The temperature-rise (△T) of bars can be calculated with
following formula:
△T=Tr – Ta
Tr: temperature of bars with rated current ( for general
electrical apparatus, Tr should be ≤105℃).
If your operating ambient temperature is 40
℃,
and you need ampacity 510A with bar width < 40mm, you could get
allowed highest temperature-rise 65K (105℃-40℃=65K), so you
could decide dimension 32×1×4. With this bar, the highest
temperature-rise will be 50K with current 520A.