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Thermal Characteristics
The drives are specified to operate at a 45° C ambient. This is not a maximum safe
operating specification. There are no parts in the drive that cannot operate at a 60° C
temperature. The absolute maximum temperatures that the drive can operate at are
determined by thermal switches on the bridge switch power devices (IGBT's) and on the
shunt loads. These thermal switches open and disable the drive at 85° C.
At temperatures above 45° C the amplifier's ability to produce its continuous rating is
impaired by the heat rise from the ambient temperature. The amplifier will thermally shut
down once the 85° C condition is sensed at either the bridge or the shunt load.
A guideline for enclosures would be to assume that the amplifier's thermal losses are 16
times the continuous rating +50 watts. The 50 watts is required for the logic supplies.
If the application is causing bus pumping, and the shunts are being used the thermal rise
from the shunts is restricted to 85° C and the actual power rating of the shunt load. Add
the Continuous Watts from the Shunt Loads to the amplifier thermal losses if the
application is bus pumping.
The drives can be supplied with different shunt loads as options and in some instances it
is a requirement to mount the shunt loads external of the amplifier.
"-EXS" Option
In high inertia applications, energy stored in the load must be dissipated in the amplifiers
bridge, bus capacitance and parallel shunt load. In certain machining operations, multiple
passes are required and the heat rise from this energy cannot be dissipated in the
amplifiers internal shunt without causing an amplifier thermal fault. The "-EXS" option
provides a means of mounting the shunt load outside of the amplifier.
The "-EXS" suffix applied to the amplifier model provides for the interconnection of the
external shunt load.
There are two available external shunt load. It is designated as:
EXS-50-460
EXS-100-460
This shunt load has two 100 CFM fans and electric heaters for load resistors. They are
also equipped with a thermal shut down switch.
The shunt load should be mounted external to the amplifier enclosure but within four feet
of the amplifier. The wiring can be accessed through a 3/4" seal tight connection with an
optional cover or it can be wired directly.
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