# Glossary of power electronics

This glossary of power electronics is a list of definitions of terms and concepts related to power electronics in general and power electronic capacitors in particular. For more definitions in electric engineering, see Glossary of electrical and electronics engineering. For terms related to engineering in general, see Glossary of engineering.
The glossary terms fit in the following categories in power electronics:
* Electronic power converters; converters, rectifiers, inverters, filters.
* Electronic power switches and electronic AC power converters; switches and controllers.
* Essential components of electric power equipment; device, stack, assembly, reactor, capacitor, transformer, AC filter, DC filter, snubber circuit.
* Circuits and circuit elements of power electronic equipment; arms and connections.
* Operations within power electronic equipment; commutations, quenchings, controls, angles, factors, states, directions, intervals, periods, frequencies, voltages, breakthroughs and failures, breakdowns, blocking and flows.
* Properties of power electronic equipment
* Characteristic curves of power electronic equipment
* Power supplies
* A
* B
* C
* D
* E
* F
* G
* H
* I
* J
* K
* L
* M
* N
* O
* P
* Q
* R
* S
* T
* U
* V
* W
* X
* Y
* Z
* See also
* References
* Notes
* External links

## A
### AC capacitor

    A capacitor essentially designed for operation with alternating voltage.

### AC conversion factor

    For AC conversion, the ratio of the fundamental output power to the fundamental input power.

### AC converter

    A converter for AC conversion.

### AC filter

    A filter on the AC side of a converter, designed to reduce the circulation of harmonic currents in the associated system.

### AC voltage converter

    An AC converter for changing the voltage.

### (electronic) AC (power) conversion

    Electronic conversion from AC to AC

### (electronic) AC/DC (power) conversion

    Electronic conversion from AC to DC or vice versa.

### AC/DC converter

    An electronic converter for rectification or inversion or both.

### angle of overlap

    The commutation interval expressed in angular measure.

### (valve) arm

    A part of the circuit of a power converter or switch bounded by any two AC or DC terminals and including one or more simultaneously conducting electronic valve devices connected together and other components if any.

### asymmetrical phase control

    Phase control with different delay angles in the principal arms of a converter connection or commutating group.

### automatic switching on

    The property of an equipment having a forced characteristic such that the equipment is switched on automatically.

### automatic switching off

    The property of an equipment having a forced characteristic such that the equipment is switched off automatically.

### auto-sequential commutation

    A method of capacitor commutation where the next principal arm to conduct in sequence when turned on connects the capacitor supplying the commutating voltage to the foregoing principal arm.

### auxiliary arm

    Any valve arm other than a principal arm.

## B
### basic converter connection

    The electrical arrangement of principal arms in a converter.

### step-up converter

    A direct DC converter providing an output voltage which is higher than the input voltage.

### boost and buck connection

    A series connection of two or more converter connections the direct voltages of which may be added or subtracted depending on the control of the individual connections.

### breakdown (of an electronic valve device or of a valve arm)

    A failure that permanently deprives an electronic valve device or a valve arm of its property to block voltage.

### breakthrough

    A failure by which a controllable valve device or an arm consisting of such devices loses its ability to block voltage during the forward blocking interval.

### bridge connection

    A double-way connection of pairs of arms such that the center terminals are the phase terminals of the AC circuit, and that the outer terminals of like polarity are connected together and are the DC terminals.

### step-down converter

    A direct DC converter providing an output voltage which is lower than the input voltage.

### by-pass arm

    An auxiliary arm providing a conductive path which allows the current to circulate without an interchange of power between source and load.

## C
### capacitor commutation

    A method of self-commutation in which the commutating voltage is supplied by capacitors included in the commutation circuit.

### capacitor element (or element)

    An indivisible part of a capacitor consisting of two electrodes separated by a dielectric.

### capacitor losses

    The active power consumed by a capacitor.

### capacitor unit (or unit)

    An assembly of one or more capacitor elements in the same container with terminals brought out.

### capacitor bank

    An assembly of two or more capacitor units, electrically connected to each other.

### capacitor

    A general term used when it is not necessary to state whether reference is made to an element, a unit or a capacitor bank.

### capacitor equipment

    An assembly of capacitor units and their accessories intended for connection to a network.

