What is the adjustable breaker sizing for a 45kva transformer

The adjustable breaker sizing for a 45kVA transformer depends on several factors, including the transformer's primary and secondary voltage ratings, the load current, and the desired level of fault current interruption.

Here are some general guidelines to consider:

  1. Primary side: The primary side breaker should be sized to handle the maximum fault current that can occur on the primary side, which is typically 1.5 to 2 times the rated current of the transformer. For a 45kVA transformer, the primary side current rating is typically around 25-30A (45kVA / 230V primary voltage). Therefore, the primary side breaker should be sized to handle a fault current of around 37.5-60A (1.5-2 times 25-30A).
  2. Secondary side: The secondary side breaker should be sized to handle the maximum load current, which is typically the rated current of the transformer. For a 45kVA transformer, the secondary side current rating is typically around 200-250A (45kVA / 230V secondary voltage). Therefore, the secondary side breaker should be sized to handle a load current of around 200-250A.
  3. Adjustable breaker sizing: To determine the adjustable breaker sizing, you need to consider the maximum fault current that can occur on the secondary side, which is typically 1.5 to 2 times the rated current of the transformer. For a 45kVA transformer, the maximum fault current on the secondary side could be around 300-500A (1.5-2 times 200-250A).

Based on these guidelines, here are some possible adjustable breaker sizing options for a 45kVA transformer:

Please note that these are general guidelines and the actual breaker sizing may vary depending on the specific transformer design, installation, and application. It is recommended to consult the transformer manufacturer's specifications and guidelines, as well as local electrical codes and regulations, to determine the appropriate breaker sizing for your specific application.