Rockwell Automation 1398-DDM-xxx USE MNL/ULTRA 200 DIG.SERVO.DR - Manual (Page 275)

Publication 1398-5.0 – October 1998
Creating Custom Motor Files D-11
Inductance
The inductance value is the measured phase-to-phase inductance in
milliHenries of the stator winding. The inductance is used to set the
current regulator gains, and is critical to current loop performance.
The inductance value can be in the range from 0.0039 to
255.9961mH.
The ratio of motor inductance to motor resistance is defined as the
electrical time constant of the motor. Always verify this value is in a
reasonable range. Electrical time constants less than ~1mS, and higher
than about ~50mS, present difficulties in the current regulator and
should be avoided.
Inductances less than ~1mH suffer from high current ripple, and are
not recommended for use with the ULTRA 200 Series drives.
Some manufacturers specify the inductance in milliHenries/phase.
The phase-to-phase inductance is twice the per phase value.
Rating Parameters
Continuous Torque
Continuous torque specifies the rated current of the motor in peak
Amps. (Note: Continuous torque is peak Amps, rather than rms.) The
drive uses the continuous torque current value in its motor thermal
protection software. The drive generates a fault if the square of the
actual current, after passing through a low pass filter, exceeds the
square of the continuous torque current value. The square is used
because the power dissipation in the motor is approximated as I
2
R
losses. The continuous torque value may be in the range from 0.0078
to 255.9922 Amps.
Some manufacturers specify the rated current of a motor in rms Amps.
To convert from rms Amps to peak Amps, use the formula:
Occasionally a manufacturer specifies only the rated torque, and does
not include the rated current specification. In such a case, the rated
current can be computed using the rated torque and the torque
constant. A factor of 1.1 is included to allow for degradation of the
torque constant at high temperatures, etc. The formula, assuming the
torque constant has already been converted to N-m/A(peak), is:
Intro
1 Amps Amps(rms)
⋅ = ⋅
1 414 .
Intro
I 1.1
rated torque in N m
K
RATED
T
= ⋅
⋅