Induction motor higher starting torque

In summary, Bob's two induction motors have different starting torques because their starting currents are different.
  • #1
I_am_learning
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After a refresher about basic principle of Induction motor, I realized that the torque developed by induction motor is
[tex]\tau[/tex] = P[tex]{gap}_[/tex] / [tex]\omega[/tex][tex]{s}_[/tex]

Where P[tex]{gap}_[/tex] is amount of power crossing air gap from the stator to the rotor.

In case of wound rotor motors, starting torque can be increased by temporarly connecting external resistors in the rotor winding. However no such method is available in case of squiral cage.
I am currently thinking that keeping in view the above equation, it should be possible to increase the starting torqe by decreasing [tex]\omega[/tex][tex]{s}_[/tex]. So, it decrease it, no of poles should be increased. Although I haven't currently thought of specific winding and switching mechanisim, do you think it might be possible to achieve higher starting by say temporarly switching a 2-pole machine to 4-pole machine during starting?

Edit: sorry for the misaligned 'latex'. I tried but couldn't make it work. Why do you call it latex? Because you use latin words? And also isn't the admin reasearching on more intutive and easier method for 'latex'. Sorry, if I questioned things out of my business.
 
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  • #2
I am using a 1/4 HP 4-pole repulsion-start, induction-run motor on a buffer/grinder, and a 1/2 HP repusion start, induction run motor on a 14" bandsaw. One (Century Electric, patent date 1915) has a radial commutator (see picture). It has higher torque and lower starting current than a similar capacitor-start motor. The repulsion-start motors have a second squirrel cage that is selectively shorted by the brushes on the repulsion-start commutator.

RE Latex- I think it stands for Los Alamos tex. Test your equations at

test Latex equations here http://www.equationsheet.com/textoimage.php

Is this what you mean?

[tex]\tau = \frac{P_g_a_p}{\omega s}[/tex]

Is P the power per pole (the total power divided by the number of poles)?

Bob S
 

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  • #3
P is the TOTAL power crossing the air gap from stator to the rotor i.e. Total input power less the stator losses.
 

What is an induction motor?

An induction motor is a type of electric motor that converts electrical energy into mechanical energy. It operates on the principle of electromagnetic induction, where a rotating magnetic field is created by the interaction of the stator and rotor.

What is higher starting torque?

Higher starting torque refers to the ability of an induction motor to produce more torque at the start of operation. This is important for applications where the motor needs to start with a heavy load or when there is a need for quick acceleration.

How is higher starting torque achieved in an induction motor?

Higher starting torque can be achieved in an induction motor by using a wound rotor with additional resistance, a double cage rotor design, or by using a variable frequency drive (VFD) to control the speed and torque of the motor.

What are the advantages of an induction motor with higher starting torque?

An induction motor with higher starting torque has the ability to start and operate with heavy loads, reducing the chances of stalling or tripping. This can also lead to increased efficiency and reduced energy consumption.

Are there any drawbacks to using an induction motor with higher starting torque?

One potential drawback of using an induction motor with higher starting torque is that it may have a higher initial cost due to the need for additional components or a more complex design. Additionally, the increased torque may also put more strain on the motor and lead to a shorter lifespan.

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