Guide

Why a DC Circuit Needs a DC Rated Breaker

An AC breaker fitted to a solar string is one of the most common sourcing mistakes on the DC side and the reason the DZ47Z-63 series exists.

Alternating Current Helps the Breaker

In an AC circuit the current passes through zero twice per cycle. That natural zero crossing gives the arc drawn between opening contacts a moment to extinguish. The breaker design relies on it.

DZ47Z-63 3P DC MCB on DIN rail front view — DZ47Z-63 Solar MCB

Direct Current Does Not

A DC circuit has no zero crossing. The arc is continuous and must be stretched and cooled until it fails. A DC rated device is built with the arc chute geometry and contact gap needed to do that, which is why its ratings look different from an AC device of the same physical size.

Htst1-c series 4P surge protector on 35mm DIN rail front view — SPD

What the DC Ratings Mean

The DZ47Z-63 series is specified for DC 12V to DC 1000V operation with a rated insulation voltage of 1200V DC, a 4kV rated impulse withstand voltage and an ultimate breaking capacity of 4.5kA at 100 percent service breaking capacity. Rated current runs from 1A to 63A with a Type C thermal magnetic characteristic.

HTH2-125 3P disconnector circuit breaker on DIN rail front view — HTH2-125 Disconnector circuit breaker

Pole Count on a String

Poles from 1P to 4P are available. How many conductors must be broken depends on the earthing arrangement of the array, so it is worth sending a single line diagram with an enquiry rather than ordering by current alone.

Where It Goes in the System

String protection in a combiner box, battery bank isolation and DC control circuits inside inverter panels are the usual positions. Isolation for maintenance is a separate function, covered by a disconnector.