ETEL Doc. - Operation & Software Manual # DSC2P 903 / Ver. F / 3/6/05 Chapter C: System functions
Operation & Software Manual
Direct Drives & Systems 93
Remark: It may happen that, during a periodic movement (machine cycle), parameter K84 may temporarily
be overcome, and the integrator may not entirely be empty at the end of the cycle. In that case,
after several cycles, an I2T ERROR error (M64=4) is displayed. The cycle is then called an
unstable cycle.
Caution: All software protections described above cannot protect at 100% a motor against overheating;
calculation of the energy balance in the whole system is required to avoid overheating.
Thus, ETEL cannot be hold as responsible in case of system failure due to motor overheating.
The next example explains how to calculate parameters K83, K84, K85. Some information concerning the
system configuration has to be known.
Motor:
I
m
peak: Motor peak current [A] (this is also the max current of the application).
I
m
continuous: Motor continuous current [A].
t: Maximum time at I
m
peak before an i
2
t error [s].
I
over
current: Ultimate motor current value, for a motor OVER CURRENT error [A] (= I
m
peak [A] + 20%)
Controller:
I
max
controller: Maximum current of controller [A] = M82 / 100
Parameter K83 motor over current limit:
Parameter K84 i
2
t rms current level:
Caution: If a 2-phase linear motor performs a back and forth movement with very short strokes, only
one phase will be used. Thus, thermal load will be concentrated on the half of the motor
surface. Take parameter K84, (value obtained with formula above) and divide it by 2: K84
short_stroke = K84 / 2.
Parameter K85 i
2
t integration limit (energy):
K85
Current I
t
t
K83
K84
It
2
error
M67 (integral)
K83
I
over
current 32768⋅
M82 100⁄
----------------------------------------------
=
K84
I
m
continous
M82 100⁄
---------------------------
100⋅
2
0.8192⋅
=
K85 9830 t
I
m
peak
M82 100⁄
------------------------
100⋅
2
I
m
continuous
M82 100⁄
------------------------------------
100⋅
2
–
⋅⋅=
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