DC Motor

Yes students do need labs with big machines and yes they do leave an indelible impression .

Many years ago I was in a lab group that shut down the whole Physics school of a large college 3 times doing an experiment with a big machine where a careless technician (not a student) had reversed the wiring of a Synchroscope. but the lab was designed and built by experienced engineers and so no-one was hurt. The OP in this thread is asking questions that are obviously beyond his current (sic) level of expertise and this is not the place to learn that sort of stuff. He will get bits and pieces of advice and never know till after the fire that he didn't ask all the relevant questions and so did not get all the answers.

Hi Thank you all I agree with after reading all the messages that i really did not think of all the measures and questions. Could some body educate me what more i need to know. before testing I think i need to prepare a test plan/procedure and what all will i calculate and how i will show my demonstration. If they agree my experience with dealing large machines is not sufficient atleast they would see my test plan and do the test with some expeerienced. Hope i get some help and appreciate all for the info provided. Regards smitha

Heh, heh. A man after my own heart!!

I'm currently devel> >

Smitha

Would it be OK for me to ask what kind of school you are attending?? It is difficult to consider that there is a school that would present you with a 25 HP DC motor without first acquainting you with the the fundamentals.

Perhaps English isnt your first language.

When you ask this News Group to educate you, it seems that you have no instructions available from that school.

I's suspecting this is a prank post. How about you supply a little more background on what you are doing and maybe where you are.

Jerry

bricks

toward

Have to agree-the only computer simulation I ever did was a second order system patch wired on a General Dynamics analog computer. Everything else was lab work...

As you have seen from the replies, there's various ways to determine motor constants.You need to tell everyone what you DO know about DC motors first. Are you familiar with the basic DC motor equations? What are the capabilities of the lab-any equipment to measure large torques and currents?

The electrical and mechanical input/output levels you will be dealing with can be lethal. If this is for a school lab project I'd suggest you consider a 12 volt permanent magnet motor from a car (engine cooling fan or blower motor) and determine the motor constants.

I'd put something like 100V across the field winding and see what the output is for the armature when turned at a speed near the rated speed. The thing that is nice about DC motors is that the can be used easily as DC generators, especially if the field is a magnet. The other thing about DC motors is that they will spin on much lower voltages (10^ os rated voltage is a good starting point for low speed operation) although the current will be the same approximate valuee as the full speed current. Currrent, of course, goes up with load from some value which may be 50% of the max current.

-- Why do penguins walk so far to get to their nesting grounds?

Respect and perspective. Ya can't get into much trouble with a 1 HP motor. Wiring a 24-volt doorbell is not sufficient preparation for working wtih 440V wiring, though the same theory applies to both.

you can... meat grinders have 300 watt motors...

Surely I see your point. Physics is about the same, but emotional impact of a large motor can have some extra educational value.

i

In all actuality this might be a drill press from Sears. You know "Maximum Developed HP" crap they label everything with.

Sears has really turned into a joke. Everyday I am on edge that they will go out of business and my hand tools will be about worthless. Should I just start buying the Chinese crap now?

I actually took a glance at a drill press at Sears. Looked at the back to find the plate on the motor in an attempt to find the true HP. Conveniently the plate was missing, but the 4 rivet holes where there. Nothing more insulting.

NNTP-Posting-Host: 12.2.142.7

resolves to:

Caterpillar, Inc. CATERPILLAR-142-0 (NET-12-2-142-0-1) 12.2.142.0 - 12.2.142.255

Bingo. Troll

Gunner

The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty." Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly save yourself, but it is too late to save that society. It is doomed. " Lazarus Long

I would start by making sure that sucker was very securely anchored to something fairly bit -- you set something like that on a "bench" or anywhere else for that matter and apply power it will do 2 things:

1) take off in a hurry in some direction from the torque and 2) either rip your wires out or just twist them together for lots of fireworks (and 25 Hp is capable of taking a small "bench" with it when it starts).

mikey

Yep. I recently bought two single phase motors, 2 and 5 HP, and they would have jumped off the table if I was not holding them tight with my hand.

i