Thanks electricpete for your detailed explanation. I really appreciate and, due to my poor background, I will need some time to go through your comments and digest them. I will come back soon...
Thank you very much
Thanks electricpete and GregLocock. Based on your comments, I tried to sketch the individual phase plots for Mode-1 and Mode-2 in Fig-3 (or modified as below). Let's say RED curve is the phase plot of Mode-1, BLUE curve is the phase plot of Mode-2, and GREEN is the effective phase plot. Please...
Hi GregLocock,
Thanks for your reply.
You mentioned that "... with such light symmetrical structure the mode shapes will rotate around and follow your accelerometer". I do not fully understand the underlined part. Would you please kindly advise?
I will try to increase the frequency...
Hi GregLocock,
Thanks for your reply.
In your reply, you mentioned that "... where their magnitude lines cross, they are thus equal and opposite." Can I say that because of "... and opposite", the effective magnitude, as shown in Fig-1[a] drops or "trends" to zero? By the way, how does mode-3...
Hi GregLocok,
Thanks for your reply. I have some experimental results here:
http://www.eng-tips.com/viewthread.cfm?qid=253310&page=1
I will be glad if you could comment and provide some advices to improve my coherence plots.
Thank you very much
I have an Agilent 35670A. I carried out impact hammer tests and tried to find out the resonance frequencies of a simple structure (http://www.eng-tips.com/viewthread.cfm?qid=253310&page=1). Someone replied that "...no-one uses curve fits to the Nyquist plot any more for modal analysis (because...
The following information was extracted from this article:
http://macl.caeds.eng.uml.edu/umlspace/oct03.pdf
Kindly refer to Fig-1 and Fig-2. As stated in Fig-2:
"...This is due to the fact that the magnitude of the FRF of mode 1 and mode 2 is equal at the anti-resonant frequency. But at this...
When using sound pressure level meter, does it really matter to use it with the 'ball' or without the 'ball' as shown in figure below.
Thank you very much
Hi BobM3,
Thanks for your reply. I have no access to the brush/commutator assembly. There are two pair of leads out of the motor. One of them is for field winding, whilst another pair is for armature winding. I place the 4-wire probe across the armature winding and I find out the measurement is...
Hi Dr MikeyP,
Thanks for your advices. My background is electrical engineering and therefore I do not have much knowledge regarding modal analysis. I really hope that you will help and guide me to clear my doubts on impact hammer test.
You mentioned that "... there are probably 5 modes"...
I carried out impact hammer test on a motor end cap as shown in Figure 1. The hammer has a built-in force sensor. Hammer hits were repeatedly applied at around 'X' location. The vibration response was measured by an accelerometer (blue). The output of the hammer force sensor and the output of...
I've a brushed DC shunt wound machine with the following specs:
Rated Speed: 3000rpm
Rated Power: 0.25kW
Armature Voltage: 180V
Armature Current (full load): 1.6A
Field Voltage: 210V
Field Current (full load): 0.2A
I did some calculation as follows:
w = n*2*pi/60 = 3000*2*pi/60 = 314.1593 rad/s...
Hi DickDV, thanks again for your suggestion. Unfortunately, we have not purchased the DC machine yet. Due to limited budget, we wish to make sure that we will buy the right DC machine that will suit our application before we purchase.
The "K" in my calculation is EMF constant, which is equal to...
What does "base speed = 1750rpm" mean? Does it mean the speed at FULL LOAD (i.e. at Ia = 11A) is 1750rpm?
I just received the torque-speed curve from Baldor, which shows that at FULL LOAD, the speed is around 1610rpm. Which one is correct?