Coil Group - a number of adjacent coils in the same phase. A coil group lies between other coil groups which are in different phases. The number of groups is equal to the number of poles multiplied by the number of phases.
Coil Span - the number of slots spanned by a coil. For example, a coil span of 5 is the same as the coil throw 1-6. Refer to Illustration 6.
Coil Throw - the distance between the two sides of the coil, which is expressed by numbering the slots that the two sides of the coil occupy. For example, a coil with a coil throw 1-6 would occupy the two extremes of a slot sequence that is numbered 1-6. Refer to Illustration 6.
Coils Per Group - This parameter shows how many coils are in any specified group. Coils/Group can be calculated by dividing the total number of coils by the number of groups.
Concentric Winding - In a concentric winding, each coil group comprises coils of different spans which are sharing a common center line. Thus, coils are routed in loops that are enclosed within larger loops. Therefore, the coil throw may be expressed as a decimal number. This method of winding requires the least amount of copper and results in slightly higher levels of harmonics. Refer to Illustration 4.
Copper Weight - total weight of the wire.
Exciter Frequency - exciter armature operating frequency.
Exciter Poles - number of magnetic poles in the exciter field.
Field Lead Resistance at 25 °C (77 °F) - resistance measured at the lead terminals of the field.
HF - an abbreviation for heavy film wire.
Group - same as coil group.
Inside Connection - the number of stator coils in each phase and the coil connections needed to make up one phase for a high voltage star configuration.
Insulation - There are two main types of wire insulation that are used on Caterpillar generators: Heavy Polyester Polyamide Imide and Heavy Nytherm. These insulation types can be either class H or class F materials. Class H is temperature rated at 180 °C (356 °F). Class F is temperature rated at 155 °C (311 °F).
Lap Winding - a winding in which one side of each coil, where it emerges from each end of the slot, lies above the nearest coil. The opposite side of the coil lies underneath the nearest coil. Lapped windings are routed across one another. The coil throw is a whole number. This method of winding provides a better waveform because of better symmetry. Refer to Illustration 5.
Layer (Form) Wound - method of placing large single wires in uniform and in parallel layers. Layer winding utilizes square, rectangular, or round wires which can be placed very close to one another resulting in superior efficiency and durability. Refer to Illustrations 2 and 3.
Line Lead - an output cable that is used to make external connections.
Low Voltage Connected Line to Line Resistance at 25 °C (77 °F) - low voltage star connected phase to phase resistance. For example: (T1 and T7 to T2 and T8), (T2 and T8 to T3 and T9), (T3 and T9 to T1 and T7).
Mean Length Turn (M.L.T.) - the average length of all the turns in the winding.
Number and Size of Line Leads - the quantity and cross section area of the output leads. The wire size of the line leads is listed according to the American Wire Gauge (AWG).
Pitch - The winding pitch is the ratio of the coil span to the span of the poles. The formula for the pitch is the following: Pitch = (Coil Throw-1) / (Slots/Poles)
Pole - number of magnetic poles in the field.
PM Frequency - the output frequency of the permanent magnet (PM) generator.
Random Wound - method of placing several small wires in uniform and in parallel layers. Each wire is randomly placed and can overlap the other while being wound. Random windings utilize coils of round wire. Refer to Illustration 1.
RD - an abbreviation for round wire.
Slot - A slot is the groove in the lamination. The number of slots is equal to the number of coils. Refer to Illustration 6.
SQ - an abbreviation for square wire.
Stack Height (Length) - the length or the height of the lamination stack. Refer to Illustration 6.
Terminal Bolt Size - The diameter of the bolt which is used to connect line lead together.
Turns Per Coil - number of times each coil is wrapped around the slot or how many turns of wire in each coil.
Turns Per Pole - how many turns of wiring on each pole.
Windings - layers of wire on a core. The winding process can be broken into two types: the routing of coils and the winding type. The routing of coils can be either concentric or lap. The winding type can be either random or layer (form).
Wire No. and Size - The wire number shows how many wires should be used to form a single coil. The wire size is given according to the American Wire Gauge (AWG).
 | |
| Illustration 1 | g00728357 |
Random Wound Wiring - Typical Example | |
 | |
| Illustration 2 | g00728361 |
Layer (Form) Wound Wiring Using the Round Wire - Typical Example | |
 | |
| Illustration 3 | g00728371 |
Layer (Form) Wound Wiring Using the Square Wire - Typical Example | |
 | |
| Illustration 4 | g00728363 |
Concentric Winding - Typical Example | |
 | |
| Illustration 5 | g00728366 |
Lap Winding - Typical Example | |
 | |
| Illustration 6 | g00728367 |
Stator - Typical Example (1) Slot (2) Stack length (height) (3) Coil Throw (4) Coil | |