Glossary of Terms (Refers to automotive charging and start- ing systems, prepared by JIMCO, Inc.) “A” Circuit — Alternators: The reg- ulator acts as a switch electrically con- nected between the field coil (rotor) and system negative (-). “A” Circuit — Generators: The reg- ulator acts as a switch electrically con- nected between the field terminal and the return output terminal (ground). Typically one end of the generator field is connected to the field terminal and the other internally to the “insulated” output armature brush. AC — Alternating current: Electrical current which flows in one direction and then reverses itself during each cycle. Automotive alternators produce AC current which is rectified to DC. Normal household current is 110-120 volt AC at 60 cycles per second. AC Wave Form — See sine wave. Alternation — One half of an AC sine wave, either the positive or negative half. Ampere — The electrical unit which specifies the amount of current flow. This is measured with an ammeter. The sym- bol for current is “I” although “A” for amp is commonly used. For purposes of comparison using water flow, amperes would be like gallons per minute. Ammeter — The meter used to mea- sure current flow. An ammeter must be connected in series with the current flow, either in the supply or return path. Milliammeters are sensitive meters for reading less than one amp. Armature — The rotating part of a generator that produces current. Anode — One of the terminals on a diode. A term derived from vacuum tubes. Avalanche diode — A semiconductor which passes current in the forward direction and blocks current flow in the reverse direction, the same as conven- tional diodes. It also has the ability to conduct current in the reverse direction when the voltage across the diode exceeds its “avalanche” voltage. For pur- poses of comparison using water flow, an avalanche diode is like a check valve combined with a pressure relief valve. “B” Circuit — Alternators: The reg- ulator acts as a switch electrically con- nected between the field coil (rotor) and system positive (+). “B” Circuit — Generators: The regulator acts as a switch electrically connected between the field terminal and the “insulated” output terminal (arma- ture). Typically one end of the generator field is connected to the field terminal and the other internally to the return “grounded” armature brush. Battery — A device which stores energy in chemical form. Automotive lead acid batteries furnish DC electrical current. Battery Voltage — The voltage of a fully charged battery. 6 volt battery: 6.0 to 6.5 volts; 12 volt battery: 12.0 to 13.0 volts; 24 volt battery (batteries): 24.0 to 26.5 volts; 32 volt battery (batteries): 32.0 to 35.0 volts. Brush — A device which makes the electrical contact to the commutator on the armature of a DC generator or to the slip rings on the rotor of an alternator. Brushless — An alternator without rotor brushes. The field coil winding is mounted to the end frame (non-rotating). A specially constructed rotor rotates between the field coil and the stator. Capacitor — A device which stores true electrical energy (electrons). It is typically used in an alternator as a “shock absorber” to reduce harmful voltage spikes and to reduce radio interference. Also referred to as “condenser.” Carbon Pile — Operator controlled variable resistive electrical load. It is used in a JIMCO test bench to provide the load while testing a generator or alternator. Case Ground — An alternator or gen- erator with one of its output terminals connected to the case of the unit as in negative or positive ground. Cathode — One of the terminals on a diode. A term originally from vacuum tubes. Charge — A non-quantitative term meaning that an alternator or generator is producing voltage and amperage. Charging System Voltage — The voltage of a generator or alternator. The voltage necessary to charge the vehicle battery. The voltage regulator set point. Typical charging system voltage for 6 volt system: 7.0 to 7.5 volts; 12 volt sys- tem: 14.0 to 15.0 volts; 24 volt system: 27.5 to 28.5 volts; 32 volt system: 37.5 to 39.0 volts. Circuit — A complete path for current flow consisting of a source and load. The path includes both a supply path and return path. Clockwise — Clockwise rotation of an alternator or generator when viewing the pulley end. Counterclockwise — Counterclock- wise rotation of an alternator or generator viewing the pulley end. Coil — Many turns of wire, usually on an iron core as in a stator coil or rotor coil. Common — Two or more electrical components electrically connected to the same point. Commutator — That part on the armature of a DC generator which mechanically rectifies the AC current produced in the armature to DC current. Complete Circuit — Same as circuit. Conductor — Material that efficiently passes electrical current. Automotive wire is a conductor. Current — The movement of electri- cal energy. For purposes of comparison current is the