Electric Motor Connections 2

[BillPall]

Hello,

I would be grateful for help solving a problem. I intend building a low impact exercise machine. It will have levers, gearbox and a generator. I have an electric motor with 8 connections all of them connect to the motor’s stator. I think it may have been part of a washing machine. The motors label information includes the term 8 µF 400 l/min. The latter seems to refer to a flow rate. After proving the electric motor will run, I intend converting it to a generator.

Please see attachment for more information, Table and diagram.

Thank you.

Regards,
Bill

 

[BillPall]

I have noticed that the attachment URL on my posting is incomplete:

http://files.engineering.com/getfile.aspx?folder=9f1bcbe7-d837-4917-ac36-78

it should be:

http://files.engineering.com/getfil...&file=Request_for_help_to_Eng-Tips_forum.docx

 

[Skogsgurra]

I am afraid that you will have quite a few problems with your venture into the electrical world. And that is for many reasons:

First, 1/min means "per minute". It indicates speed and has nothing with liquid flow rate to do.

Second, if you measure anything megohmish in a motor - just forget it. It may be your own fingers, dirt or moistness. Just about anything, except a motor winding.

Third, there is no correspondence between the W (watt) and A (ampere) numbers and any resistance you measure.

Fourth, "the term 8 uF" refers to a capacitor that is needed to run the machine. You should not try to run it without that capacitor.


So, before you have gained enough insight about motor types and electricity, I am afraid that you will either hurt yourself or start a fire if you try running that motor. This site does not encourage people to engage in potentially lethal exercises.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[BillPall]

Gunnar, thank you for your very prompt reply. I am afraid I under-sold myself. I gained two electrical qualifications, with distinctions. However that was fifty four years ago. Since then I have not needed the precise detailed interpretation I seek for the Sole motor.

l/min means litres per minute. The motor may have been used in a pumping application. However with the aid of a magnifying glass I saw that the term was 1/min. 1, l and l [one, capital i and lower case L] can be confusing. I prefer rpm. However it is not a S.I. unit.

I admit my ignorance about there being no correspondence between the W (watt) and A (ampere) numbers and any measured resistance. Please correct me if I am wrong. I understand from your statement that in this case Ohms law does not apply. This seems to imply that they are local maximum conditions that should not be exceeded. However, since the label states 1.1A 90W 900 1/min and up to 3.8A 260W 2850 1/min; that does not follow. You may be referring to impedance which would be relevant once the motor was revolving. Resistance, as you know, is impedance with zero phase angle. With my mechanical hat on, I do not have an electrical one; I am using the resistance to apply logic to determine the purpose of each terminal. I would be grateful if you would enlighten me.

I understand the need for a starting capacitor. The current leads the voltage, if I remember correctly and this gives the motor a ‘kick start’.

With regards to safety, the wording of my request makes clear that I do not intend to start the motor until I understood the circuitry.

If you able to help me understand the motor circuitry I would be pleased to receive your further replies. Even at my advanced age I am still eager to learn.
Regards,
Bill

 

[waross]

Current in an AC circuit is limited by impedance, not resistance. The impedance of a small AC motor varies over a range of about 6:1 depending on the motor speed or lack of speed.
A typical small motor may have two run windings and one start winding. It may have an internal temperature high limit switch and it may have a starting switch.
The resistance of either the starting switch or the temperature switch will be close to zero ohms. The resistance of the run winding is often different from the resistance of the starting winding (but some motors use the start winding and the run winding interchangeably depending on the direction of rotation.)
However the variations from typical are endless, particularly for small single phase multi-speed motors.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[eeprom]

If you want to build an exercise machine / generator, you should use a DC motor, which can easily be used as a generator. It will be a lot of work to do this using an induction machine.

 

[BillPall]

eeprom, thank you for an excellent reply to my query. I read it, on my mobile, while in bed at 6am yesterday morning and immediately arose and went to my computer to do some searching for DC motors. I have had some little experience of DC motors.
We, three lecturers, used to give second year students’ teams, about 5 students per team, an old computer printer and a DC servo motor, 30 watts, from which they had to make a wind turbine and generate electricity. In the second semester they were given £100 per team with which they could buy materials to modify or re-design their wind turbines. At this stage students could with other teams make joint purchases or swap components. ‘They did business’. Output was measured while the wind turbines generated power in a wind tunnel. The motors were expensive but the supplier was sympathetic. One of my colleagues created the concept.
My exercise machine will need a generator that is rated at about 200 to 300 watts. I thought a suitable DC motor would be very expensive. However, since I read your reply I have found a motor of Chinese manufacturer whose motors may not be too expensive and have sent an email requesting details. I will try to get data sheets on their DC motors.

The exercise machine will have a 3m long lever for input. When it rotates about one end it will drive the generator, via a gearbox if I have to, in order to increase generator speed. I did consider a dashpot, i.e. no generation of electricity, to create a variable resistance but a suitable one would cost about £400. I would appreciate your comments on generators. My question is how do generators perform at low speeds?
With respect to the induction motor; I did not try to run it in case I damaged it. I did insert 18 6mm diameter neodymium magnets. Hand turning achieved a voltage and a Black and Decker drill on low speed developed 27V. I could insert another 36 magnets.