How Does Reactive Load Affect Alternator Speed?

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Discussion Overview

The discussion revolves around the effects of reactive loads on the speed of a motor-driven alternator. Participants explore the implications of power consumption by different types of loads, specifically focusing on scenarios with nonzero and zero power angles (δ). The conversation includes theoretical considerations and implications for practical applications.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant suggests that an alternator slows down when connected to a local load due to power consumption, implying a relationship between power angle δ and alternator speed.
  • Another participant argues that with a purely reactive load (δ = 0), the alternator should not slow down because there is no net energy delivery to a consumer.
  • It is noted that a reactive component consumes energy during the first half of a cycle but returns it in the next half, leading to a discussion about whether this results in a net change in speed.
  • Some participants contend that while power is consumed in the first half cycle, the alternator will not experience a change in velocity over time due to the cyclical nature of reactive power.
  • There is a challenge regarding the interpretation of reactive power and its implications for the alternator's operation, particularly in relation to the charging of capacitors.

Areas of Agreement / Disagreement

Participants express differing views on whether a purely reactive load affects the speed of the alternator. There is no consensus on the implications of reactive power and its effect on the alternator's velocity.

Contextual Notes

Participants discuss the cyclical behavior of reactive loads and the assumptions regarding energy consumption and delivery, but these aspects remain unresolved and depend on specific definitions and interpretations of reactive power.

cnh1995
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A motor driven alternator connected to local load (in lab), say a lamp bank, slows down due to power consumption by the load I.e. nonzero power angle δ. But should it slow down when δ is zero i.e. with purely reactive load(like in SC test and ZPF test)?
 
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cnh1995 said:
should it slow down when δ is zero i.e. with purely reactive load
No it shouldn't, because it cannot deliver energy anywhere ( nobody to consume it ).

A reactive component will consume energy as for one half of a period ( charge a capacitor / induce current in an inductor ), but the energy will be returned it in the next half.
 
But if it consumes power in the first half cycle, shouldn't it slow down?
 
cnh1995 said:
But if it consumes power in the first half cycle, shouldn't it slow down?
Yes, but it will speed up again in the next half cycle. So over time it will not change velocity.

Of course you could say, that the motor will be halted completely within a half periode, because it must charge a capacitor, but then the term "reactive power" does not make sense any longer.
 

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