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Transformer Sizing

Transformer Sizing for Low Voltage Power Installations

Line Voltage and Low Voltage Actuator Installations.

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Typical industrial electric actuators are powered by line voltage (120vac or 230vac) mostly because of the ease of wiring, power efficiency, and wide availability of actuators and control options.

Low voltage actuators, such as 12vac/vdc and 24vac/vdc, are also used because they:
  • Interface directly to SCADA control systems
  • Are compatible with Solar and Mobile power supplies
  • Provide safety benefits associated with lower voltages

We suggest the following when considering changing an existing installation from 120vac to 12 or 24 volt power.
  • Use INRUSH current for transformer sizing instead of RUNNING current.
  • Carefully consider wire gauge as a function of installed CONDUIT wire run length.
  • Properly size the transformer for a low voltage application
  • Number of actuators being powered from the transformer.

Inrush (starting current): is the additional current required to get the actuator motor moving at load. Inrush current is typically TWICE that of the running current of a low voltage actuator.

Length of Wire Run: Wire has an inherent resistance based in part on the diameter of the wire and its length. ProMation Wire Sizing Charts in our data sheets and IOMs show the maximum suggested wire run which keeps the voltage loss at or below 10%.

Proper Power Supply size: An undersized power supply can and will cause issues such as motor overheating, slow motor movement, wire heating, and possible permanent motor damage. Be sure to use the proper power supply.

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