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Ignition Coils

Ignition Coils

An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system which transforms the battery's low voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel.


An ignition coil consists of a laminated iron core surrounded by two coils of copper wire. Unlike a power transformer, an ignition coil has an open magnetic circuit - the iron core does not form a closed loop around the windings. The energy that is stored in the magnetic field of the core is the energy that is transferred to the spark plug.


Current technology coils are of several basic types, say, pencil coils. Pencil coils are typically an inch in diameter and up to four inches long. These coils are designed to fit in between the cams of DOHC (double overhead camshaft) and SOHC (single overhead camshaft) engines. The normal practice for pencil coils is to include the switching electronics needed to control the coil, in a small pocket near the outer end of the coil package. 

Characteristics (magnetic application):


In a spark plug ignition assembly for a spark plug, an ignition coil assembly has a steel laminated core, said core having a first core portion and a second core portion, and a primary winding around the first core portion and a secondary winding around the primary winding. A spark plug connecting member is provided for connecting the coil assembly to the spark plug. At least one of the first and second core portions has a slot therein with a magnet located in the slot.


Applied Magnetic Materials:



1.Elevated Temperature NdFeB including UH, EH and AH grades.

2.High Hcj (intrinsic coercive force) SmCo, like SmCo 26H, SmCo 28H, SmCo 30H. Generally, Hcj (intrinsic coercive force) of these magnets is greater than 18 kOe.



1.Disc: diameter ranges from 5mm to 20mm, thickness from 0.7mm to 1.8mm

2.Rectangular: length/width ranges from 8mm to 20mm, thickness from 0.7mm to 1.8mm



Magnetic property:

A.Demagnetization curves in room temperature and designated high temperature

B.Hk: demagnetization field that reduces the remanence (Br) by certain amount in accordance to requirement

Supporting Equipment: Hysteresisgraph


B.Irreversible demagnetization by comparing

1.Magnetic flux in room temperature

2.Magnetic flux after magnets are heated in elevated temperature

Supporting Equipment: flux meter, industrial oven


Important: The consistency of the flux is critical and matters even more. Vector Magnets possesses strict control of flux test for ignition coil magnets so as to ensure the ignition coil would obtain the best possible performance.

Appearance and dimensions



Salt Spray Test: set in certain humidity, PH based on application

Plating/Coating thickness; using x-ray-fluorescence to analyze the thickness of surface plating/coating.

Supporting Equipment: Salt Spray Test Cabinet; XRF analyzer,



1.Geometric tolerances (e.g. parallelism, perpendicularity, flatness, etc)

2.Desired size and shape