The discussion revolves around the operation of a magneto in aviation, specifically focusing on the generation of AC current from a physical magnet and its subsequent effects on the primary and secondary windings. Participants seek to clarify the workings of the magneto, including grounding issues and the role of contact points in the circuit.
Participants express differing views on the grounding of the primary winding and the implications of the contact points opening. There is no consensus on the correct interpretation of the circuit behavior when the contact points are opened, indicating ongoing debate and uncertainty.
Participants highlight potential misunderstandings regarding the grounding of the primary winding and the behavior of current flow when contact points open, suggesting that assumptions about circuit completeness may vary.
Thank you for your reply.Drakkith said:
Is there a diagram that goes with your explanation? Use the "Attach files" link at the lower left of the Edit window to upload the diagram.EdgarW said:
According to this diagram and several more, the primary winding has one end directly grounded and the other end grounded through the condenser/breaker circuit, as shown above. Assuming that 'points' means the contact points on the distributor, then they have nothing to do with the primary winding.EdgarW said:
Looks to me like it is the secondary winding that connects to the points on the distributor.EdgarW said:
Let me see if I can simplify my concern:Drakkith said:
When the contact breaker is opened, there isn't a complete circuit anymore. The current can't go through the capacitor (condensor) and it can't come from or go to the other ground, as there would quickly be a buildup of charge in the disconnected side that would stop it.EdgarW said:
That diagram is missing something, I think. The magneto on my old motorcycle had a physical linkage (same shaft) between the magnet and coils and the breaker 'points'. This times the breaking of the circuit with the appropriate part of the varying field around the coil. Breaking the circuit at the right time produces a far higher voltage than just having 'AC'. Automatic advance of the spark was achieved by flying weights that changed the angle of the plate holding the points. (No vacuum advance, though)EdgarW said:
What exactly do you mean by, "use the ground"? Current will flow in a loop, going into/out of either ground in order to make that loop. So when current flows into the ground at one end of the primary winding, it will flow out of the ground at the other end. Same for the secondary.EdgarW said:
Is this just a matter of semantics? "Ground" is a term often used to describe the nearest large conducting object - for example, the car, plane or equipment chassis in which the Potential Difference between all connected points is (near enough) 0V. The assumption can easily fail when alternating voltages are involved.Drakkith said:
Small single engine aircraft use the magneto system because it allows the plane to keep flying even if the rest of the electrical system fails. In fact, they have two magnetos. You typically use both, but the engine will run on just 1, allowing you to make it to an airport. One of the pre-flight checks is to switch between running on 2 and 1 magnetos, to insure both are working.sophiecentaur said:
Too right; the electric charge budget can be really stingy.Janus said:
No, I don't think so. The phrasing used by the OP suggests that he thinks that only one ground is being used at a time, and I want to make sure I'm understanding what he is saying.sophiecentaur said:
We can't know but I look at the thread title with the word 'aviation'. That implies the OP could be thinking there's something special about the Earth, other than the term 'earth' meaning a common reference point - with an abritrary zero origin. Planes can't be connected to The Earth but the magneto works the same wherever it is.Drakkith said: