KD5067 Assignment
Faculty of Engineering and Environment
BENG (HONS) ELECTRICAL AND ELECTRONIC ENGINEERING
Module title: Power, Machines and Renewable Energy
Assignment: 3-phase Induction Machine Performance
Student Name:
ID:
Bench:
Submission date:
102-27-2023 11:14:44 GMT -06:00
This study source was downloaded by 100000861498583 from CourseHero.com on
https://www.coursehero.com/file/133235337/3-phase-Induction-Machine-Performancepdf/
KD5067 Assignment
Requirements
•
•
•
Students need to attend one laboratory session, as per the group timetable,
where they will be given all the necessary instructions on the machine testing
procedures required to take the relevant measurements.
Prepare a brief report (preferably Word edited) to include explicit responses to the
questions below, and submit it to the module ELP by 28 April 2022. Please use
this Word file as a template adding the required number of answer sheets as
appropriate. Make sure you complete the sections on the cover page above (e.g.
name, ID, your bench number when you did your lab session, as well as the
submission date).
In case of late submission without a proven good cause, your assignment will
incur fail or zero mark. In the event that you submit the assignment late but with
a genuine reason, you must complete a late submission form available from the
Student Central, and then have it authorised/signed by the module tutor.
Content
Induction machines are the main work force in industry today and about 75% of the
installations are based on them one way or another, either in motoring or generating
mode. Although it is possible to achieve variable speed operation using power
electronics, many general-purpose drives or fixed speed wind turbines require a fixed
voltage and frequency supply for the machine. In these systems, 3-phase induction
machines are indispensable due to their unique self-starting ability and possibility of
direct on-line operation unlike any other 3-phase AC machine. This inherent property
represents a significant advantage over its counterparts, and it is mainly for this reason
that they are difficult to beat on the market in a wide range of applications. The proper
understanding of the machine fundamental operating characteristics and testing
methods used in practice is therefore of utmost importance, especially if the students
wish to continue their further professional career in power engineering companies,
electric machines and drives industry or renewable energy sector (e.g. wind turbine
manufacturers). The main objective of this assignment is to allow the students to gain
the necessary practical experience and basic knowledge in this area.
The experimental test rig, procedures and equipment used for testing of a
smallscale cage induction motor, have been described in the accompanying laboratory
sheets, hard copies of which you should have already received in the lab sessions.
202-27-2023 11:14:44 GMT -06:00
This study source was downloaded by 100000861498583 from CourseHero.com on
https://www.coursehero.com/file/133235337/3-phase-Induction-Machine-Performancepdf/
KD5067 Assignment
Tasks
1. From your test results, determine the machine synchronous speed and the number
of poles.
[6 %]
2. The example cage induction machine was started using a variable voltage supply
at 50 Hz.
a. What is the main reason for adopting such a starting procedure as opposed
to dead-on-line start, and especially with larger machines?
[3 %]
b. State alternative electro-mechanical and power electronics starters (at least
one configuration for each) which can be used for the same purpose. What
are the main advantages of the latter over the former?
[4 %]
c. Identify the common problem of fixed frequency operation with respect to the
starting torque and current of the motor?
[3 %]
3. If the same 400 V, Y-connected machine was Δ-connected (as you did in your
experiments), what maximum voltage could be applied to its terminals to prevent
the current over-loading? Compare (in relative sense) the line current and torque
values for the two winding connections of the motor for a given speed?
[7 %]
4. Using the table on page 8 of the laboratory sheets as a template, tabulate the
measurements taken for the line current, 3-phase electrical power, power factor,
load torque (note: the measured values may necessarily differ from those provided
in the table referenced above), speed, calculated slip in motoring mode, and speed
and electro-magnetic power predictions for the machine operated as a generator at
the same absolute slip and shaft torque values as for the motoring operation.
[30 %]
5. Using Excel spreadsheets or similar software available for this purpose, present
graphically the following operating characteristics of the motor in terms of torque:
speed, current, power factor, input power and slip (two plots per figure for each, one
for Y and one for Δ connection for straight comparisons).
[30 %]
6. Using the approximate equivalent circuit, show that the machine electro-magnetic
torque is proportional to slip in the low slip region, and verify this linear relationship
by the corresponding experimental plot(s) above.
302-27-2023 11:14:44 GMT -06:00
This study source was downloaded by 100000861498583 from CourseHero.com on
https://www.coursehero.com/file/133235337/3-phase-Induction-Machine-Performancepdf/
KD5067 Assignment
[7 %]
7. In your experiments, 3-phase power has been measured by means of two single
phase watt-meters connected as illustrated in Fig. 4 of the lab sheets (this is known
as the ‘two-wattmeter method’ in the literature). Using phasor diagrams, an
expression for instantaneous power, or applying any other approach you consider
appropriate, explain how is this possible and why?
[10 %]
402-27-2023 11:14:44 GMT -06:00
This study source was downloaded by 100000861498583 from CourseHero.com on
https://www.coursehero.com/file/133235337/3-phase-Induction-Machine-Performancepdf/
Powered by TCPDF (www.tcpdf.org)