Re: [CAD_CAM_EDM_DRO] Motor calculations? Help!

snaketracks wrote:

>
>What calculations could I use to figure out the max voltage and
>current specs on these motors? I am trying to figure out what
>voltage to make the power supply and which drivers to get. I want to
>have enough supply to run the motors up to the max rating of 2000
>RPM, so I think the power supply has to be somewhere above 50V for
>the Z axis motor and above 100 Volts for the X and Y going by the
>back EMF that has to be overcome. I just don't know how much higher
>or how to calculate it. Or I could even be way off base. Any help is
>much appreciated. Please e-mail me at jevs@... if you have
>any ideas. Here are the only motor specs, I had to pester Fanuc with
>about 10 phone calls before they would even give me this. They are a
>pain to get info from:
>
>Fanuc DC Motor 0 (z axis)
>Type: 0-2000M
>Output Power: 0.4 KW (0.5 HP)
>Rated Torque: 28 Kg-Cm
>Max. Torque: 240 Kg-Cm
>Max. Speed: 2000 Rpm
>Rotor Inertia: 0.029 Kg-Cm-S 3
>Back EMF Constant: 25 V/K RPM
>Torque Constant: 2.44 Kg-Cm/Amp
>Mechanical Time Constant: 25 mSec
>Thermal Time Constant: 50 Min
>Weight: 12 Kg
>
>

2000 RPM needs 50 V plus an allowance for I*R drop. I don't see a
figure for armature resistance,
so I can't calculate farther on that. at 2.44 Kg-Cm/Amp, and 240 Kg-Cm
peak, the peak current is
98 Amps!

>Fanuc DC Motor 5 (x,y axis)
>Type: 0-2000M
>Output Power: 0.8 KW (1 HP)
>Rated Torque: 55 Kg-Cm
>Max. Torque: 480 Kg-Cm
>Max. Speed: 2000 Rpm
>Rotor Inertia: 0.05 Kg-Cm-S 3
>Back EMF Constant: 50 V/K RPM
>Torque Constant: 4.87 Kg-Cm/Amp
>
>

50 V/KRPM * 2 (000) = 100 V + I*R. I peak is 98.5 A. I'd think a 150 V
supply would be
good here. Hmm, I assume you will be retrofitting a Kearney & Trecker
horizontal boring
mill or similar monster machine with motors like this! These X-Y motors
could crank a
large V-8 engine with no direct drive to the crankshaft! Do you really
need to hang a 16 Kg
motor on your axes? Can your leadscrews and structure withstand such a
motor?

Jon