### circuit angle

    In a rectifier connection, the phase angle between the peak of the line to neutral voltage on the AC line side and the simultaneous or next peak of the unsmoothed direct voltage at zero current delay angle.

### circuit crest working off-state voltage

    The highest instantaneous value of the off-state voltage developed across a controllable valve device or an arm consisting of such devices, excluding all repetitive and non-repetitive transients.

### circuit crest working reverse voltage

    The highest instantaneous value of the reverse voltage developed across a reverse blocking valve device or an arm consisting of such devices, excluding all repetitive and non-repetitive transient voltages.

### circuit non-repetitive peak off-state voltage

    The highest instantaneous value of any non-repetitive transient off-state voltage developed across a controllable valve device or an arm consisting of such devices.

### circuit non-repetitive peak reverse voltage

    The highest instantaneous value of any non-repetitive transient reverse voltage developed across a reverse blocking valve device or an arm consisting of such devices.

### circuit repetitive peak off-state voltage

    The highest instantaneous value of the off-state voltage developed across a controllable valve device or an arm consisting of such devices, including all repetitive transient voltages but excluding all non-repetitive transient voltages.

### circuit repetitive peak reverse voltage

    The highest instantaneous value of a reverse voltage developed across a reverse blocking valve device or an arm consisting of such devices, including all repetitive transient voltages but excluding all non-repetitive transient voltages.

### circuit reverse blocking interval

    The interval during which a reverse blocking valve device or an arm consisting of such devices is in the reverse blocking state.

### circuit off-state interval

    The interval during which a controllable valve device or an arm consisting of such devices is in the off state.

### characteristic (curve) (of a converter)

    A curve showing the relationship between the values of the output voltage and the values of the output current.

### commutating voltage

    The voltage which causes the current to commutate.

### commutation

    In a power converter the transfer of current from one conducting arm to the next to conduct in sequence, without interruption of the current, both arms conducting simultaneously during a finite time interval.

### commutation circuit

    The circuit consisting of the commutating arms and the source providing the commutating voltage.

### commutating group

    A group of principal arms which commutate cyclically among themselves without intermediate commutation of the current to other principal arms.

### commutation capacitor

    A capacitor included in the commutation circuit to supply commutating voltage.

### commutation inductance

    The resulting inductance in the commutation circuit.

### commutation interval

    The time interval in which commutating arms are carrying principal current simultaneously.

### commutation failure

    A failure to commutate the current from a conducting arm to the succeeding arm.

### commutation notch

    A periodic voltage transient that may appear in the AC side voltage of a line or machine commutated converter due to the commutation.

### commutation number

    The number of commutations from one principal arm to another during one elementary period in each commutating group.

### commutation reactor

    A reactor included in the commutation circuit to increase the commutation inductance.

### composite characteristic

    A characteristic consisting of parts of the stabilized voltage and stabilized current characteristics.

### conducting direction (of an electronic valve device or of a valve arm)

    The direction in which an electronic valve device or a valve arm is capable of conducting current.

### conduction interval (of a valve arm)

    That part of an elementary period in which the valve arm conducts.

### conduction ratio

    The ratio of the conduction interval to the sum of the conduction interval and the idle interval.

### conduction through

    In inverter operation, the situation that a valve arm continues conduction at the end of the normal conduction interval or at the end of the hold-off interval.

### (electronic) (power) conversion

    Change of one or more of the characteristics of an electric power system essentially without appreciable loss of power by means of electronic valve devices.

### (electronic) (power) converter

    An operative unit for electronic power conversion, comprising one or more electronic valve devices, transformers and filters if necessary and auxiliaries if any.

### converter connection

    The electrical arrangement of valve arms and other components essential for the function of the main power circuit of a converter.

### converter section of a double converter

    That part of a double converter in which the main direct current when viewed from the DC terminals always flows in the same direction.

### controllable valve device

    A valve device the current path of which is bistably controlled in its conducting direction.

### constant current power supply

    A power supply that stabilizes output current with respect to changes of influence quantities.

### constant voltage power supply

    A power supply that stabilizes output voltage with respect to changes of influence quantities.

### constant voltage or constant current power supply

    A stabilized power supply that operates as a constant voltage power supply or constant current power supply depending on load conditions.

