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Manufacturing Effects on Iron Losses in Electrical Machines
KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In this master thesis, the magnetic properties of SiFe laminations after cutting and welding

are studied. The permeability and the iron loss density are investigated since they are

critical characteristics for the performance of electrical machines. The magnetic measurements

are conducted on an Epstein frame for sinusoidal variations of the magnetic ux

density at frequencies of 50, 100 and 200 Hz, according to IEC 404-2. Mechanical cutting

with guillotine and cutting by means of ber and CO2 laser are performed. The inuence

of the ber laser settings is also investigated. Especially the assisting gas pressure and

the power, speed and frequency of the laser beam are considered.

In order to increase the cutting e ect, the specimens include Epstein strips with 1,

2 and 3 additional cutting edges along their length. It is found that mechanical cutting

degrades the magnetic properties of the material less than laser cutting. For 1.8% Si

laminations, mechanical cutting causes up to 35% higher iron loss density and 63% lower

permeability, compared to standard Epstein strips (30 mm wide). The corresponding

degradation for laser cut laminations is 65% iron loss density increase and 65% permeability

drop. Material of lower thickness but with the same Si-content shows lower

magnetic deterioration. Additionally, laser cutting with high-power/high-speed characteristics

leads to the best magnetic characteristics among 15 laser settings. High speed

settings have positive impact on productivity, since the cutting time decreases.

The inuence of welding is investigated by means of Epstein measurements. The test

specimens include strips with 1, 3, 5 and 10 welding points. Experiments show an iron

loss increase up to 50% with a corresponding 62% reduction in the permeability.

A model that incorporates the cutting e ect is developed and implemented in a FEMbased

motor design software. Simulations are made for a reference induction motor.

The results indicate a 30% increase in the iron losses compared to a model that does

not consider the cutting e ect. In case of laser cut core laminations, this increase reaches

50%. The degradation prole considers also the deteriorated magnetizing properties. This

leads to increased nominal current up to 1.7% for mechanically cut laminations and 3.4%

for laser cut la

Abstract [sv]

I detta examensarbete studeras hur de magnetiska egenskaperna hos SiFe-plat paverkas

av skarning och svetsning. Permeabilitet och jarnforlustdensitet undersoks eftersom de

ar kritiska variabler for elektriska maskiners prestanda. De magnetiska matningarna

genomfordes pa en Epstein ram med en odesfrekvens pa 50, 100 och 200 Hz, enligt

IEC 404-2. E ekterna av mekanisk skarning med giljotin samt skarning med ber- och

CO2-laser studerades. Inverkan av olika berlaserinstallningar undersoktes ocksa genom

att variera gastrycket, skarhastigheten samt frekvensen och e ekten av laserstralen.

For att oka skare ekten inkluderades Epsteinremsor med ytterligare 1, 2 och 3 langsgaende

skarsnitt. Det visas att mekanisk skarning har en mindre paverkan pa de magnetiska

egenskaperna hos materialet an vad laserskarning har. Matningar pa plat med 1.8% Si

visar att da prov med tre extra langsgaende giljotinklipp anvands kan permeabiliteten

reduceras med upp till 63% och jarnforlusterna kan oka med upp till 35%. Motsvarande

resultat for laserskurna platar visar en permeabilitetsreduktion pa upp till 65% och

en jarnforlustokning pa upp till 65%. Ur studien av de tva studerade skarprocesserna

framkommer aven att tunnare plat paverkas mindre negativt an tjockare plat. Ett antal

olika installningar har provats for att utreda hur olika parametrar paverkar e ekterna

av laserskarning. Studien indikerar att skarning med hog e ekt och hog hastighet ger

den minsta paverkan pa materialets magnetiska egenskaper. Vilket aven har en positiv

inverkan pa produktiviteten vid laserskarning.

Epsteinprover har aven utforts for att undersoka vilka e ekter som introduceras da

SiFe-plat svetsas. Provstyckena bestod av remsor med en, tre, fem och 10 svetspunkter.

Experimenten visar en jarnforlustokning med upp till 50% samt en permeabilitetsreduktion

upp till 62% da platarna svetsats samman tva och tva.

En modell for att studera e ekterna av de forandrade materialegenskaperna vid skarning

pa en induktionsmotor utvecklas och implementeras i en FEM-baserad mjukvara. Resultaten

tyder pa en jarnforlustokning med 30% da skare ekten orsakad av giljotin beaktas.

Vid simulering av laserskuren plat kan denna okning vara sa stor som 50%. Det framkommer

aven att laserskarningen kan reducera e ektfaktorn sa mycket som 2.6%.

Place, publisher, year, edition, pages
2015. , 104 p.
Series
EES Examensarbete / Master Thesis, XR-EE-E2C 2015:006
Keyword [en]
electrical machine, induction motor, iron losses, relative permeability, guillotine, ber laser, CO2 laser, laser settings, cutting effect, welding, electrical steel.
Keyword [sv]
elektrisk maskin, induktion motor, järnförluster, relativ permeabilitet, giljotin, fiberlaser, CO2-laser, laser inställningar, skäreffekt, svetsning, elektromagnetisk plåt
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-172373OAI: oai:DiVA.org:kth-172373DiVA: diva2:847378
External cooperation
ABB Motors
Educational program
Master of Science - Electric Power Engineering
Examiners
Available from: 2015-08-20 Created: 2015-08-20 Last updated: 2015-08-20Bibliographically approved

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