Re: [Emc-users] 1.5 kw vfd in 6040 problems

[Jon E. <el...@pi...>]

On Thursday 24 January 2019 08:41:47 Todd Zuercher wrote:
>> I have a fair amount of experience with high speed spindles.  And I've
>> found that most are incapable of running much below about 1/3 of their
>> rated speed for any length of time, and cutting anything at those
>> speeds is certainly out of the question.  If you don't believe me,
>> start your 18k rpm spindle at 4000rpm and then check the current
>> readout display on the VFD, and you will be shocked at what numbers
>> you see displayed (I'd venture a guess that it would be close to about
>> 200% of rated amps on the motor name plate).
>>
This would indicate the Volts/Hz ratio is not set right.  
This might make the spindle accelerate better, but if set up 
properly, you should not see excessive current at low 
speeds.  Some drives have multiple breakpoints, so the V/Hz 
curve can have multiple slopes between those points.

We have a really off-brand mill at work that has an 18000 
RPM spindle.  You can run it all day at 1000 RPM with no 
heating.  It really lacks torque at all speeds, obviously 
designed for high speed, but won't burn anything up.

Jon