### constant voltage to constant current crossover

    The behavior of a stabilized power supply that automatically converts the mode of operation from voltage stabilization to current stabilization when the output current reaches a preset value, and vice versa.

### continuous flow (of direct current)

    A flow of direct current which is not periodically interrupted.

### conversion factor (in general)

    The ratio of the fundamental output power or DC output power to the fundamental input power or DC input power.

### container temperature rise (△θcase) (capacitor)

    The difference between the temperature of the hottest point of the container and the temperature of the cooling air.

### controlled ideal no-load direct voltage

    The theoretical no-load direct voltage of an AC/DC converter corresponding to a specified trigger delay angle assuming no threshold voltages of electronic valve devices and no voltage rise at small loads.

### controlled conventional no-load direct voltage

    The mean value of the direct voltage corresponding to a specified trigger delay angle which would be obtained by extrapolating the direct voltage/current characteristic from the region of continuous flow of direct current to zero current.

### conventional no-load direct voltage

    The mean value of the direct voltage which would be obtained by extrapolating the direct voltage/current characteristic. from the region of continuous flow of direct current to zero current at zero trigger delay angle, i.e. without phase control.

### cooling-air temperature (θamb) (capacitor)

    The temperature of the cooling air measured at the hottest position in the bank, under steady-state conditions, midway between two units. If only one unit is involved, it is the temperature measured at a point approximately 0-1 m away from the capacitor container and at two-thirds of the height from its base.

### crossover area

    With stabilized power supplies, the range of values of the output quantities within which a change of mode of operation occurs, e.g. from constant voltage to constant current.

### crossover point

    With stabilized power supplies a point given by the intersection of the lines representing the nominal values of the two stabilized output quantities, usually the centre of the crossover area.

### current delay angle

    The time expressed in angular measure by which the starting instant of current conduction is delayed by phase control.

### current pulse width (τ) (capacitor)

    The time of current flow during the charging or discharging from one voltage value to another of the capacitor.

### current fed inverter

    A current stiff inverter.

### current stiff AC/DC converter

    An electronic AC/DC converter having an essentially smooth current on the DC side provided e.g. by means to reduce the harmonic currents.

### cycloconverter

    A direct frequency converter.

## D
### DC capacitor

    A capacitor essentially designed for operation with direct voltage.

### DC converter

    A converter for DC conversion.

### DC conversion factor

    for DC conversion, the ratio of the DC power value on the load side to that on the source side.

### (electronic) DC (power) conversion

    Electronic conversion from DC to DC

### DC filter

    A filter on the DC side of a converter, designed to reduce the ripple in the associated system.

### DC form factor

    The ratio of the rms value to the mean value averaged over a full period of a periodically varying quantity having a non zero DC component.

### DC power

    The product of the direct voltage and the direct current (mean values).

### DC ripple factor

    The ratio of half the difference between the maximum and minimum value of a pulsating direct current to the mean, value of this current.

### direct AC/DC converter

    An electronic AC/DC converter without a DC or AC link.

### direct AC converter

    An AC converter without a DC link.

### direct (power) conversion

    Electronic conversion without a DC or AC link.

### DC chopper

    A DC converter without an AC link.

### direct commutation

    A commutation between two principal arms without transfer through any auxiliary arms.

### direct inverter

    An inverter without a DC link.

### direct rectifier

    A rectifier without a DC or AC link.

### direct voltage regulation

    The difference between the conventional no-load direct voltage and the direct voltage at load at the same trigger delay angle excluding the correcting effect of stabilizing means if any.

### double converter

    A current stiff reversible AC/DC converter with direct current in both directions.

### double-way connection (of a converter)

    A converter connection such that the current through each of the phase terminals of the AC circuit is bidirectional.

### duty cycle (capacitor)

    1. continuous duty; Operation time such that a capacitor is at thermal equilibrium for most of the time.
    2. intermittent duty ; Discontinuous working or operation with variable loads which should be described in terms of ON/OFF or HIGH/LOW periods with their durations.

## E
### electronic AC (power) switch

    An electronic power switch capable of switching alternating current.

### electronic AC power controller

    A unit which is able to operate as a controllable direct AC voltage converter as well as an electronic AC switch.

### electronic DC (power) switch

    An electronic power switch capable of switching direct current.

### electronic device

    A device the function of which is based on charge carriers moving through a semiconductor, a high vacuum or a gas discharge.

