Induction Machines Handbook

Steady State Modeling and Performance

Ion Boldea

• Publisher: CRC Press
• Year: 2020
• Topic: Technology & Engineering
• eBook ISBN:
  9781000056730
• Subtopic: Civil Engineering
• Index: Technology & Engineering

Induction Machines Handbook: Steady State Modeling and Performance offers a thorough treatment of steady-state induction machines (IM), the most used electric motor (generator) in rather constant or variable speed drives, forever lower energy consumption and higher productivity in basically all industries, from home appliances, through robotics to e-transport and wind energy conversion.

Chapter 1 offers a detailed introduction from fundamental principles to topological classifications and most important applications and power ranges from tens of W to tens of MW.

Then individual Chapters 2 and 4 deal in detail with specific issues, such as

• Magnetic, electric, and insulation materials
• Electric windings and their mmf
• Magnetization curve and inductance
• Leakage inductances and resistances
• Steady-state equivalent circuit and performance
• Starting and speed control methods
• Skin and on-load saturation effects
• Field harmonics, parasitic torques, radial forces, noise
• Losses
• Thermal modeling
• Single-phase induction machine basics
• Single-phase induction motors: steady-state modeling and performance

Fully revised and updated to reflect the last decade's progress in the field, this third edition adds new sections, such as

• Multiphase and multilayer tooth-wound coil windings
• The brushless doubly fed induction machine (BDFIM)
• Equivalent circuits for BDFIM
• Control principles for doubly fed IM
• Magnetic saturation effects on current and torque versus slip curves
• Rotor leakage reactance saturation
• Closed-slot IM saturation
• The origin of electromagnetic vibration by practical experience
• PM-assisted split-phase cage-rotor IM's steady state

The promise of renewable (hydro and wind) energy via cage-rotor and doubly fed variable speed generators e-transport propulsion and i-home appliances makes this third edition a state-of-the-art tool, conceived with numerous case studies and timely for both academia and industry.

1 Induction Machines

An Introduction

1.1 Electric Energy and Induction Motors

The level of prosperity of a community is related to its capability to produce goods and services. However, producing goods and services is strongly related to the use of energy in an intelligent way.

Motion and temperature (heat) control are paramount in energy usage. Energy comes into use in a few forms such as thermal, mechanical, and electrical.

Electrical energy, measured in kWh, represents more than 30% of all used energy, and it is on the rise. Part of electrical energy is used directly to produce heat or light (in electrolysis, metallurgical arch furnaces, industrial space heating, lighting, etc.).

The larger part of electrical energy is converted into mechanical energy in electric motors. Amongst electric motors, induction motors are most used both for home appliances and in various industries [1–11].

This is so because they have been traditionally fed directly from the three-phase A.C. electric power grid through electromagnetic power switches with adequate protection. It is so convenient.

Small-power induction motors, in most home appliances, are fed from the local single-phase A.C. power grids. Induction motors are rugged and have moderate costs, explaining their popularity.

In developed countries today, there are more than 3 kW of electric motors per person and most of them are induction motors.

While most induction motors are still fed from the three- or single-phase power grids, some are supplied through frequency changers (or power electronics converters) to provide variable speeds.

In developed countries, already 20% of all induction motor power is converted in variable speed drive applications. The annual growth rate of variable speed drives has been 9% in the past decade, while the electric motor markets showed an average annual growth rate of 4% in the same time.

Variable speed drives with induction motors are used in transportation, pumps, compressors, ventilators, machine tools, robotics, hybrid or electric vehicles, washing machines, etc.

The forecast is that in the next decade, up to 50% of all electric motors will be fed through power electronics with induction motors covering 60%–70% of these new markets.

The ratings of induction motors vary from a few tens of watts to 33,120 kW (45,000 HP). The distribution of ratings in variable speed drives is shown in Table 1.1 [1].

TABLE 1.1
Variable Speed A.C. Drives Ratings

Power (kW)	1–4	5–40	40–200	200–600	>600
Percentage	21	26	26	16	11

Intelligent use of energy means higher productivity with lower active energy and lower losses at moderate costs. Reducing losses leads to lower environmental impact where the motor works and lower thermal and chemical impacts at an electric power plant that produces the required electrical energy.

Variable speed through variable frequency is paramount in achieving such goals. As a side effect, the use of variable speed drives leads to current harmonics pollution in the power grid and electromagnetic interference (EMI) with the environment. So power quality and EMI have become new constraints on electric induction motor drives.

Digital control is now standard in variable speed drives, while autonomous intelligent drives to be controlled and repaired via the Internet are on the horizon. And new application opportunities abound: from digital appliances to hybrid and electric vehicles and more electric aircraft.

So much on the future, let us now go back to the first two invented induction motors.

1.2 A Historical Touch

Faraday discovered the electromagnetic induction law around 1831, and Maxwell formulated the laws of electricity (or Maxwell’s equations) around 1860. The knowledge was ripe for the invention of the induction machine (IM) which has two fathers: Galileo Ferraris (1885) and Nikola Tesla (1886). Their IMs are shown in Figures 1.1 and 1.2.

FIGURE 1.1 Ferrari’s induction motor (1885).

FIGURE 1.2 Tesla’s induction motor (1886).

Both motors have been supplied from a two-phase A.C. power source and thus contained two-phase concentrated coil windings 1-1′ and 2-2′ on the ferromagnetic stator core.

In Ferrari’s patent, the rotor was made of a copper cylinder, while in Tesla’s patent, the rotor was made of a ferromagnetic cylinder provided with a short-circuited winding.

Though the contemporary induction motors have more elaborated topologies (Figure 1.3) and their performance is much better, the principle has remained basically the same.

FIGURE 1.3 A state-of-the-art three-phase induction motor. (Source: ABB motors.)

That is, a multiphase A.C. stator winding produces a travelling field that induces voltages that produce currents in the short-circuited (or closed) windings of the rotor. The interaction between the stator-produced field and the rotor-induced currents produces torque and thus operates the induction motor. As the torque at zero rotor speed is nonzero, the induc...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Preface
• Author
• Chapter 1 Induction Machines: An Introduction
• Chapter 2 Construction Aspects and Operation Principles
• Chapter 3 Magnetic, Electric, and Insulation Materials for IM
• Chapter 4 Induction Machine Windings and Their mmfs
• Chapter 5 The Magnetisation Curve and Inductance
• Chapter 6 Leakage Inductances and Resistances
• Chapter 7 Steady-State Equivalent Circuit and Performance
• Chapter 8 Starting and Speed Control Methods
• Chapter 9 Skin and On-Load Saturation Effects
• Chapter 10 Airgap Field Space Harmonics, Parasitic Torques, Radial Forces, and Noise Basics
• Chapter 11 Losses in Induction Machines
• Chapter 12 Thermal Modelling and Cooling
• Chapter 13 Single-Phase Induction Machines: The Basics
• Chapter 14 Single-Phase Induction Motors: Steady State
• Index