4.1.2 Choosing a power supply
In any application with servo drives, the power consumption and regenerated power must be taken into
account. An unstable power line causes harmful harmonics and could damage the system. In most
applications, there is more than one drive which requires an accurate sizing of the DC bus. A system with
minimum failure rates and little power consumption can be realized by properly sizing the bus capacitors,
braking choppers, power supplies, cabling, earthing and using the right connectors. It’s recommended to use
a protected extra-low voltage supply (PELV) instead of a safety extra-low voltage supply (SELV). If a SELV is
used, it’s possible that the isolation from the earth can be violated through the servo drive (e.g. through
heatsink or mechanical mountings) and the supply becomes PELV.
4.1.2.1 Supply voltage definitions
The nominal supply voltage is the voltage that we recommend to set on your power supply (or use a
battery that is within this range).
Maximum voltage ratings divide into continuous maximum and peak maximum ratings. The maximum
continuous voltage is a voltage that can also be set on your power supply / battery, if all voltage-related
effects are well under control. In particular, it must be made sure that neither recuperative braking nor high
frequency (typically 32 or 64 kHz) voltage ripple lead to exceeding the allowable maximum continuous voltage
value permanently or cyclically. The peak maximum voltage should never be reached in regular operation. It
can only be used as a reserve for rare events, no longer than 1 second and not repeatedly.
The minimum voltage is for configuration purposes only.
4.1.2.2 Regenerated voltage
Electrical motors are reversible machines that can act as a motor or generator. When a voltage is applied to
the motor, a torque is generated that causes acceleration. But the motor will generate power during
deceleration. Regenerative energy can be a serious issue when high inertia, low friction axes undergo fast
deceleration. If no counter-measures (particularly adding a braking chopper to the circuit) are taken, the
voltage in the DC bus will rise beyond the overvoltage threshold of the servo drives which will cause the
drives to switch off and thus the system will become uncontrollable. The problem will be exceeded in multi-
axis applications with heavy loads that are affected by gravity. For details, please see section Regenerative
energy
Synapticon Documentation
© 2021 Synapticon GmbH | Daimlerstraße 26 | D-71101 Schönaich Documentation v 4.19.0 | Built 2022-02-01
961/1031
