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Selecting a DC Power Supply for a Kinetix 5700 System

When designing a Kinetix 5700 servo system powered from a common DC bus, it is important to properly size the external DC power supply. An undersized supply can lead to nuisance faults, reduced machine performance, and instability during acceleration events. An oversized supply can increase system cost unnecessarily. This article provides a simple sizing method for estimating the minimum continuous power rating required for a Kinetix 5700 DC power supply.

 Sizing Formula

Use the following formula to determine the minimum required continuous output power of the power supply:

Minimum Output Power (kW)


Pmin = (X × Y × 0.6) + (Y × 0.2) 

Where:

Variable Description
X Power rating of the largest motor in the system (kW)
Y Total number of servo axes in the system

Understanding the Formula 

Typical machine duty cycles provide some natural diversity between axes. The factor 0.6 represents a diversity factor for since not all axes operate at maximum power simultaneously. While the additional 0.2 kW per axis accounts for baseline system loading. 

Make sure to add additional capacity if your machine:

  • Multiple axes accelerate simultaneously such as: Gantry systems or Electronic camming applications.
  • High-throughput machines which operate with aggressive motion profiles.
  • Potential Future Expansion.

Select Correct Power Supply

Then take the calculated value of Pmin and find select the Power Supply with a greater Continous Output Power.

Example

System Configuration

Incoming Voltage 480V, 60 Hz, 3 phase

Axis Motor Size
Axis 1 3.0 kW
Axis 2 2.0 kW
Axis 3 1.0 kW
Axis 4 1.0 kW

Largest motor:

X = 3.0 kW

Total axes:

Y = 4

Calculation


Pmin = (3.0 kW × 4 × 0.6) + (4 × 0.2)

Pmin = 7.2 kW + 0.8 kW

Pmin = 8.0 kW

Based on the table above at 480V operation we should use a 2198-P070