Laminated Core of Motor

Epoxy or mica can be used. They will not be spot welded due to the problem of eddy currents.

Further to that point, if rivets are used, aren't they brass or copper or some nonmagnetic material?

Laminated Core is made up of:

Cold Rolled Grain Oriented (CRGO) Sheet Steel in case of Transformers

and

Cold Rolled Non-Grain Oriented Steel (CRNGO) Sheet Steel in case of Motors Generators

I enjoyed your answer, here's a GA from me. It'd be great if sometime you could revisit your old plant (hopefully it's still in operation), and take some photos. With your experience, you'll remember the right things to photograph, and the right issues to illustrate.

I used to work on a large appliances company, they manufacture small eletric motor at very high volumes. The stacked sheets for stator are welded and the slots protected insulated with plastic foil, then the wire are inserted. You can see this kind of equipments at http://www.statomat.com.br/.

For rotor the stack ar pressed on a mandrel and goes inside a aluminiun injection mold, there the wiring are made in one shot.

Very interesting.

I note the weld bead is on the outside of the stator and leaves an "open" electrical path for eddy currents.

On the production welding are they using mig or tig and a robot?

High volume small motors need all the cost savings possible. On large AC a man day one way or the other is hardly noticed! (example +/- $500 on a $200k motor). Quality is paramount however, in that the cost of a "shipped" defect is devastating).

In my line of work, which is submersible pumps, Baker Hughes, manufacture their motor with encapsulated windings. They make the motor stator as described and then using a process only known to themselves, they cover the windings in a black resin which sets. Numerous reasons why they do this, one, being the patent, two, they say it improves heat convection (the jury is still out on that point).

The downside is once the motor has burnt, and submersible pump motors do burn with alarming regularity, the whole of the stator is scrapped. The rotors, bearings & other items of the motor can be re-cycled, but the housing (which can be 20 foot plus long),windings and laminates cannot be recovered.

In support to the replies, now a days torque motors from FANUC & others companies also encapsulting with epoxy resins to Stator...

my idea about this is to remove heat and giving high conductivity to stator flux...

&

Thanks GW,

According to you, insulation presents between 2 metal sheet(stampings),

If so, when eddy currents induces it may lead to formation of capacitance, correct...

If i am wrong in above two ideas, please correct me...

With regards,

The encapsulation is usually for electrical insulation purposes, especially with the use of VFD drives the insulation is stressed much higher. It is certainly a bonus for chemically hostile or wet locations.

The rotor and stator are designed with ventilation slots and air flow circulation, even in TENV motors where it is air circulation within the enclosure.

The new insulation systems can withstand much higher temperatures and it is quite common for class F or H insulation systems.

The iron core supports the magnetic flux. The winding creates the flux. The insulation system (including between the laminations) supports neither current or magnetic flux.

The winding insulation prevents the iron from becoming energized with current.

The laminations with its very thin insulation reduces eddy current losses that shows as heat losses in the core,

Any capacitance effects are parasitic, not wanted, and a nuisance, and sometimes contributes to premature bearing failure.

Hi

Is there any difference in manufacturing of transformer, Motor & generator core..???

With regards,

Yes!

Dear friends,

Suggest me some links or good books which explains me the manufacturing process of Motor and generator....

With regards,

do you not have google? Thats where most people would go to provide you with the sites you require!

Slemon and Straughen - Electromechanical Systems

Kraus and Carver - Electromagnetics

Go visit a local rewind shop. There are usually a half dozen or so in mid size city.

The transformer core is constructed from thin laminations of silicon steel sheets. That small sheet is laminated to create the center of the transformer and then all sheets are alleviated in certain ways.

Such thin sheets are used to the currents of eddy. As the sheets are very thin and laminated too,..... eddy currents are reduced to extremely low levels and the losses decreased, increasing the efficiency of the transformer.