### elementary frequency

    The reciprocal of the elementary period.

### elementary period

    The duration of one cycle of the phenomena that are periodically repeated.

### active power filter

    A converter for filtering.

### electronic (power) switching

    Switching an electric power circuit by means of electronic valve devices.

### electronic (power) switch

    An operative unit for electronic power switching comprising at least one controllable valve device.

### electronic valve device

    An indivisible electronic device for electronic power conversion or electronic power switching, comprising a single non-controllable or bistably controlled unidirectionally conducting current path.

### equivalent series resistance of a capacitor

    An effective resistance which, if connected in series with an ideal capacitor of capacitance value equal to that of the capacitor in question, would have a power loss equal to the active power dissipated in that capacitor underspecified operating conditions.

### external commutation

    A commutation where the commutating voltage is supplied by a source outside the converter or electronic switch.

### external quenching

    A method of quenching in which the quenching results from causes external to the electronic valve device.

## F
### false firing

    The firing of a latching valve device or an arm consisting of such devices at an incorrect instant.

### flyback converter

    A DC converter where the energy is transferred from the source side to the load side during the idle interval(s) of the controllable principal arm(s) after being stored in an inductance.

### firing

    The establishment of current in the conducting direction in a latching valve device or an arm consisting of such devices.

### firing failure

    A failure to achieve conduction in a latching valve device or an arm consisting of such devices during the conduction interval.

### forward breakdown

    A failure that permanently deprives a controllable valve device or an arm consisting of such devices of its property to block forward voltage.

### forward converter

    A DC converter where the energy is transferred from the source side to the load side during the conduction interval(s) of the controllable principal arm(s).

### four-quadrant converter

    An AC/DC or DC converter with two directions of DC power flow, associated with two directions of direct voltage and two directions of direct current.

### free-wheeling arm

    A by-pass arm containing only non-controllable valve devices.

### frequency converter

    An AC converter for changing the frequency.

### forced characteristic (of a line commutated converter)

    A characteristic obtained by additional means, e.g. stabilization, with specified variation limits of influence quantities.

### fully controllable connection

    A uniform connection with all principal arms controllable.

### fundamental factor

    The ratio of the rms value of the fundamental component to the rms value of the alternating quantity.

### fundamental power

    The active power determined by the fundamental components of voltage and current.

## H
### half-controllable connection

    A non-uniform connection with half the number of principal arms controllable.

### harmonic content

    The quantity obtained by subtracting from an alternating quantity its fundamental component.

### (total) harmonic factor

    The ratio of the rms value of the harmonic content of an alternating quantity to the r.m.s. value of the quantity.

### high vacuum valve device

    An electronic valve device in which the degree of vacuum is so high that the effects of ionization are negligible.

### hold-off interval

    The interval between the instant when the on-state current of a latching valve device has decreased to zero and the instant when the same valve device is subjected to reapplied off-state voltage.

## I
### indirect AC converter

    An AC converter with a DC link.

### indirect AC/DC converter

    An electronic AC/DC converter with a DC or AC link.

### indirect commutation

    A series of commutations from one principal arm to another or back to the original one by successive commutations via one or more auxiliary arms.

### indirect (power) conversion

    Electronic conversion with one or more DC or AC link(s).

### indirect current link AC converter

    An AC converter with a current stiff DC link .

### indirect DC converter

    A DC converter with an AC link.

### indirect inverter

    An inverter with a DC link.

### indirect rectifier

    A rectifier with a DC or AC link.

### indirect voltage link AC converter

    An AC converter with a voltage stiff DC link.

### inductive direct voltage regulation

    The direct voltage regulation due to the commutation inductance(s).

### influence quantity

    In the field of power electronics any quantity generally external to a power supply which may affect its performance.

### inherent delay angle

    The current delay angle occurring, even without phase control, caused by multiple overlap.

### inherent direct voltage regulation

    The direct voltage regulation excluding the effect of the AC system impedance.

### intermittent flow (of direct current)

    A flow of direct current which is periodically interrupted.

### internal discharge device

    A device incorporated in the capacitor connecting the terminals of the unit, capable of reducing the residual voltage effectively to zero after the capacitor has been disconnected from the supply.

