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Digitax HD M75X Series Installation and Technical Guide
Issue Number: 5
5 Multi axis system design
There are a number of important considerations for multi axis systems, it is recommended that the design process follows the following method:
1
. Determine the power profile of the system and select the most appropriate parallel DC bus, drive and motor configuration to meet the demands of
the power profile (refer to section 5.1 below).
2
. Assess DC bus paralleling connection method, external 24 Vdc, dynamic braking, EMC filter and fieldbus communication requirements, refer to
DC bus paralleling connection method
EMC filters for multi axis systems
3
. Choose the mechanical installation method, refer to section 5.7
Multi axis system installation
An example applying these steps is given in section 5.8
Example design of a multi axis system
5.1 Multi axis system power profile and configuration
The power profile of one complete worst case duty cycle should be calculated in watts from the product of rated speed (radians/sec) and torque (Nm)
for each axis. The sum total instantaneous power of the all axis over one complete duty cycle should also be calculated.
Individual drives should be selected to meet the power requirements of each axis.
The power profile of the whole system (including all axis) should be used to determine which DC paralleling configuration is the most suitable.
5.1.1 DC bus paralleling configuration
Connecting the DC links of several drives together allows regenerated/braking energy from one drive to be re-used by another motoring drive. This
improves the efficiency of the system since the regenerated energy is not wasted in braking resistors and the motoring drive draws substantially less
power from the mains. This can be particularly advantageous where one or more drives may be 'holding back' a line to provide tension. It is often
applied in high performance servo drive applications where substantial amounts of energy is used in accelerating and braking motors/machines.
As well as offering advantages in terms of simplifying energy management, a common DC bus system also has the potential to simplify the mains
connections and protection.
The following parallel DC bus configurations cover single AC mains feed only.
There are a number of different ways of connecting Digitax HD M75X drives together and paralleling the DC bus.
5.1.2 DC paralleling using a Digitax HD M75X rectifier to provide the DC supply
In this configuration multiple drives can be connected together via a parallel DC bus from a single AC feed to create a frame block. A frame block can
be comprised of Digitax HD M75X series drives of different frame sizes and current ratings.
Drives of different voltage ratings cannot be mixed on the same frame block.
Only one AC input should be connected to a system using a common DC bus.
NOTE
NOTE
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