Beckhoff EL72 1 Series Documentation page 18

Product overview
undervoltage, overcurrent, terminal temperature or motor load, offers maximum operational reliability.
Modern power semiconductors guarantee minimum power loss and enable feedback into the DC link when
braking.
Beckhoff sets new benchmarks with regard to size with the integration of a fully-featured servo drive in a
standard EtherCAT terminal – the EL7201 – with a width of just 12 mm. This small manufactured size is
possible thanks to the latest semiconductor technology and the resulting very high power factor. And yet,
despite the small dimensions, nothing has to be sacrificed.
The integrated fast control technology, with a field-orientated current and PI speed control, supports highly
dynamic positioning tasks. Apart from the direct connection of motor and resolver, the connection of a motor
holding brake is also possible.
Connection to the control system
A further big advantage of the EL72x1 is the easy incorporation into the control solution. The complete
integration into the control system simplifies commissioning and parameterization. As with all the other
Beckhoff terminals, the EL72x1 is simply inserted into the terminal network. Then the full terminal network
can be scanned by the TwinCAT System Manager or manually added by the application engineer. In the
System Manager the EL72x1 can be linked with the TwinCAT NC and parameterized.
Scalable motion solution
The servo terminal complements the product range of compact drive technology for Beckhoff I/O systems
that are available for stepper motors, AC and DC motors. With the EL72x1, the range of servo drives
becomes even more finely scalable: from the miniature servo drive up to 200 W in the EtherCAT Terminal
through to the AX5000 servo drive with 118 KW, Beckhoff offers a wide range including the servomotors.
The AM31xx series was specially developed for the servomotor terminal EL72x1.
Thermal I²T motor model
The thermal I²T motor model represents the thermal behavior of the motor winding taking into account the
absolute thermal resistance R and the thermal capacity C of motor and the stator winding.
th th
The model assumes that the motor reaches its maximum continuous operating temperature T during
nom
continuous operation with rated current I . This temperature corresponds to 100% motor load. During
nom
operation at rated current the motor model reaches a load of 63% after a time of τ =R ∙C and slowly
th th th
reaches its continuous operating temperature.
If the motor is operated with a current that is greater than the rated current, the model reaches 100% load
more quickly.
If the load of the I²T model exceeds 100%, the requested set current is limited to the rated current, in order to
protect the motor winding thermally. The load reduces to a maximum of 100%. If the current falls below the
rated current, the load falls below 100% and the set current limitation is cancelled.
For a motor that has been cooled to ambient temperature, the time for reaching 100% load with a set current
that exceeds the rated current can be estimated with τ ∙I ²/I ².
th nom actual
The actual load must be known for exact calculation of the time when the 100% load threshold is exceeded.
18 Version: 3.3 EL72x1