### internal (element) fuse

    A device incorporated in the capacitor which disconnects an element or a group of elements in the event of breakdown.

### insulation voltage (Ui)

    The RMS rated value of the insulation voltage of capacitive elements and terminals to case or earth. If not specified, the RMS value of the insulating voltage is equivalent to the rated voltage divided by a square root of 2.

### interphase transformer

    An electromagnetic device enabling the operation in parallel of two or more phase displaced commutating groups through inductive coupling between the windings placed, on the same core.

### inversion factor

    For inversion, the ratio of the fundamental output power to the DC power.

### ideal no-load direct voltage

    The theoretical no-load direct voltage of an AC/DC converter assuming no reduction by phase control, no threshold voltages of electronic valve devices, and no voltage rise at small loads.

### idle interval (of a valve arm)

    That part of an elementary period in which the valve arm does not conduct.

### filled valve device

    An electronic valve device in which the effects of the ionization of a gas play an important role.

### (electronic) (power) inversion

    Electronic conversion from DC to AC

### inverter

    AC/DC converter for inversion.

## J
### jumping characteristic

    The property of an equipment to jump from one characteristic to another, e.g. by changing the predetermined value of a stabilizing device.

## L
### latching valve device

    A controllable valve device which latches when it is turned on, that means it remains in the on state when the trigger signal has ended.

### line commutation

    An external commutation where the commutating voltage is supplied by the line.

### load commutation

    An external commutation where the commutating voltage is taken from a load other than the line.

### lowest operating temperature (θmin) (capacitor)

    The lowest temperature at which the capacitormay be energized.

## M
### machine commutation

    External commutation where the commutating voltage is supplied by a rotating machine.

### maximum current (Imax) (capacitor)

    The maximum RMS current for continuous operation.

### maximum loss power (Pmax) (capacitor)

    The maximum loss power with which the capacitor may be loaded at the maximum case temperature.

### maximum operating temperature (θmax) (capacitor)

    The highest temperature of the case at which capacitor may be operated.

### maximum peak current (i) (capacitor)

    The maximum current amplitude which occurs instantaneously during continuous operation.

### maximum surge current (is) (capacitor)

    The admissible peak current induced by a switching or any other disturbance of the system which is allowed for a limited number of times.

### metal-foil capacitor (non self-healing)

    A capacitor in which the electrodes usually consist of metal foils separated by a dielectric, in the event of breakdown of the dielectric, the capacitor does not restore itself.

### model capacitor

    A smaller unit which simulates a complete unit or element in an electrical test, without reducing the severity of the electrical, thermal or mechanical conditions.

### multi-connected converter

    A converter consisting of two or more converter units parallel connected or series connected or both, each of which is an operative converter of its own.

### multiple connection (of commutating groups)

    A connection in which two or more identical commutating groups which do not commutate simultaneously are connected in such a way that their direct currents add.

### multicycle control

    The process of varying the ratio of the number of cycles which include current conduction to the number of cycles in which no current conduction occurs.

### multicycle control factor

    The ratio between the number of conducting cycles and the sum of conducting and non-conducting cycles in the case of multicycle control.

## N
### natural characteristic (of a line commutated converter)

    A characteristic determined only by the basic parts of the equipment, e.g. transformer and valve device assembly.

### non-conducting direction (of an electronic valve device or of a valve arm)

    The reverse of the conducting direction.

### non-controllable connection

    A uniform connection with all principal arms non-controllable.

### rectifier diode

    A reverse blocking valve device the current path of which conducts in its conducting direction without any control signal being applied.

### non-recurrent surge voltage (Us) (capacitor)

    A peak voltage induced by a switching or any other disturbance of the system which is allowed for a limited number of times and for durations shorter than the basic period.

### non-reverse blocking valve device

    A controllable valve device which is not capable of blocking any voltage of more than several volts in its non-conducting direction.

### non-uniform connection

    A connection with both controllable and non-controllable principal arms.

## O
### forward blocking state

    The non-conducting state of a controllable valve device or an arm consisting of such devices when load current in the conducting direction is not allowed to flow due to the absence of a turn-on signal.

### conducting state

    The condition when conducting current flows through an electronic valve device or an arm.

### one-quadrant converter

    An AC/DC or DC converter with one possible direction of DC power flow.

