Why are potentiometers not a good method of speed control

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SUMMARY

Potentiometers are not an effective method for speed control in electric motors due to significant energy losses and poor speed regulation. For instance, using a potentiometer with a 200V, 1HP motor results in increased current, leading to higher I²R losses and decreased efficiency. Additionally, the limitations of voltage adjustment can cause insulation issues and flux weakening. While Scalextric speed controllers demonstrate a practical application, their poor regulation is only acceptable due to the short lap times involved.

PREREQUISITES
  • Understanding of electric motor efficiency and losses
  • Knowledge of I²R losses in electrical systems
  • Familiarity with voltage regulation and insulation ratings
  • Experience with speed control methods for electric locomotives
NEXT STEPS
  • Research alternatives to potentiometers for motor speed control, such as PWM (Pulse Width Modulation)
  • Learn about the design and application of series resistors in electric locomotives
  • Explore the specifications and performance of Scalextric speed controllers
  • Investigate the impact of voltage adjustments on motor performance and insulation integrity
USEFUL FOR

Electrical engineers, motor control specialists, and hobbyists interested in optimizing motor efficiency and speed regulation methods.

rehaan
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Why are potentiometers not a good method of speed control(in terms of energy)?
 
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there will be huge loss in terms of energy thereby decreasing the efficiency of the motor. for example consider 200V, 1HP motor. if you decrease the voltage by potentiometer current will increase for same HP...which increased I^2R loss...you cannot increase the voltage beyond rating because this will cause insulation problem and flux weakening...
 
Aside from the obvious wasted power, speed regulation is poor.
 
and also finding ones that have any significant power handling capibility is difficult and expensive
 
davenn said:
and also finding ones that have any significant power handling capibility is difficult and expensive
Scalextric speed controllers are a cheap and cheerful example but, because of the short lap times involved, the bad regulation doesn't matter and the player can compensate with skill.
Speed control of large electric locomotives used to be achieved partly with series resistors. Those resistors were fearsome looking but I think the resistances were switched with a large brass wiper and brass contacts, rather than constantly variable.
 
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