Highlights in POLYPHASE INDUCTION MOTORS

Highlights

• In an induction motor, there is an electric transformer in which the present magnetic circuit is separated into two portions. These portions are relatively movable and they are separated just by an air Rap, where one carry the primary winding while the seconf carry the secondary winding.
• Synchronous speed is shown as

N_s – 120f/p

Here, f = frequency

P = number of poles

• Slip, s = (N_s – N)/ N_s 

Where  N = motor speed

• The rotor current frequency can be given as –

fr =  sf, so, f is the supply of requency and s is the sleep.

• Torque T = keR₂E₂ ² / R₂² +S₂X₂²

Now, the starting torque Tst= kR₂E₂ ² / R₂² +X₂²

For the maximum torque condition, s = R₂/X₂

Maximum Torque T_max =  kE₂ ²/2X₂

• Starting Torque ∝ Square of applied Voltage
• T_f/T_m – 2s_fmT/(s²_mT+1)
• T_st/Tmax = 2s_mT/ s²_mT+1
• Rotor Copper loss/ Rotor Gross output = S/ 1-S
• Rotor Outpput/ Rotor Input=  1-S