### operating temperature (capacitor)

    The temperature of the hottest point on the case of the capacitor in thermal equilibrium.

### overpressure disconnector

    A disconnecting device designed to interrupt the current path in the case of abnormal increase of the internal pressure.

## P
### pair of antiparallel arms

    Two valve arms in parallel with opposite conducting directions.

### pair of arms

    Two series connected valve arms with the same conducting direction.

### parallel operation

    A mode of operation of stabilized power supplies in which all similar output terminals are connected together and arranged so that the total load is shared by all the supplies.

### phase control factor

    In the case of phase control, the ratio of the voltage at prevailing current delay angle to the voltage at zero current delay angle, all voltage drops being assumed to be zero.

### phase converter

    An AC converter for changing the number of phases.

### phase control

    The process of varying the instant within the cycle at which current conduction in an electronic valve device or a valve arm begins.

### power electronic capacitor

    A power capacitor intended to be used in power electronic equipment and capable of operating continuously under non-sinusoidal current or voltage.

### power electronics

    The field of electronics which deals with the conversion or switching of electric power with or without control of that power.

### principal arm

    A valve arm involved in the major transfer of power from one side of the converter or electronic switch to the other.

### pulse control

    The process of varying the starting or termination instants or both of a repeated current conduction in a principal arm.

### pulse control factor

    The conduction ratio of a principal arm in the case of pulse duration control, assuming the commutation inductance to be zero.

### pulse frequency (fp) (capacitor)

    The repetition rate of periodic current pulses.

### pulse frequency control

    Pulse control at variable frequency and fixed pulse duration.

### pulse frequency control

    Pulse control at variable frequency and fixed pulse duration.

### pulse number

    The number of non-simultaneous symmetrical direct or indirect commutations from one principal arm to another which occur during one elementary period.

### PWM control (abbreviation)

    Pulse control in which the pulse width or frequency or both are modulated within each fundamental period to produce a certain output waveform.

## Q
### quenching

    The termination of current flow in an arm without commutation.

### quenching voltage

    The voltage which causes quenching of the current.

## R
### reactive power converter

    A converter for reactive power compensation that generates or consumes reactive power without the flow of active power except for the power losses in the converter.

### rated AC voltage (Un) (capacitor)

    The maximum operating peak recurrent voltage of either polarity of a reversing type waveform for which the capacitor has been designed.

### rated DC voltage (Un) (capacitor)

    The maximum operating peak voltage of either polarity but of a non-reversing type wave form, for which the capacitor has been designed, for continuous operation.

### real no-load direct voltage

    The actual mean direct voltage at zero direct current.

### (electronic) (power) rectification

    Electronic conversion from AC to DC

### rectification factor

    For rectification, the ratio of the DC power to the fundamental input power.

### rectifier

    An AC/DC converter for rectification.

### regenerative arm

    A valve arm which transfers a part of the power from the load side to the source side.

### (electronic) (power) resistance control

    Control using the continuous variation of the resistance of electronic devices.

### resistive direct voltage regulation

    The direct voltage regulation due to resistance (threshold voltages of electronic valve devices excluded).

### resonant converter

    A converter using (a) resonant circuit(s) to provide commutation or to reduce switching losses [de].

### resonant frequency (fr) (capacitor)

    The lowest frequency at which the impedance of the capacitor becomes minimum.

### reversible converter

    A converter in which the direction of the power flow is reversible.

### reverse blocking state

    the non-conducting state of a reverse blocking valve device or an arm consisting of such devices when reverse voltage is applied between its main terminals (electrodes).

### reverse blocking valve device

    A valve device which is capable of blocking a specified direct voltage applied in its non-conducting direction.

### reverse breakdown

    A failure that permanently deprives a reverse blocking valve device or an arm consisting of such devices of its property to block reverse voltage.

### ripple voltage (on the DC side)

    The peak-to-peak alternating voltage component of the voltage on the DC side of a converter.

## S
### slave operation

    A mode of operation of stabilized power supplies achieving coordinated control of interconnected stabilized supplies by setting the master supply alone.

### self-commutation

    A commutation where the commutating voltage is supplied by components within the converter or the electronic switch.

### self-healing metallized dielectric capacitor

    A capacitor, the electrodes of which are deposited on the dielectric (usually by evaporation); in the event of breakdown of the dielectric, the capacitor restores itself.

