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IMS-MN-LMDE42C_A
Auxiliary Power Supply
Liberty MDrive Ethernet TCP/IP
Auxiliary Power Supply
The auxiliary logic supply is an optional power supply used to provide power to the logic
circuitry of the LMD in the event of main system power failure. This supply will retain data such
as position.
There are no special considerations required when choosing this supply beyond:
Voltage .................................................................................................................................................+12 to +24 VDC
Current .................................................................................................................................................200 mA/LMD
Wiring and Shielding
Electrical “noise” (interference) is always present in a system that involves high power and
low signal circuitry. Regardless of the power configuration used in the system, there are some
wiring and shielding rules that should be followed to keep signal-to-noise ratio (SNR) as small
as possible.
Rules of Wiring
• Power Supply and Motor wiring should be shielded twisted pair, and these lines should not
run parallel to signal carrying wires.
• Power ground return should be as short as possible.
• For installations which utilize separate electric motor drives and stepper motors, wiring
between the driver and motor should be shielded twisted pairs using 20 gauge wire for
motor current less than 4.0 amps and 18 gauge or better for motor current 4.0 amps or
higher. A common mode choke may be required in each of the motor phase lines to reduce
shield current levels.
• Power Supply wiring should be shielded twisted pairs. Use 18 gauge wires if load is less than
4 amps, or 16 gauge for more than 4 amps.
• Never use a “daisy-chain” power supply wiring scheme to system components. This type of
power distribution will result in degraded system reliability and performance as a result of
poor EMC and ground-loop issues. In cases where ‘daisy-chaining” is unavoidable, the user is
responsible for final system reliability and performance. The use of conservatively selected
wire gauge and the use of decoupling capacitors
(i.e., a combination of capacitors to provide for acceptable low frequency and high
frequency noise reduction) at each electronic drive should be considered as a minimum.
Rules of Shielding
• The shield must be tied to zero-signal reference potential. In order for shielding to be
effective, it is necessary for the shield to be earthed or grounded.
• The shield must be connected so that shield currents drain to signal-earth.
• The shield should be tied to a single point to prevent ground loops.
