. 5.4.2 Parallel or series connection of devices and equipment units5.4.2.1 Parallel||t t||GB/T3859.293
: Without voltage regulation: When the designed equipment is connected in parallel, each parallel unit should not exceed the rated value when the total rated output is running.
If the equipment is to be operated in parallel with other power supplies with different characteristics, the requirements for load distribution should be specifically specified. b. With voltage regulation: When such equipment needs to be operated in parallel, the requirements for load distribution should be specifically specified. 5.4.2.2 Series connection
When the converter is connected in parallel When the devices or converter units are operated in series, protective measures must be taken to ensure that each unit can operate within the rated voltage limit when the AC side is open and the DC side is connected to an active load. When operating in series, the voltage to ground may be much higher than the voltage between the two terminals of each device or equipment. In this case, the insulation design and test of the converter should be based on this higher voltage to ground. 5.5 Power Factor
5.5.1 Overview
For converters with 6 or more pulses, the total power The meaning of the factor is not clear, and the displacement factor cos of the fundamental wave is usually practical.
The displacement factor cos is related to the grid-side parameters of the converter transformer. For this reason, if a guarantee is required, unless otherwise agreed, the calculation of the displacement factor can be assumed to be symmetrical and the voltage is a sine wave. For the displacement factor of three-phase thyristors connected in a uniform manner, it should be calculated and determined in accordance with Article 5.5.4. For single-phase equipment with a rated output greater than 300kW, three-phase non-uniformly connected equipment, and sequentially controlled converters, the displacement factor should be specified. Method for determining the displacement factor.
When the converter operates in rectification mode, it consumes active and reactive power from the grid system. When the converter operates in inversion mode, it delivers active power to the grid, but still consumes reactive power from the grid. Note: In many applications, such as small pulse width modulation (PWM) drives, when there are only small or no reactors, the ripple has a significant impact on the overall power factor. 5.5.2 Symbol used in determining the displacement factor cosy: When the delay angle is zero, the rated DC current is Displacement factor; COsaN: displacement factor at rated DC current when the delay angle is ; dn: resistive DC voltage regulation at rated load, expressed in unit value of Ua. &n-de+dby;d: inductive DC voltage regulation at rated load, expressed in unit value of Ua. ddxn+dydb,dxby: resistive and inductive DC voltage regulation generated by other parts of the converter such as cathode reactor, grid-side reactor and transformer (if any) at rated DC current, expressed in unit value of Ua The value is expressed as; dnNdtN is the resistive and inductive DC voltage regulation rate caused by the converter transformer at rated DC current, expressed in unit value; d: At rated DC current, when the voltage RMS value between the grid-side terminals remains constant: the additional DC voltage regulation rate caused by the output AC system impedance, expressed in unit value of U:; EaN: the back EMF of the DC motor at rated speed and rated magnetic flux; p: the number of pulses;
PiN is the grid-side active power at rated load, PLy-Ua·IaN+P' iNPIN: power loss of circuit resistance at rated load; Q1LN: reactive power of grid-side fundamental current I11N at rated load, Fis: rated frequency of grid;
IdN: rated DC current;
R: motor armature circuit resistance;
R: impedance of power supply system,
Re: short-circuit ratio;
SiN: apparent power of grid-side fundamental current IiLN at rated load. SIN=U·Ia=UiN·IuN·31. 5.4 Parallel and series connection
5.4.1 Parallel or series connection of valve devices
When power semiconductor devices are connected in parallel or in series, certain measures should be taken to ensure that all devices operate within their rated voltage and current range (see GB/T, 3859.12).
If the manufacturer relies on the selection of device parameters to achieve the above purpose, it should be stated in the relevant product documents. 5.4.2 Parallel or series connection of devices and equipment units 5.4.2.1 Parallel||t t||GB/T3859.293
: Without voltage regulation: When the designed equipment is connected in parallel, each parallel unit should not exceed the rated value when the total rated output is running.
If the equipment is to be operated in parallel with other power supplies with different characteristics, the requirements for load distribution should be specifically specified. b. With voltage regulation: When such equipment needs to be operated in parallel, the requirements for load distribution should be specifically specified. 5.4.2.2 Series connection
When the converter is connected in parallel When the devices or converter units are operated in series, protective measures must be taken to ensure that each unit can operate within the rated voltage limit when the AC side is open and the DC side is connected to an active load. When operating in series, the voltage to ground may be much higher than the voltage between the two terminals of each device or equipment. In this case, the insulation design and test of the converter should be based on this higher voltage to ground. 5.5 Power Factor
5.5.1 Overview
For converters with 6 or more pulses, the total power The meaning of the factor is not clear, and the displacement factor cos of the fundamental wave is usually practical.
The displacement factor cos is related to the grid-side parameters of the converter transformer. For this reason, if a guarantee is required, unless otherwise agreed, the calculation of the displacement factor can be assumed to be symmetrical and the voltage is a sine wave. For the displacement factor of three-phase thyristors connected in a uniform manner, it should be calculated and determined in accordance with Article 5.5.4. For single-phase equipment with a rated output greater than 300kW, three-phase non-uniformly connected equipment, and sequentially controlled converters, the displacement factor should be specified. Method for determining the displacement factor.
