Concept explainers
It is necessary to reduce the voltage applied to an induction motor as the frequency is reduced from the rated value. Explain why this is so.
Answer to Problem 16.1P
To keep the ratio of voltage to frequency constant, it is necessary to reduce the voltage applied to an induction motor as the frequency is reduced from the rated value.
Explanation of Solution
Given Information:
It is necessary to reduce the voltage applied to an induction motor as the frequency is reduced from the rated value.
Consider the EMF equation for the induction motor:
where
Therefore, the induced EMF is directly proportional to flux and frequency:
Now, if the frequency is reduced, the magnitude of the induced EMF will also be reduced such that to maintain constant airgap flux.
Consider the applied voltage to the induction motor is V, such that, this applied voltage V is directly proportional to induced EMF E, i.e.,
Therefore, if the frequency is reduced to maintain the constant flux in the air gap, there must be a proportional reduction in the magnitude of the applied voltage.
If the applied voltage is not reduced in proportion to the frequency, it results in excessive motor currents which may cause damage to the motor. Due to this, losses increase, and therefore, the efficiency of the motor is reduced.
So, it is necessary to reduce the voltage applied to an induction motor as the frequency is reduced from the rated value.
Conclusion:
It can be concluded that it is necessary to reduce the voltage applied to an induction motor as the frequency is reduced from the rated value to maintain constant flux in the airgap.
Want to see more full solutions like this?
Chapter 16 Solutions
Electrical Engineering: Principles & Applications (7th Edition)
- IV. What are the various losses in an induction motor? On what actors do they depend?arrow_forwardanalyze 3 commonly used ac motor starting methods using suitable diagrams and torque-speed curvesarrow_forwardA 220-V-rms (line-to-line), 60-Hz, three-phase induction motor operates at 3500 rpm while delivering its rated full-load output power. Estimate the no-load speed and speed regulation for the motor.arrow_forward
- Consider the AC circuit shown in the image, that is driven by a voltage V=V0cos(ωt). a) What is the current through the capacitor, C? Give its amplitude and phase relative to the drive voltage. b) What is the total current through the voltage source? Again require amplitude and phase relative to the drive voltage.arrow_forwardDesign a hybrid powertrain which can be run both at series and parallel hybrid operation modes. Explain the operation of the system. Sketch the power flow paths for each mode.arrow_forwardExplain briefly the differences of induction motor & synchronous motor. 6 sentencearrow_forward
- Find the stability condition of the equation given below for the characteristic equation. (To be stable acoefficients should be in what range, what kind of conditions should it meet, etc.)(Using the Routh-Hurwitz criterion(according to the requirements and qualification conditions).arrow_forwardHow do you do Routh Houritz criteria? What is a method that always works? Like how apply to below?arrow_forward1. Explain the stability analysis of a DC system in detailarrow_forward
- Suppose that you were an engineer planning a new electric co-generation facility for a plant with excess process steam. You have a choice of either two 10 MW turbine-generators or a single 20 MW turbine generator. What would be the advantages and disadvantages of each choice? (Note: Ans with detail hand writing.) step by step and headingsarrow_forwardWrite a summary (points) about the stator resistance test of the squirrel cage induction motor .arrow_forwarda) What applications / experiments are necessary to find the Rc parameter in the equivalent circuit given in Figure 1? b) Write the value of the Ir 'current given in Figure 1 with a sentence in the idle running test of the 3-phase Asynchronous motor.arrow_forward
- Power System Analysis and Design (MindTap Course ...Electrical EngineeringISBN:9781305632134Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. SarmaPublisher:Cengage Learning