Solar & DC
PV DC Isolator Rating Calculator
Screen the minimum voltage rating, current rating, utilization category, and pole configuration for a PV array DC isolator (disconnector). A DC isolator must break the array under load at full string voltage, so its ratings come from the cold open-circuit voltage and the short-circuit current, not the nominal figures.
How the ratings are set
The isolator has to open while the array is generating, so it must interrupt a DC arc at the highest voltage the string can reach — the cold open-circuit voltage. The current rating carries the array short-circuit current with a continuous-duty margin, because a PV source sits close to its short-circuit current in normal operation.
Why DC-PV2 and series poles
The DC-PV2 utilization category (IEC 60947-3) certifies a switch to make and break a PV array on load, including the arc energy of a DC source with no natural current zero. As with DC breakers, the voltage rating is reached by putting poles in series so each shares the arc voltage — a 1000 V array typically needs several poles internally connected as the manufacturer specifies.
Frequently asked questions
Where is a PV DC isolator required?
An accessible load-break isolator is normally required at the array and at the inverter so the DC side can be safely disconnected for maintenance. Local rules and IEC 60364-7-712 set the exact positions.
Do I size current on Isc or Impp?
On Isc with the continuous margin. A PV source’s operating current sits close to its short-circuit current, so Isc × 1.25 is the conservative continuous rating.
How many poles do I need?
Enough that the device’s per-pole DC voltage, multiplied by the series poles, covers the cold string voltage — the manufacturer states the configuration. Do not reduce poles to save space.
Select the DC isolator
Match the DC-PV2 rating, voltage, current, and poles to an isolator for the array or inverter position.
Screening estimate for guidance only. Final isolator ratings, category, and pole configuration must be confirmed by a qualified person against the manufacturer’s DC data and the array design.