The difference is the step down transformer that provides the power for the internal circuitry. On the 277 single phase the transformer is 277 VAC to 24 VAC and you will note that its primary winding is connected to the top and middle poles on the contactor.
On the 277/480 three phase unit the transformer is 480VAC to 24VAC and the primary winding is connected to the top and bottom poles on the contactor.
Consult a professional and or your electric provider to determine what configuration is needed.
Click here to view an informative PDF about wiring for the APS-4C and SC-40C
