Electrical Machines 2
AC Machinery Fundamentals
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Preview
After the discussion, the students must be able to:
1. Understand and be familiar with the terms and ideas in AC
Machinery.
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Electrical Machines
Machines used for converting energy from one form to
another. [1]
Table 1 Common Electrical Machines
(AC)
Machine
From
(Energy)
To
(Energy)
Generator
Mechanical
Electrical
Transformer
Electrical
(Voltage)
Electrical
(Voltage)
Motor
Electrical
Mechanical
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AC Generator
Similar to a DC Generator, but has no rectifier (through commutator and
brushes). [1]
Note:
To produce a sinusoidal
magnetomotive
force,
the
windings are distributed. [3]
Figure 1 Single Loop AC Generator [2]
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AC Generator Construction
In practice, it is with a stationary armature and moving field [1].
1. The armature winding is more complex than the field.
2. The armature winding can be braced more securely in a rigid frame.
3. The armature winding
protected.
(high-voltage ) can be insulated and
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Transformer
A passive electrical device that transfers electrical energy from one
circuit to another. [4]
Figure 2 Working principle of a Transformer [4]
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AC Motors
Induction Motor
Synchronous Motor
The rotor receives its power It operates at an absolutely average
inductively in exactly the same constant speed regardless of the
way as the secondary of a load.
transformer.
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AC Motor Power Flow
Where:
𝑃 - Power input
- Stator copper loss
𝑃
𝑃 - Core loss
𝑃 - Rotor power input
Figure 3 Induction motor power flow
- Rotor copper loss
𝑃
𝑃 - Mechanical loss
𝑃
- Friction and windage loss
𝑃 - Power output
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AC Motors: Single-Phase
Small motors built in a fractional-horsepower sizes, smaller than that
having a continuous rating of 1 Hp at 1,700 rpm – 1,800 rpm, and
connected to a single-phase source. [1]
Ex.
Universal Series Motor, Shaded-pole Motor, Reluctance Motor, Splitphase Motor, Repulsion Motor
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References
References
[1] Electrical Machines: Direct and Alternating Current, Charles S. Siskind
[2] AC Generator Handout - Physics 2, https://www.phys.ufl.edu/~phy3054/magnet/inductn/gens/achand/Welcome.html
[3] Magnetomotive Force And Flux Distribution On AC Machines,
https://www.theengineeringknowledge.com/magnetomotive-force-and-flux-distribution-on-ac-machines/
[4] Transformer: What is it? (Definition And Working Principle), https://www.electrical4u.com/what-is-transformerdefinition-working-principle-of-transformer/
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