Software for the Electric Machine courses

Introduction

Introduction

LabVIEW (National Instruments)

Laboratory for Electrical Machines and Power Electronics (ELMAPE)

Visualisation travelling field

Info.

Experiments

Visualisation rotating field

Info.

Step 1.  Stator: mmf and U: alternating mmf

Step 2.  V: alternating mmf and W: alternating mmf

Step 3.  Rotating mmf

Step 4.  Rotating mmf with modified supply

Further experiments


Software for the electric Machine Courses.

The LabVIEW based software for the visualisation of magnetic fields in electric machines aims at making the rather abstract origin of magnetic fields in electric machines more intuitive.

In both packages (travelling field and rotating field) it is shown that the addition of 2 or more in time varying fields (or more general: signals) which are both in time and space displaced may give rise to an in space varying field (or signal). For example, two fields with sinusoidal time variation (standing waves), which are 90 degrees shifted in both time and space, will add to form a travelling field with a sinusoidal space distribution and which moves with constant speed in space.

Visualisation travelling field: info.

Visualisation rotating field: info.

Laboratory for Electric Machines and Power Electronics (ELMAPE)

LabVIEW (National Instruments)


LabVIEW (National Instruments).

The visualisation packages (Visualisation Rotating Field and Visualisation Travelling Field) are based on the graphical programming language LabVIEW of National Instruments. Originally, this software is intended for instrumentation purposes (data acquisition, industrial automation, ...).

In this version the source code of the program (the diagram) is not included but may be requested..

For further information on National Instruments see http://www.ni.com

Introduction

Visualisation travelling field: info

Visualisation rotating field: info

Laboratory for Electric Machines and Power Electronics (ELMAPE)


The Laboratory for Electric Machines and Power Electronics (ELMAPE)

The research activities of the lab are mainly in the following fields:

•	electromagnetic field calculations: development of finite element software which uses state-of-the-art material models for the optimised design of electromagnetic devices (machines, transformers, ...)

•	noise and vibrations of electric machines and transformers

•	characterisation and modelling of electrical steels: advanced material models (e.g. Preisach type models) are developed; also, new measurement apparatus are developed for the idenification of these models

•	power electronics: various subjects are researched, e.g. active rectifiers, converters, planar power supplies for LCD’s, audio amps, passive component design,...

•	electromagnetic compatibility (EMC and EMI)

•	electrical drives: field orientation, direct torque control, dynamic behaviour of machines,

For last year students thesis works are available in each of the above subject areas.  Further information can be found on the Web page of the lab.

Introduction

Visualisation travelling field: info

Visualisation rotating field: info

LabVIEW (National Instruments)


Visualisation rotating field: Info

The LabVIEW VI “visualisation rotating field” shows the mmf distribution around the circumference of a machine resulting from a given current distribution. You may e.g. start with a 2-pole, 3-phase supply with three equal amplitudes of 0,25 and with phase angles (in both space and time) of 0º, 120º and 240º for phase Um V and W respectively.

When you open the application, the VI is started automatically; you may stop the VI using the STOP button; the VI may be restarted either

by Operate -->Run (Ctrl + R)

or by the white arrow in the toolbar

Visualisation rotating field
(Step 1: stator and U:alternating mmf)


Visualisation rotating field:

Step 1. Stator and U:alternating mmf

If but the buttons STATOR and U:alternating mmf are “ON” you will see the stator circumference (white) and the alternating mmf resulting from the supply of phase U.

Remark that the figure displays the mmf distribution, not the current distribution.

Visualisation rotating field
(Step 2: V:alternating mmf and W:alternating mmf)


Visualisation rotating field

Step 2. V:alternating mmf and W:alternating mmf

Now click the buttons V:alternating mmf and W:alternating mmf. You will observe now three alternating mmf’s along three different space axes (120° displacement) and also in time 120° displaced.

If you look at ‘the global picture’ you may observe a rotating effect (neglecting the different colours).