### semiconductor converter

    An power converter with semiconductor valve devices.

### semiconductor switch

    An electronic power switch with semiconductor valve devices.

### semiconductor valve device

    An electronic valve device which is a semiconductor device.

### sequential phase control

    Asymmetrical phase control such that the delay angles are determined according to a given sequence.

### single converter

    A current stiff reversible AC/DC converter with direct current in one direction.

### single-way connection (of a converter)

    A converter connection such that the current through each of the phase terminals of the AC circuit is unidirectional.

### snubber (circuit)

    A subcircuit connected to one or more electronic valve devices in order to relieve it (them) of stress as for instance overvoltage transients, switching losses, high rate of rise of current or voltage, etc.

### stabilized current characteristic

    A characteristic with a stabilized output current.

### stabilized output characteristic

    A forced characteristic with an output quantity which is stabilized with respect to changes of influence quantities.

### stabilized voltage characteristic

    A characteristic with a stabilized output voltage.

### stabilization

    In the field of power electronics the reduction of the effect of changes of influence quantities on the output quantity.

### stabilized power supply

    In the field of power electronics an equipment which takes electrical energy from a source and supplies it stabilized by means inside the equipment to one or more pairs of output terminals.

### stage (of a series connection)

    A part of a series connection of two or more converter connections consisting of one or more parallel connected converter connections.

### steady-state condition (capacitor)

    Thermal equilibrium attained by the capacitor at constant output and at constant cooling-air temperature.

### symmetrical phase control

    Phase control with equal delay angles in all principal arms of a fully controllable converter connection or commutating group.

### switched valve device

    A controllable valve device which may be turned on and off by a control signal.

## T
### tangent of the loss angle (tanδ) of a capacitor

    The ratio between the equivalent series resistance and the capacitive reactance of a capacitor at specified sinusoidal alternating voltage and frequency.

### threshold voltage (of an electronic valve device)

    The value of the voltage obtained at the intersection of the voltage axis and the straight line approximation of the on-state characteristic of an electronic valve device.

### transfer factor (of a DC converter)

    The ratio of the voltage on the load side and the voltage on the source side.

### transition current

    The mean direct current of a converter connection when the direct current(s) of the commutation group(s) become(s) intermittent when decreasing the current.

### trigger advance angle

    The time expressed in angular measure by which the trigger pulse is advanced with respect to the reference instant.

### trigger delay angle

    The time expressed in angular measure by which the trigger pulse is delayed with respect to the reference instant in the case of phase control.

### triggering

    The control action to achieve firing of a latching valve device or an arm consisting of such devices.

### tolerance band

    With stabilized power supplies the range of steady-state values of a stabilized output quantity lying between specified limits of deviation from a preset value, e.g. a nominal value.

### total direct voltage regulation

    The direct voltage regulation including the effect of the AC system impedance.

### total harmonic distortion THD

    The ratio of the rms value of the harmonic content of an alternating quantity to the rms value of the fundamental component of the quantity.

### turn-off arm

    An auxiliary arm which temporarily takes over the current directly from a conducting valve arm, consisting of one or more latching valve devices which cannot be turned off by a control signal.

### two-quadrant converter

    An AC/DC or DC converter with two possible directions of DC power flow associated with one direction of direct current and two directions of direct voltage or vice versa.

## U
### uniform connection

    A connection with either all principal arms controllable or all principal arms non-controllable.

## V
### valve device assembly

    An electrically and mechanically combined assembly of electronic valve devices or stacks, complete with all its connections and auxiliaries in its own mechanical structure.

### valve device blocking

    An operation to prevent further turn-on of a controllable valve device or an arm consisting of such devices by inhibiting the control signals.

### valve device commutation

    A method of self-commutation in which the commutating voltage is created by turning off the conducting electronic valve device by a control signal.

### valve device quenching

    A method of quenching in which the quenching is performed by the electronic valve device itself.

### valve device stack

    A single structure of one or more electronic valve devices with its (their) associated mounting(s) and auxiliaries if any.

### voltage stiff AC/DC converter

    An electronic AC/DC converter having an essentially smooth voltage on the DC side provided e.g. by a low impedance path for the harmonic currents.

### voltage fed inverter

    A voltage stiff inverter.