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Using a DC Power Supply for AKD Bus Power

Many servo applications exist in which it is more practical to use a DC power supply for the motor bus power instead of using AC power.  Some of these include the use of batteries, generators, low voltage DC power supplies, and there are cases where high voltage DC power supplies are used just because of preference or availability.

The following applies to the AKD-x003y through AKD-x024y, where y = 6 or 7 (All AKD drives except for the AKD48).

It is possible and allowable to run the AKD drive on a DC power supply for the motor power.  The DC power can be applied to the AC mains input terminals L1 and L2, or directly to the DC bus terminals.  The bridge diodes in the AC input stage are sized appropriately to handle the DC current.

For the following two conditions, the DC power MUST be applied to the L1 and L2 AC input terminals:

  • If the external DC power supply can NOT accept returned energy (power generated by the motor).
  • If the external DC supply is NOT soft started (to limit inrush current to the bus capacitors).

The AC input stage can accept DC power for normal operation.  This means you can wire the DC power supply to L1 and L2 for charging the DC bus capacitors and leave it there for powering the motor during normal operation.  There is no need to switch the DC power between the AC input terminals and the DC bus terminals.

For the following conditions, the DC power MUST be applied directly to the DC bus terminals:

  • If the external DC supply is soft started (to limit inrush current to the bus capacitors) AND you want to share energy returned to the supply due to slowing down a motor (power generated by the motor).

Protections built input the DC power supply should be considered to ensure a safe system that could be UL approved.  The AKD drives in of themselves are not UL approved to be powered by an external DC supply.  If the supply is appropriately protected per UL requirements, then it can be approved.  Mostly the current needs to be limited to equal or less than the rated AC line fuses we specify in the manual for normal AC line connection.

The AKD2G drive follows the AKD design capabilities and constraints regarding DC power.