EPOS4 / IDX: Checking the motor current draw

Topic:

• How to read the motor's current draw by an EPOS or IDX?

Solution:

Basics:

The motor current is NOT(!) identical with the current reported by the power supply of the motor controller. The current display of the power supply or measurements with a multimeter are therefore misleading with regard to the motor current.

The motor control is a so-called power converter, i.e. the current and voltage at the motor varies permanently and only the power output from the power supply (= current x voltage) and the power output to the motor correspond (if losses are neglected).  More detailed information on this topic can be found in the following linked Support Center document:

-> Motor controllers: Input current versus Motor current, Power Conversion
 

EPOS Studio's "Data Recorder":

You can easily record the motor current by EPOS Studio's "Data recorder".
Select "Current actual value averaged" by one of the recorder's channels:

Remark:
If you want to share any recordings with maxon's support team, please right-click in the stopped graphics and select "Save Recorded Data". Attach the resulting *.csv file to your support request then. Do not(!) just provide a screenshot. Screenshots are not sufficient for any in-depth analysis. 

Reading motor current by a master controller:

If you want to read out the motor current from your master application (e.g. on a PLC, PC, Raspberry Pi, microcontroller), the object "Current actual value averaged" (0x30D1/01) must be accessed.

Remark:
When using the "EPOS Command Library" (by a PC or Raspberry Pi application code) the function  call "VCS_GetCurrentIsAveragedEx" can be used to read out the motor current.

General remark:

Always record or read the "Current actual value averaged" (0x30D1/01) which is a filtered value. The "Current actual value" (0x30D1/02) has a lot of noise due to current measurement principle.

Cross reference:

• Motor controllers: Input current versus Motor current, Power Conversion
• Motor current measurement in case of a PWM power amplifier
• What is the power consumption of a controller?
• EPOS4 / IDX: Calculation of the electrical motor power
• ESCON: Checking the motor current draw