AC power
Delta connection: line and winding current
- where
- line current (A)
- winding (phase) current (A)
- line voltage (V)
- winding (phase) voltage (V)
Explain this equation
Gives the line current and line voltage of a balanced delta-connected load or winding, from each winding's current and voltage. Useful for motors run in delta and delta transformer windings.
I_ph is the current through one winding and V_ph the voltage across it. I_L is the current in each supply line and V_L the line-to-line voltage.
In delta each winding sits directly across two lines, so it sees the full line voltage. Each line feeds two windings, and its current is the difference of two winding currents 120° apart; adding them as vectors gives √3 times one winding current, not twice.
10 A in each winding gives about 17.3 A in each line. Going the other way, a delta motor drawing 17.3 A per line has 10 A in each winding.
Watch out: to get winding current from line current, divide by √3, don't multiply. Whether a motor can run in delta depends on its rated winding voltage.
Each delta winding is connected across two lines, so it receives line-to-line voltage. The line current is a vector combination of winding currents.
For a balanced load, divide line current by √3 to find winding current. The relationship is not a plain arithmetic addition of two winding currents.
Enter your values to see the result.
Common mistake
Do not multiply line current by √3 when finding the smaller winding current.
Limits
Balanced sinusoidal three-phase delta load. Switching star/delta requires a correctly rated motor and starter; this equation alone is not a wiring instruction.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.