How is margin converted to account currency after position close?

[des32]

If I open position with pair AB where base currency A is different from my account currency C, I need AC ASK price to calculate required margin.

What happens when I close my position? Is the margin converted back to my account currency via AC BID price? Does it mean I can loose my equity on AC spread/price movement?

Please post some article explaining this problem (I couldn't google anything).

[William Roeder]

Margin isn't converted to anything. Your broker reduces your available equity (free margin) by the amount he charges per lot per symbol. On close he increases it. No exchange rates required.