Elmo SERVO AMPLIFIER DBP SERIES - Manual (Page 20)

19
DBP - Rev 6/93
This function should be activated whenever the rated current AND the peak
current of the motor are less than 20% of the amplifier rated continuous and
peak limits respectively.
Sometimes, oscillations may occur in the current loop due to the fact that
the feedback gain was multiplied. This can be resolved by substituting R4 with
a lower value.
4.3 Digital current limits
The servo amplifier can operate in the following voltage-current plane:
-Ip -Ic
+V
Ic Ip
Intermittent
zone
Continuous
zone -V
Ic - Continuous current Ip - Peak current
Fig. 4.1: Voltage-Current plane
Each amplifier is factory adjusted to have this shape of voltage-current
operating area with rated values of continuous and peak current limits. By
using the command CL(n) for the continuous and PL(n) for the peak it is
possible to adjust the current limits (continuous and peak independently) from
the rated values down to 10% of the rated values.
4.3.1 Time dependent peak current limit
The peak current duration is a programmable parameter which is also a
function of the peak amplitude and the motor operating current before the peak
demand. The user defines the maximum duration of the full amplitude peak by the
instruction PDn - n cannot be more than 2 seconds. In addition to this
definition, a digital filter is employed to ensure that the RMS value of the
current will not exceed the continuous current limit. The duration of Ip is
given by: