B-65302EN/01 SPECIFICATIONS FOR THE βiS SERIES 3.SELECTING A MOTOR
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The duty calculation procedure is shown below:
<1> Calculate Torque percent by formula (b) below.
<2> Motor can be operated at any point on and inside the curve
(according to the limits by overheating or overcurrent alarms)
corresponding to the given over load conditions obtained form
<1>.
<3> Calculate t
F
by formula (a)
)(
)(1
100
b
torqueratedContinuous
torqueLoad
TMD
a
tDutypercen
tt
RF
−−−=
−−−−×=
÷
÷
ø
ö
ç
ç
è
æ
t
F
: "OFF" time
t
R
: "ON" time
The values of t
R
and t
F
obtained form the above mentioned procedure
shows the ones limited by motor thermal conditions.
The motor temperature limits for determining overload duty curves
are determined according to the motor temperature limit (overheat
alarm) and according to the soft thermal function of monitoring the
current by servo soft for a rapid increase in temperature (overcurrent
alarm).
The overload duty characteristic determined according to the overheat
alarm is represented with a curve within a relatively long time range
of at least about 100 seconds of the load time. That determined
according to the overcurrent alarm is represented with a curve within
a relatively short time range of up to about 100 seconds. The final
overload duty characteristic is represented with the curve described
using either characteristic value, whichever is shorter. For the soft
function of monitoring overcurrent, the settings differ depending on
the motor. If the motor is in the overload status at a motor speed of
about 0, an overcurrent (OVC) alarm may be issued for a time shorter
than described. Note that another restriction may be imposed
depending on the use condition since driving device (such as an
amplifier), Pulsecoder, and other devices contain a thermal protection
device.