16
Drive power precautions for NY412x/NY4140
16.1
Drive Power Filtering for NY412x/NY4140
16.1.1
Introduction
The PWM principle applied in the NY4120, NY4125 and NY4140 implies an
unavoidable ripple current in the drive power connections of the bridge
circuits. This ripple current has a peak-to-peak value equal to the average
motor current and a frequency equal to the PWM frequency. Without
adequate filter provisions, this ripple current will in many applications cause a
severe ripple voltage at the drive power input to the NY4120, NY4125 and/or
NY4140 and the node. This ripple voltage may in turn result in malfunctioning
of the NY412x/NY4140 and may in extreme cases even cause permanent
damage.
The capacitors required for the filtering of high-power applications are rather
large, and for this reason they are not included in the on-board capacitance
of the NY412x/NY4140. Bosch Rexroth has designed on-board capacitors in
the NY412x/NY4140 for light applications only. For the heavier applications,
the drive modules need a larger application dependent capacitor in parallel
as close as possible to the I/O backplane.
In principle, the output capacitance normally included in the drive power
supply can perform the necessary filter function, but if the drive power supply
is not placed immediately next to the NYCe 4000 node, the wiring inductance
dramatically reduces the effectiveness of this capacitance.
In EVERY heavy application, it is the customer’s responsibility to
ensure that an adequate drive power filter capacitance is installed
on or immediately next to the I/O backplane of a NYCe 4000
node. Neglecting to do so may result in unstable behavior of the
NY412x/NY4140, and possibly even in permanent damage. See
the NYCe 4000 Standard Housings and Accessories Manual,
chapter "NY4921 Filter Capacitor kit" for installation details and
more information.
The standard systems have a separate drive power input connector for every
NY4120, NY4125 and NY4140. The following paragraphs give background
information, selection criteria and describe solutions for the standard systems
with NY4120, NY4125 and/or NY4140 drives. For less demanding
applications and/or for customer-specific I/O backplanes, an optimal
capacitor can be chosen with confidence.
There are three main criteria for selecting a capacitor:
1. Ripple current of power supply
2. Internal series resistor of the capacitor (ESR)
3. Required voltage
Ripple current
The rms ripple current must be calculated per NY4120/NY4125/NY4140 drive
module. In the calculations the following assumptions must be made:
●
The total ripple current is calculated by adding up the ripple current of all
axes connected to the drive module.
NYCe 4000 Multi-axis motion control system Hardware Sys‐
tem Manual
213/233
Drive power precautions for NY412x/NY4140
R911337671_Edition 18 Bosch Rexroth AG
