Worked example
No result for these values. The message above the form says which field to change.
Secondary current at the measured primary current
3 A
- Nominal current ratio
- 20 :1
- Primary current as a share of rating
- 60 %
- Lead-loop burden at rated secondary current
- 2.5 VA
- Connected burden, conservative sum
- 3.5 VA
- Rated burden headroom
- 1.5 VA
- Equivalent connected impedance, conservative
- 0.14 Ω
The conservative burden sum is within the CT rated burden. Instrument burden must be quoted at the selected rated secondary current. This does not approve CT accuracy, saturation, fault duty or physical fit.
Underlined figures are rounded. Select one to copy its full value.
Method and assumptions
Formula
Is = Ip ÷ (Ip,rated ÷ Is,rated); VAlead = Is,rated² × Rloop; VAtotal = VAinstrument + VAleadWiring burden is checked at rated secondary current. Expected output at the entered measured primary current is reported separately.
Limits of this result
- For conventional current-output CTs with an external burden. This tool is not for voltage-output CTs or Rogowski coils.
- Ratio and rated burden do not establish accuracy class, saturation, fault duty, insulation rating or aperture fit.
- Enter the resistance of the complete outgoing-and-return secondary lead loop at its operating temperature.
- Enter instrument burden at the selected rated secondary current. For unchanged impedance, burden at another current scales with the square of current.
- Adding instrument VA magnitude and resistive lead VA is a conservative arithmetic sum, not an exact complex-impedance calculation.
Technical sources
Put the value to work
Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.