Appendix I. Some Electrical and Metallic Rectifier Terminology [Metallic Rectifiers (1957)]

Aging. Aging of a metallic rectifier is any persisting change (except failure) which takes place for any reason in either the forward or reverse resistance characteristic. (NEMA) Ambient Temperature. Ambient temperature is the air temperature immediately around the metallic rectifier.

Asymmetrical Conductor. See rectifier cell.

Cell Combinations. The cell combination in a metallic rectifier is the arrangement of cells in a stack, stack assembly, or rectifier unit. The cell combination is described by a sequence of three numbers, written a-b-c, with the following significances:

a. Number of rectifying elements.

b. Number of cells in series in each rectifying element.

c. Number of cells in parallel in each rectifying element.

NOTE: The total number of cells in the rectifier is the product of these three numbers. (NEMA) Cell Current Rating. The current rating of a metallic rectifier cell is the maximum current that may be passed through it in the forward or low resistance direction and maintain its thermal ratings.

Cell Voltage Rating. The voltage rating of a metallic rectifier cell is defined as the maximum rms value of an AC voltage to be applied to the cell.

Conductor. Substances in which the electrons are able to pass readily from atom to atom under the influence of a small applied potential are called conductors. Examples of conductors are silver, copper, aluminum, etc.

Conversion Efficiency of Metallic Rectifier. The conversion efficiency of a metallic rectifier equals the average DC volts times the average DC amperes output, divided by the AC watts input, in percent.

Dry Disc Rectifier. See metallic rectifier.

Dry Plate Rectifier. See metallic rectifier.

Electric Current Flow. The conventional direction of electric current flow in the circuit external to the applied potential is from the positive to the negative terminal.

Electron Flow. In a circuit the electron flow is from the negative terminal of the applied potential to its positive terminal.

Fin. A square or round metal plate which may or may not perform an electrical function in a rectifier stack, but is assembled therein for the purpose of dissipating heat.

Forward Current. The current which flows in the forward direction through a rectifier cell.

Forward Direction. The forward direction of a rectifier cell is the direction of lesser resistance to current flow through the cell.

Forward Resistance. The forward resistance of a metallic rectifier is the resistance measured at a specified forward voltage drop or forward current.

Forward Voltage Drop. The forward voltage drop is the potential drop in the rectifier cell as a result of the flow of for ward current through the metallic rectifier cell.

Instrument Rectifier. An instrument rectifier is a specialized metallic rectifier having smaller disc area than conventional power supply units and being especially processed to have stability, permanence, and high efficiency.

Insulator. Substances in which the electrons are so tightly bound that it takes enormous electric potential to cause current flow are called insulators. Examples of insulators are ceramics, glass, and mica.

kva. A unit of apparent electrical power equal to 1000 volt amperes, abbreviated from kilovolt-amperes.

kw. Abbreviation for kilowatts, equal to 1000 watts.

Metallic Rectifier. A metallic rectifier is a rectifier which has an asymmetrical conductive junction between solid con ducting and semiconducting materials which permits current flow more readily in one direction.

Metallic Rectifier Unit. A metallic rectifier unit is an operable arrangement of a rectifier and essential auxiliaries such as transformers, filters, switchgear, etc. (NEMA) Non-symmetrical Conductor. See metallic rectifier.

Power Factor (pf). Power factor is the ratio in percent of the AC watts input to the product of the AC volt-ampere input.

Rectifier. A rectifier is an electrical device which changes alternating current into direct current by its characteristic which permits the flow of current more readily in one direction.

Rectifier Assembly. A metallic rectifier stack assembly is an assembly of two or more stacks.

Rectifier Cell. A single junction rectifier which has one positive electrode, one negative electrode, and one rectifying junction and is operable as an elementary rectifier.

Rectifier Couple. See rectifier cell.

Rectifier Disc. See rectifier cell.

Rectifying Element. See rectifier cell.

Rectifying Junction. The rectifying junction is the region in a rectifying cell which possesses asymmetrical conduction.

This junction is also called the barrier layer or blocking layer.

Rectifier Plate. See rectifier cell.

Rectifier Stack. A rectifier stack is an assembly of one or more rectifier cells. Rectifier stacks are usually made by assembling rectifier cells upon an insulated center bolt or stud.

Rectifier Valve. A metallic rectifier whose function is to block the reverse flow of direct current for control or similar purposes.

Reverse Voltage. The reverse voltage is the voltage which is applied in the reverse direction to a metallic rectifier cell.

Reverse Current. The reverse current is the current which flows in the reverse direction through the rectifier cell. It is also called the leakage current.

Reverse Direction. The reverse direction of a metallic rectifier cell is the direction of greater resistance to current flow through the cell.

Reverse Resistance. The reverse resistance of a metallic rectifier cell is the resistance measured at a specified re verse voltage or reverse current.

Root-Mean-Square (rms). The effective value of sinusoidal waveform of alternating current or voltage and equal to 0.707 times the peak value of the sine wave.

Semiconductor. Substances which are not good conductors and yet are not insulators are called semiconductors. Examples of semiconductors are carbon, metal oxides, and certain alloys.

Semiconductor Rectifier. See metallic rectifier.

Single-Phase. The form of distribution of alternating current commonly used for household purposes and small power applications.

Three-Phase. A form of distribution of alternating current commonly used for commercial and industrial purposes; the voltage across each phase is at an angle of 120 degrees to the voltage across the other phases.

Threshold Voltage. The threshold voltage of a metallic rectifier cell is the minimum value of alternating voltage applied to the cell before rectification takes place.

Unilateral Conductor. See rectifier cell.

Varistor. See metallic rectifier.

Voltage Regulation. Voltage regulation is the ratio of the difference between the no load voltage and the full load voltage to the full load voltage in percent.

Waveform Factor. The waveform factor is the ratio between the rms to the average value of the waveform. The waveform factor of a sine wave is 1.11.