Fanuc DC Motor 0
Type: 0-2500M 2500 pulse encoder
Permanent Magnet DC Servo Motor
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
Fanuc DC Motor 5
Type: 0-2500M 2500 pulse encoder
Permanent Magnet DC Servo Motor
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
Mechanical Time Constant: 15 mSec
Thermal Time Constant: 55 Min
This is some notes I made when I was looking for similar information and found them in various sources:
equations are:
1. V=Ia R + Ke omega (Ia=armature current, R=armature resistence,
Ke=electr. constant, omega=speed)
2. Tg=Kt Ia (Tg=costant, Kt=torque constant)
3. Tg=J d(omega)/dt (J=inertia, d(omega)/dt=accel.)
The DC motor transfer function is:
Gm(s)=(1/Ke)/(1+s(Rj/KtKe)), which can be written Gm(s)=(1/Ke)/(1+sTm)
where Tm=mechanical time constant.
To measure the parameters you are asking for, I suggests the following:
A. Measure with an ohm-meter the armature resistance, then apply voltage to the motor without load and measure the current and speed. From equation 1. you can easily derive Ke.
B. Apply nominal current to the motor (with the shaft locked) by means
of a variable voltage source. Measure the torque on the shaft. From this you can derive the torque constant Kt=Torque/Amp.
C. You will find that Kt is approx. equal to Ke
D. For the inertia you can obtain it by calculation from the size and
material of the rotor.
Note1: inductance can be ignored- the electrical time constant is
very short compared to the mech time constant so that it can usually be
ignored.
You can measure the mech time constant by running the motor up to
speed at no load, disconnecting the supply and letting it coast down- plot speed vs time and fit to exponential N=No(e^-t/Tm) time to drop to 36.8% of original speed is the time constant.
Note2: If it is a permanent magnet motor, you can determine the internal emf by spinning it at rated speed and measuring the open circuit voltage. The voltage at any other speed will be directly proportional to speed. To measure the winding resistance, lock the rotor so it doesn't turn and measure the current with a small voltage applied (so as not to exceed rated current) Don't bother using a multimeter's ohm range- not worth the effort.
For inductance, you should use a scope- apply a voltage, rotor locked and look at the current trace vs time.
This will be of the form i=K[1-e^Rt/L] where i is the current at time t.
In most cases the inductance can be ignored as its effects are generally swamped by the mechanical inertia in transient cases and is of little importance for steady state.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.