Visualisation rotating field:
Step 3: Rotating mmf


Visualisation rotating field:

Step 3.  Rotating mmf

By clicking the button ‘rotating mmf’ you may visualise the rotating mmf. The yellow curve shows the sum of the three single-phase mmf’s; clearly this sum has a rotational character.

Visualisation rotating field:
Step 4: Rotating mmf with different supply


Visualisation rotating field:

Step 4. Rotating mmf with different supply

Eliminate the visualisation of the three single phase mmf’s and leave only the rotating field visible.

Now we will change the supply:

•	reduce the amplitude of phase U (‘amp U’): 0,25 --> 0,15 -->0,05 --> 0; there is still a rotating effect but not at all perfect; the field consists now of the superposition of a rotating and an alternating field

•	make the three amplitudes again equal to 0,25 so that you obtain a pure rotating field. Now we change the time phase angle of phase U, e.g. 0 --> 60º. In this case as well there remains a rotating effect, but with an alternating field superposed; when you increase the phase angle of phase U to 120º or 240º the rotating component is reduced considerably but a large alternating field is left

Visualisation rotating field: further experiments


Visualisation rotating field.

Further experiments

•	change to a 4-, 6 or 8-pole configuration and explain what you see (speed, number of maxima,…).  Also you may repeat steps 1 to 4 for these multi-pole configurations (and explain!).

•	remark that for a two-phase supply the amplitude of the rotating mmf equals the amplitude of the composing alternating mmf’s; for the three phase configuration the rotating mmf amplitude equals 1.5 times the amplitude of the alternating mmf’s  (cf. the Ferraris theorem)

Introduction

Visualisation travelling field: info

Visualisation rotating field : Info

Laboratory for Electric Machines and Power Electronics (ELMAPE)

LabVIEW (National Instruments)


Visualisation travelling field

U(x,t), V(x,t) and W(x,t) are sinusoidal standing waves, i.e. both their distribution in space (the X-axis is the space axis) and their variation in time are sinusoidal. Mathematically they are of the form A·cos(k·x)· cos(l·t). Thus, an observer in a given location on the X-axis observes a sinusoidal time varying signal; when observing the variation in space at a given instant one sees a sinusoidal variation.

The three standing waves have different phase angles, both in time (angles u(t), v(t), and w(t)) and in space (angles u(x), v(x) and w(x)).

When both space and time shifts between the three signals equal 120º the addition of the three signals results in a travelling wave (i.e. mathematically of the form A·cos(k·x-l·t)).

When one or more of the phase shifts differs from 120º, the resulting signal is either the superposition of a standing wave and a travelling wave, or a pure standing wave (try it!).

The tool for the visualisation of a rotating wave is similar to that of a travelling wave; only is the space axis (X-axis) now bent in a circular shape (which may represent e.g. the stator circumference of a machine).

IntroductionVisualisation rotating field : Info

Laboratory for Electric Machines and Power Electronics (ELMAPE)

LabVIEW (National Instruments)


Visualisation travelling wave - experiments

•	When only the button U(x,t) is on (which is the default when starting the program) you will see the standing wave U(x,t) with a sinusoidal variation of the amplitude in the time domain. The X-axis in the figure is the space axis..

•	With  the buttons the standing waves V(x,t) and W(x,t) can be made visible as well. Moreover, you may change both the time and space shifts of the three standing waves (default is a symmetrical three phase system with equal amplitude and phase shifts of 120º in both space and time).

•	The button Travelling Wave allows to view the sum of the three standing waves. Depending on the phase shifts the result is either a pure travelling wave or a pure standing wave or a superposition of these..

Introduction

Visualisation Rotating Field: Info

Visualisation Travelling wave: Info

Laboratory for Electric Machines and Power Electronics (ELMAPE)

LabVIEW (National Instruments)


Info, remarks, or to obtain the source code, contact : Marc De Wulf, e-mail : mdewulf@elmape.rug.ac.be


http://elmape.rug.ac.be/elmape