Dynamic Impedance In Rotors

Improving Motor Reliability Through Static and Dynamic ... - PdMA

Crack detection by measurement of mechanical impedance of a ...

DC dynamic braking for direct determination of rotor impedance and ...

measured and predicted rotordynamic coefficients and static ...

Another fine answer from "Lynoogle.com"

We've shortened that to Noogle....

I'm afraid that this comes into the realm of "if you have to ask, you cannot do it" or (more likely) homework. We don't do homework.

A dynamic attribute is an attribute that will change as used. If you do not already have instrumentation attached to measure the impedance of the rotor of this twenty million volt ampere heater then you are just SOL.

Come on now. Cut him/her some slack. It's possible that he/she could be the director of dynamic maintenance at his/her plant. Maybe even higher. I'll bet nobody gives them any static.

Yours truly,

Lynoogle Von Noogle Esq.

I don't get any slack, why should I give it. My boss tells me to do something I know nothing about. I inform him of my ignorance. For my honesty, my schedule is moved up a week. I buy two textbooks on the subject. My nerves do fray as I work late. I meet the advanced schedule. The new engineer gets the following jobs now that I have an idea what to do. I now get a different task that's already six months late, the previous engineer for the task just quit. What is slack?

Slack is when you quit your job if somebody seriously wants you to work!

It's also how you get a train moving, one car at a time.

Before you can measure "dynamic impedance" you need to define it, providing some context and reason why you are trying to do this would also help.

I think you're referring to the transient and subtransient reactances x′ and x″ and their associated time constants τ′ and τ″, please clarify. Those terms are a function of the type of electrical machine, not the prime mover, unless you're referring to the dynamics of motion of the rotor in 3 dimensions.

Thanks for your answer. I am an electrical engineer and a costumer just made a balance in his rotor shaft and they want me to measure the "dynamic impedance", I believe to have the instruments to do it, but I prefer to be sure before sending the quote... I guess it should be somethink like: 1. move the rotor at rated speed and 2. measure voltage, current and angle... But I dont know if it is right. I've been searching information but I can't find any procedure.

I appreciate your help.

You won't find any information because it is not a common term. Since your customer wants this done after he rebalanced his rotor I believe he is referring to the mechanical, not electrical properties, of the rotor. There is a company that does certify rotors that have been machined. Unless you have equipment like this handy:

I suggest you go back to your client and ask him exactly what he expects in your report to him, and please share the answer with us.

They ask me a lot of test 1. EL CID, 2. tan delta, IR, 3. RSO, 4. diodes, 5. dynamic impedance, 6. wedges, etc. because of that I think it should be electrical. Beside they know we are electrical eng. not mechanical.Thanks for your answer and your time, we really appreciate that.

hi, I found a PEMEX document explaning the method to calculate the dynamic impedance and I share with you. You should apply 100 Vac to rotor winding, then take voltage and current measurement every 200rpm and when you find the rated speed the test will be over. Any additional information will be welcome

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Thanks, and what should the numbers look like and what do they tell you? I can only surmise that they should remain the same within certain limits otherwise the windings may have shifted. What does your document say? And what do you do if there are no slip rings, fit on a temporary pair?

Yes. Deviation more than 5% between 0 rpm to rated speed indicates that there's a inter turn problem. I paste what I find but in spanish, there's no more information...

"... aplicar una tensión constante de 100 V a las terminales del rotor, se registran los valores de voltaje y corriente en cada incremento de velocidad de 200 rpm hasta alcanzar el valor nominal. La impedancia debe permanecer constante, un cambio en el valor de impedancia significará la presencia de un corto circuitos entre vueltas. No se aceptan variaciones mayores del 5% en los valores registrados entre pasos desde 0 hasta la velocidad nominal."