PowerPact B Circuit Breaker Wiring Diagrams

PowerPact B DC Systems

Selection of a dc circuit breaker is based on the type of dc system, the rated voltage, and the maximum short-circuit current at the point of installation.

DC Systems

Distribution	Faults	Fault Comments	Worst Case
Ungrounded Source	Fault B	Isc maximum Both polarities (positive and negative) are involved in the fault.	Simultaneous faults at A and D or C and E Either polarity may be involved at voltage V NEC250.167 (A) requires that ungrounded DC systems must have a ground-fault detection system. In order to avoid a double fault condition on ungrounded DC systems, use a ground-fault detection system to detect the first fault and clear it with no delay. *.
	Fault A or C	No consequences.
	Faults A and D or Faults C and E	Isc max Either polarity may be involved at voltage V.
Grounded Middle Point	Fault B	Isc maximum Both polarities (positive and negative) are involved in the fault.	Fault B Each polarity may be involved at voltage V/2.
Grounded Middle Point	Fault A or C	Isc < Isc maximum at V/2 The negative or positive polarity is involved.	Fault B Each polarity may be involved at voltage V/2.
Grounded Negative	Fault A	Isc maximum Positive polarity is involved in the fault.	Fault A All poles taking part in breaking must be placed in series on the positive polarity. If the negative polarity is grounded, an additional pole must be provided to be used for isolation of the negative pole but not for breaking.
Grounded Negative	Fault B	Isc maximum Both polarities (positive and negative) are involved in the fault.