Electric Motors in the Home Workshop parts 1&2

[9fingers]

Well folks here is the first part as a draft which aims to show the basic of induction motors both single and 3 phase.

There is also a list of proposed future topics on the last page which will no doubt get added to. It has made me realise just what I've taken on!

Please feel free to comment good or bad!

http://homepage.ntlworld.com/bob.minchi ... aft0.1.pdf

Enjoy!

Bob

 

[Boz62]

Excellent. Just the right level for me .

Keep up the the good work

Boz

 

[chill]

Brilliant, thanks very much Bob, just what I need.

 

[CHJ]

Yet another good forum resorce in the making Bob.

(By the time you have completed the basic guide to 1-3ph power convertors and all the permutations of with/without braking you will deserve a bacon butty at the next gathering :lol: :twisted: )

 

[Niki]

Hi Bob

Excellent....and now I know why my router and hand held circular saw are so noisy....

On table 1, you made a conversion of kW to hp...I think that it's better to emphasize that you are talking about the "Output Power" and not the "Input power" that is stated on the name-plate or as you call it "rating plate".

Not many makers will give you the output power...well, we want to sell - don't we

On the pic below, you can see my motor Input power and Output power (what they call Motor Capacity) of my EB PK255.
The output power is only 1.9 kW that are only ~2.5HP ......If you just could explain to me please what is the "S6 40%"...

A small story from the American marketing method...They have a shop-vac for $50 and "6.5 pic HP" ....I replied to the guy "Buy it quickly and change the motor on your table saw"...of course looking at the spec it shows 11A motor...

Thanks
niki

 

[9fingers]

Hi Niki,

Thanks for your comments.

I had to look this one up!!

S6 40% refers to the duty cycle that the motor can deliver that power.

Where no time period is stated, 10 minutes is assumed.

So your motor will deliver that power for 4 minutes (40% of 10 minutes) and then need 6 minutes rest (to cool etc) before being able to work again at full output for another 4 minutes and so on.

I am not sure but I think the motor has to be running for the rest period but unloaded to take advantage of the cooling fan.

There is some more info here http://www.entrepreneur.com/tradejourna ... 10994.html.

HTH

Bob

 

[cutting42]

Please feel free to comment good or bad!

Hi Bob

Speaking as a very lapsed IEE member and someone who was more on the electronics side of things, your notes brought memories of lectures flooding back!

A nicely written guide and will be a great reference document.

 

[9fingers]

Please feel free to comment good or bad!

Hi Bob

Speaking as a very lapsed IEE member and someone who was more on the electronics side of things, your notes brought memories of lectures flooding back!

A nicely written guide and will be a great reference document.

OOH! I had rather hoped they would be more use than my lecture notes were when it came to reality :shock:

In my student days (70s) I recall feeling "ok that was the lecture but what does that mean in practise?"

Bob

 

[cutting42]

OOH! I had rather hoped they would be more use than my lecture notes were when it came to reality :shock:

Oh they are way better than my lecture notes which I tried to review a few years ago but could not even read the writing, let alone understand what I had written.

 

[Niki]

Thank you so much for your clarification

Regards
niki

 

[Nigel]

Hi Bob
here is another old electrician who used to wire up motors on a daily basis for my living, the clarity of your writing is great and brought back many memories including "ringing out a motors terminals " when they came back from a rewind without any markings on the terminals,
I have been away from front line wiring for so long now I am reluctant to advise anyone on motors for fear of forgetting something critical so more power to your elbow and look forward to future editions,

Cheers Nigel

 

[9fingers]

Thanks Nigel,

Good to hear from you. It has been a while since we met last at Barry B's house.
Hope all is well with you.

Best Regards

Bob

 

[SammyQ]

Bob, "THANK YOU!" The file so far has been simple, well illustrated and informative. As my teenage son would say: " Go on, my son!"

Sam

 

[9fingers]

Part two is now in draft form here

http://homepage.ntlworld.com/bob.minchi ... aft0.2.pdf

I'm not sure I can keep this rate of progress up. SWMBO has been making comments about having my nose in my laptop all day as well as all evening!!

They just don't understand sometimes :lol:

Happy reading and comments welcome


Bob

 

[Gower]

Thanks for a very informative and easy to follow article. Your hard work is much appreciated even if your wife isn't so keen!
Cheers,
Jim

 

[Boz62]

I'm impressed with your work rate :shock:. Still spot on.

Boz

 

[9fingers]

I'm impressed with your work rate :shock:. Still spot on.

Boz

Its one of the advantages of not working for a living. I can start something and just plug away at it. Until something else take priority that is!

Bob

 

[RobertMP]

Couple of typos but good stuff

I did all this stuff back in the 70's too (ONC electrical engineering). Surprised how much I remember. Star Delta starters/ simple contactors worth a mention as they often come with larger 3 phase motor machines?

 

[9fingers]

Hi Robert,

I found 1 typo on page 1 (know instead of known)

please could you point out the other(s).

I had wondered about star/delta starter but so have rejected covering them as I had reckoned on them being pretty rare in a home workshop situation.
Also bearing in mind that this is leading up to a main section on running 3 phase kit from single phase, inverters will soft start motors so the need to star/delta largely goes away.

I'll make a bit more reference to it in the next issue.

Cheers

Bob

 

[Tony M]

This is a timely subject. I disassembled my bandsaw a few years ago and foolishly didn't make note of where the yellow wire from the single phase motor attached to plug wiring box thing. Perhaps a photo of my dilemma would be more explanatory. If i knew how to insert a photo that is :? [/img]