# Magnetising circuit parameters in a 3ph induction motor

• Engineering
In summary, the conversation discusses determining the total losses for friction and windage, as well as the no load magnetising current and the values of Ro and Xo in an equivalent circuit. The speaker has plotted a graph and estimated the losses to be 220w, but is unsure about calculating the magnetising current and the values of Ro and Xo. They suggest using the equations I(ph) = I(line)/ROOT3, Vph = V(line)/ROOT3, Pph = P(line)/ROOT3, and cos THETA = P/V*I to find Ro and Xo. They also mention the possibility of replacing the power value with the total losses for friction and windage, which is 250w.

## The Attempt at a Solution

Stator Line voltage 220 164 112 88 42
Stator Line Current 6.8 5.4 3.9 3.8 3.7
Stator power 470 360 278 244 232

By plotting a suitable graph from these results, determine the total of windage and friction losses, the no load magnetising current Io (assume no load current Io is magnetising losses) and the equivalent circuit magnetising circuit parameters Ro and Xo.

I have plotted the graph and estimated that the losses for friction and windage is 220w. I am unsure as to how to calculate the magnetising current and therefore the values of Ro and Xo.I(ph) =I(line)/ROOT3 = 3.93A
Vph =V(line)/ROOT3 = 127.02v
Pph = P(line)/ROOT3 = 127.02w
cos THETA = P/V*I = 75.5deg, Lag
Ro = V/IcosTHETA =129.09Ohm
Xo = V/IsinTHETA = 33.38Ohm

Or do I replace the power value with Total losses-friction and winding losses which equals 250w

Any help in the right direction would be ace.

Last edited by a moderator:
Hi justadaftspark, how did you work out the friction and windage losses. the lessons don't show me the equation.

## 1. What is a 3-phase induction motor?

A 3-phase induction motor is a type of electric motor that operates on a three-phase power supply. It is commonly used in industrial and commercial applications due to its high efficiency and reliability.

## 2. Why is it important to consider the magnetising circuit parameters in a 3-phase induction motor?

The magnetising circuit parameters, such as stator and rotor winding inductances, affect the performance of a 3-phase induction motor. These parameters determine the motor's ability to produce torque and its overall efficiency.

## 3. How do the magnetising circuit parameters impact the motor's performance?

The magnetising circuit parameters determine the amount of flux produced by the motor, which in turn affects the motor's torque and speed. Higher values of inductance result in a stronger magnetic field and therefore, a higher torque output.

## 4. Can the magnetising circuit parameters be adjusted or controlled?

Yes, the magnetising circuit parameters can be adjusted by changing the design of the motor or by using external control methods such as variable frequency drives. However, these adjustments may also affect other aspects of the motor's performance.

## 5. How do you measure and calculate the magnetising circuit parameters in a 3-phase induction motor?

The magnetising circuit parameters can be measured using specialized equipment, such as an impedance analyzer. They can also be calculated using mathematical models and simulations based on the motor's design and operating conditions.

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