TWO SPEED DAHLANDER MOTOR 1

[petronila]

Dear All,

Some machines like Lifting cranes are equipped with Two Speed Motors-Dahlander connection.

In this case is an electric motor Constant torque, 2.8/1.4 HP, 1420/700 RPM, 50 Hz, 220 Volts, the core is in cone shape for it you have a biggest and smaller core diameter and a biggest and smaller back iron . How calculate this winding?? any formula ?

Thanks in advance for your help.

Petronila

 

[aolalde]

Hello Petronila.

I wish it should be a formula; it is a little more complicated. My only advise; go to EASA website

http://www.easa.com/

and buy the following program:

The "AC Motor Verification & Redesign Program" on CD-ROM is everything you expect from an easy-to-use Windows-based program. This program lends itself to easy verification of either concentric or lap windings, as well as redesigns with changes in poles, horsepower, or voltage. The redesign printout is in the EASA data sheet format, with the original and new data printed out on the same page for convenience. All entered data can be automatically saved in order to build your own database of customer winding data. Other features of the program include:
• Rectangular wire input, as well as AWG or metric are accepted.
• The user default settings can be established when you start using the program, letting you select AWG or metric for the redesign wire size.
• The redesign gives you the wire size, not just a circular mil total. Version 2.0 is Windows® 2000 compatible. It also features other enhancements, such as allowing redesign from single-speed to two-speed single-winding.
AC Motor Verification & Redesign Program on CD-ROM Version 2.0

AC Motor Verification & Redesign Program on CD-ROM Version 2.0 Upgrade

Good luck.

 

[petronila]

Aolalde, Thanks for your comments,

Yes you are right, We know about this program, but in this case is an special motor due to the Core diameter and the back iron have diferent sizes in each end bell, one smaller and other biggest.

I was made a calculation using each two sizes average, and the motor was rewound,but the motor is drawning too much no load current, I think the problem is mechanical and will be necessary a better air gap calibration The airgap, with the rotor pulled into position, is normally between 0.35 mm and .46 mm I can assemble it without the spring, and use feeler guages to measure the airgap. or a large C-clamp can be used to compress the spring.

Thanks again.

Petronila

 

[aolalde]

For those motors with conical bore you have to use average dimensions for the diameters and back iron. However, as far as I know, the air gap has even spacing since both stator bore and rotor outside diameter have the very same taper ratio.

The reluctance should be calculated for the air-gap when the operating condition is reached (spring compressed). In theory the core length for the stator and rotor align axially when the winding is energized, if not you are loosing lamination and the magnetic circuit densities will increase resulting in high magnetizing current.

 

[petronila]

Thanks again, aolalde,
You are right again.

Regards

Petronila