From textbook, it is stated that Kv = rpm/V. But how does Kv change with temperature mathematically?
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1You'd have to look at a specific motor data sheet to find that out or, try and figure out what magnets they use and how the magnet material flux density changes with temperature. – Andy aka Aug 09 '23 at 19:05
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Rate of temperature change? or just at working temp? – Solar Mike Aug 09 '23 at 19:25
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@Andyaka May I know what is the mathematical relationship between the magnetic flux, B with Kv, please? – user150518 Aug 09 '23 at 20:27
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In an ideal motor, Kv is independent of temperature.
In a real motor, anything that changes the strength of the magnetic field, and the effective permeability of the magnetic circuit, will alter it.
Some magnets have a strength that is temperature dependent.
Some magnetic materials used for the rotor and field return have a permeability that is temperature dependent.
The size of the air-gap between rotor and field iron may well vary with temperature, especially if the rotor and field run at different temperatures.
Aside from Kv variations, another temperature dependent factor that will affect motor performance is the resistance of the windings, increasing by about 10% for every 25 C temperature rise.
Neil_UK
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Thanks a lot for your answer Neil! If you don't mind, I have some add-on question. Say that the initial magnetic flux is B when Kv = Kv, what would Kv be if the magnetic flux decreases from B to k*B where k is a constant multiplier (0
– user150518 Aug 09 '23 at 20:25 -