Motor current ratings when using Variable Frequency Drive (VFD)
Motor current ratings when using Variable Frequency Drive (VFD)
(OP)
Dear Sirs,
I am having a little bit of difficulty understanding the datasheet, which is attached, for a 315kW BROOK Crompton Motor. Specifically, I could use some help understanding the significance of the current values. Is the 526.2 Amps (labeled Amps Ia @ 400V) the locked rotor current?
Is the 127 Amps (labeled N.L. Amps) the current draw at full load torque.?
If one was to use a Variable Frequency Drive(VFD) at which current level would one need to rate the Drive (and associated cabling)? Presumably, with the VFD one will not be drawing the full locked rotor current during start-up.
The motor is for use with a wood chipper. Would it be more common to use a soft starter than a VFD in such an application?
Any advice would be much appreciated. Thanks, Folks!
I am having a little bit of difficulty understanding the datasheet, which is attached, for a 315kW BROOK Crompton Motor. Specifically, I could use some help understanding the significance of the current values. Is the 526.2 Amps (labeled Amps Ia @ 400V) the locked rotor current?
Is the 127 Amps (labeled N.L. Amps) the current draw at full load torque.?
If one was to use a Variable Frequency Drive(VFD) at which current level would one need to rate the Drive (and associated cabling)? Presumably, with the VFD one will not be drawing the full locked rotor current during start-up.
The motor is for use with a wood chipper. Would it be more common to use a soft starter than a VFD in such an application?
Any advice would be much appreciated. Thanks, Folks!





RE: Motor current ratings when using Variable Frequency Drive (VFD)
RE: Motor current ratings when using Variable Frequency Drive (VFD)
RE: Motor current ratings when using Variable Frequency Drive (VFD)
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Motor current ratings when using Variable Frequency Drive (VFD)
Soft Starter + Bypass is the time honored and accepted way of accelerating a chipper. Buy a good quality soft starter, tell your supplier what you are using it for and have them acknowledge that they understand. You do NOT want the cheapest soft starter you can buy for this.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
RE: Motor current ratings when using Variable Frequency Drive (VFD)
A VFD that size will require a lot of airflow for cooling which means fans, and it's not hard to guess how quickly the fan filters will clog in that environment.
RE: Motor current ratings when using Variable Frequency Drive (VFD)
Thank you for the responses. djs is it definitely the 526 Amps that should be used for sizing the VFD. Surely it will not draw anywhere near this if the startup is controlled.
Thanks ALL
RE: Motor current ratings when using Variable Frequency Drive (VFD)
RE: Motor current ratings when using Variable Frequency Drive (VFD)
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
RE: Motor current ratings when using Variable Frequency Drive (VFD)
RE: Motor current ratings when using Variable Frequency Drive (VFD)
The lowest I have seen was 150% FLA current starting a bow thruster.
RE: Motor current ratings when using Variable Frequency Drive (VFD)
RE: Motor current ratings when using Variable Frequency Drive (VFD)
May be the soft starter will not operate on full load at first of installation.
RE: Motor current ratings when using Variable Frequency Drive (VFD)
One more question on this. Could someone clarify for me the meaning of LRC(DOL) and LRC(SD) on the attached Brook Crompton motor datasheet? I think LRC(DOL) is Locked Rotor Current direct online. I am not sure of the other. An explanation would be appreciated. What is the difference between the two?
Many Thanks
RE: Motor current ratings when using Variable Frequency Drive (VFD)
Bill
--------------------
"Why not the best?"
Jimmy Carter