1.3.1.3 Thermal mounting considerations
While the maximum peak current is a fixed property of a servo drive, the maximum continuous output
current is highly dependent on its thermal integration into the surrounding system. The boundary conditions
described below are idealized scenarios that can be described and defined clearly. In most cases they will not
represent the real-world application exactly, as the geometric and thermodynamic situation in a robot or
other application is typically more complex. The purpose of these exemplary scenarios is to provide the
system designer with an estimation of the required cooling capacity of the structure surrounding the
SOMANET servo drive.
1. Application integration defined by interface temperature
In this scenario, the servo drive is assumed to be integrated into a structure that is cooled externally to a
defined maximum temperature. The defined continuous currents are achievable as long as the drive is
bolted to a metal structure using all 4 M3 screws, the entire red aluminum bottom is in contact with the
structure and all of the contact surface cooled to no hotter than the temperature specified in the figure
below. This way of specification is the most accurate one and can directly be used in the design process of
the system.
2. Application integration on a sample plate in air *
2.a Application Integration Defined by Ambient Temperature
In this scenario, the servo drive is mounted to a geometrically defined structure. As “real-world structures”
are typically too complex to reflect them here, a simple geometry (rectangular aluminum plate of 250 x 250
x 20 mm) was selected. The drive is bolted to the center of a metal plate of such geometry using all 4 M3
screws, the plate is mounted vertical and the rest of the metal plate is surrounded by ambient air.
Depending on the temperature of the ambient air, the continuous currents specified in the figure are
achievable. It will be subject to free convection cooling. The available continuous currents can be further
increased when adding active cooling (fan).
2.b Application Integration Defined by Geometry
As in the scenario above, the drive is mounted to the center of a vertical aluminum plate. Here, a fixed
ambient temperature (20°c) is assumed, but different sizes of the plate are considered. Depending on the
size of the plate, the continuous currents specified in the figure are achievable. The available continuous
currents can be further increased when adding active cooling (fan).
3. Servo drive floating in ambient air
This is a reference value when not integrating the node into any structure. As SOMANET servo drives are
designed as embedded products, this situation is not recommended for both thermal and mechanical
reasons!
Attention
A similarly bad cooling situation will be created if the node is mounted to a structure with poor
thermal conductivity, in particular structures made of plastic.
* The continuous phase current given in the specsheet provided by Synapticon assumes this kind of
boundary condition with a 200 x 150 x 20 mm aluminum mounting plate.
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