When the converter operates in rectification mode, it consumes active and reactive power from the grid system. When the converter operates in inversion mode, it delivers active power to the grid, but still consumes reactive power from the grid. Note: In many applications, such as small pulse width modulation (PWM) drives, when there are only small or no reactors, the ripple has a significant impact on the overall power factor. 5.5.2 Symbol used in determining the displacement factor cosy: When the delay angle is zero, the rated DC current is Displacement factor; COsaN: displacement factor at rated DC current when the delay angle is ; dn: resistive DC voltage regulation at rated load, expressed in unit value of Ua. &n-de+dby;d: inductive DC voltage regulation at rated load, expressed in unit value of Ua. ddxn+dydb,dxby: resistive and inductive DC voltage regulation generated by other parts of the converter such as cathode reactor, grid-side reactor and transformer (if any) at rated DC current, expressed in unit value of Ua The value is expressed as; dnNdtN is the resistive and inductive DC voltage regulation rate caused by the converter transformer at rated DC current, expressed in unit value; d: At rated DC current, when the voltage RMS value between the grid-side terminals remains constant: the additional DC voltage regulation rate caused by the output AC system impedance, expressed in unit value of U:; EaN: the back EMF of the DC motor at rated speed and rated magnetic flux; p: the number of pulses;
PiN is the grid-side active power at rated load, PLy-Ua·IaN+P' iNPIN: power loss of circuit resistance at rated load; Q1LN: reactive power of grid-side fundamental current I11N at rated load, Fis: rated frequency of grid;
IdN: rated DC current;
R: motor armature circuit resistance;
R: impedance of power supply system,
Re: short-circuit ratio;
SiN: apparent power of grid-side fundamental current IiLN at rated load. SIN=U·Ia=UiN·IuN·31. 5.4 Parallel and series connection
5.4.1 Parallel or series connection of valve devices
When power semiconductor devices are connected in parallel or in series, certain measures should be taken to ensure that all devices operate within their rated voltage and current range (see GB/T, 3859.12).
If the manufacturer relies on the selection of device parameters to achieve the above purpose, it should be stated in the relevant product documents. 5.4.2 Parallel or series connection of devices and equipment units 5.4.2.1 Parallel||t t||GB/T3859.293
: Without voltage regulation: When the designed equipment is connected in parallel, each parallel unit should not exceed the rated value when the total rated output is running.
If the equipment is to be operated in parallel with other power supplies with different characteristics, the requirements for load distribution should be specifically specified. b. With voltage regulation: When such equipment needs to be operated in parallel, the requirements for load distribution should be specifically specified. 5.4.2.2 Series connection
When the converter is connected in parallel When the devices or converter units are operated in series, protective measures must be taken to ensure that each unit can operate within the rated voltage limit when the AC side is open and the DC side is connected to an active load. When operating in series, the voltage to ground may be much higher than the voltage between the two terminals of each device or equipment. In this case, the insulation design and test of the converter should be based on this higher voltage to ground. 5.5 Power Factor
5.5.1 Overview
For converters with 6 or more pulses, the total power The meaning of the factor is not clear, and the displacement factor cos of the fundamental wave is usually practical.
The displacement factor cos is related to the grid-side parameters of the converter transformer. For this reason, if a guarantee is required, unless otherwise agreed, the calculation of the displacement factor can be assumed to be symmetrical and the voltage is a sine wave. For the displacement factor of three-phase thyristors connected in a uniform manner, it should be calculated and determined in accordance with Article 5.5.4. For single-phase equipment with a rated output greater than 300kW, three-phase non-uniformly connected equipment, and sequentially controlled converters, the displacement factor should be specified. Method for determining the displacement factor.
When the converter operates in rectification mode, it consumes active and reactive power from the grid system. When the converter operates in inversion mode, it delivers active power to the grid, but still consumes reactive power from the grid. Note: In many applications, such as small pulse width modulation (PWM) drives, when there are only small or no reactors, the ripple has a significant impact on the overall power factor. 5.5.2 Symbol used in determining the displacement factor cosy: When the delay angle is zero, the rated DC current is Displacement factor; COsaN: displacement factor at rated DC current when the delay angle is ; dn: resistive DC voltage regulation at rated load, expressed in unit value of Ua. &n-de+dby;d: inductive DC voltage regulation at rated load, expressed in unit value of Ua. ddxn+dydb,dxby: resistive and inductive DC voltage regulation generated by other parts of the converter such as cathode reactor, grid-side reactor and transformer (if any) at rated DC current, expressed in unit value of Ua The value is expressed as; dnNdtN is the resistive and inductive DC voltage regulation rate caused by the converter transformer at rated DC current, expressed in unit value; d: At rated DC current, when the voltage RMS value between the grid-side terminals remains constant: the additional DC voltage regulation rate caused by the output AC system impedance, expressed in unit value of U:; EaN: the back EMF of the DC motor at rated speed and rated magnetic flux; p: the number of pulses;
PiN is the grid-side active power at rated load, PLy-Ua·IaN+P' iNPIN: power loss of circuit resistance at rated load; Q1LN: reactive power of grid-side fundamental current I11N at rated load, Fis: rated frequency of grid;
IdN: rated DC current;
R: motor armature circuit resistance;
R: impedance of power supply system,
Re: short-circuit ratio;
SiN: apparent power of grid-side fundamental current IiLN at rated load. SIN=U·Ia=UiN·IuN·3
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