Doubly Fed Induction Motors (Part 1 of 2)

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In this lesson we'll learn to repurpose a regular wound rotor induction motor as a doubly fed induction motor. We'll examine regular and flip flopped versions of induction and synchronous mode and introduce hyposynchronous and hypersynchronous operation. We'll learn that a rotating magnetic field on the rotor traveling in the same direction as the stator will allow operation below normal synchronous speed. Conversely we'll learn that a rotating magnetic field on the rotor traveling in the opposite direction as the stator will allow operation above normal synchronous speed. Finally, we'll examine the effect of field current variation in a doubly fed induction motor while in operation. (Part 1 of 2)
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Опубликовано:

11 фев 2024

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Комментарии : 8

@koffibanan3099 5 месяцев назад

Wow, I had no idea about these configurations, neat! Thanks Jim

@almfreak 5 месяцев назад

Pretty cool configuration! I’m going to guess in part 2 we’ll see if you could rotate the magnetic fields in opposite directions and get higher RPM in a hypersynchronous mode of operation?

@bigbadtech 5 месяцев назад

Dude I'm editing part 2 right now. Are you looking over my shoulder?

@donberg01 5 месяцев назад

I never heard of a "hypo synchro" motor, can you please explain WHERE you would use this feature?

@bigbadtech 5 месяцев назад

I deliver the punchline in part 2 ... it's all about speed control and money. Rather than using an expensive oversized AC to AC converter on a squirrel cage induction motor one can use a smaller cheaper AC to AC converter on just the rotor of a DFIM to step up or down speed. Wait till you check out generator mode!

@evanjohnson1927 5 месяцев назад

Im an electrical engineer at a facility that uses a large doubly fed induction motor. We use a Kramer motor generator system as an AC/AC converter. There is one thing that I don't understand during start up we have to get the rotor frequency to 60 hz and sync before closing the stater field breaker. The currents on the rotor are very large why does this not cause excessive hearing in the rotor windings? for scale its a 20k horse power motor and the rotor currents are 1100- 1300 amps before sync are those windings not acting like resistors?

@almfreak 5 месяцев назад

I’m NOT an electrical engineer, but I believe those motor windings are behaving like an inductive load, not a resistive load. Kindof like a transformer. My guess on why they would need to synchronize the rotor frequency before closing the stator breakers is because the motor is stationary and you want the fields rotating in synch so that when the breakers close, the motor doesn’t try to instantly jump full speed. If you start the rotor and stator fields in synch at 60Hz and the slowly desynchronize it will start the motor 0 RPM and slowly ramp up as the rotor and stator frequency differential increases.

@bigbadtech 5 месяцев назад

Yes, presumably this is kind of like a soft starter in reverse. Rather than ramping stator frequency up to 60 one instead ramps rotor frequency from 60 down.