Motor load inertia 3

[rockman7892]

I have been searching but have been unsucessful in finding out how a load inerita relates to a certain motor hp.

For instance if I have a 300hp 4160V motor is there a table of formula that relates this hp to the maxiumum load inertia that this motor can handle?

I have a motor that I am RVAT starting and am seeing high starting current which are actually much greater than the LRC at 80%V. I was wondering if a higher load inertia could drive these current high enough that the motor would still start but yeild a higher LRC at less voltage.

The motor is a 300hp motor and the load ineria from the load manufacturer is 27090 lb/ft^2

 

[EddyWirbelstrom]

The zipped ptw project file and the excel spreadsheet weres not attached, I'll try again.

 

[EddyWirbelstrom]

It seems I can only send one file at a time, the attached file is the excel spreadsheet with motor and load data used to build the PTW TMS motor and load library. All load torque and inertia was referred to the motor.

 

[EddyWirbelstrom]

I've attached plots of the TMS study showing accel time of 9.5 sec.
The plots are very similar to those of LionelHutz.

 

[rockman7892]

mnewman

I apoligize, I did not have access to a computer last night and was not able to answer your questions.

The version of SKM that I am using is version 6.0 3.5 b7. I am not able to open your project file so this may be the reason if you are using version 6.5.

It looks like you found the necessary information to answer the cable impedance question.

In regards to your question involving confirming the load speed vs toruqe curve, this looks correct to me and this is indeed what the manufacturer has given me.

I really appreciate your efforts and your help with plotting and figuring out this motor starting analysis. I just got in the office and am going to go through what you have posted and try to understand it completely so I have a complete understanding when discussing results.

Thanks soo much again for your help and efforts.

 

[LionelHutz]

Nice results mnewman.

Too bad SKM doesn't internally handle the different units - will it handle the speed reducer internally? I wrote the program I used to handle the units that are given (and any speed reducer) making it's use pretty easy.

But then, SKM will model the system better so as with everything it's a trade off.

 

[EddyWirbelstrom]

Rockman7892 and LionelHutz
On page 8 of the attached file I have added the TMS plots for an 80% autotransformer tap which switches to 100% 14 sec after motor start for an increased start time of 14.6 sec.
PTW can be set for either FPS or MKS units, I had not done a TMS in FPS before and was unsure of FPS units for inertia.
PTW can also plot the motor hot and cold withstand curves against the TMS motor starting current.