4NC5222-2DE21

What does this current transformer do in an electrical panel?

It reduces a high primary current flowing through a cable or busbar to a standard 5 A secondary current that can be measured by meters, analysers, or energy monitoring equipment. This model is designed for metering applications and provides an accuracy class of 0.5.

What is the transformation ratio and what does it mean in practice?

The ratio is 200/5 A. That means when 200 A flows through the primary conductor, the secondary output will be 5 A (with the specified accuracy when used within its rated burden). At 100 A primary, you would expect about 2.5 A secondary.

Is it suitable for energy metering and monitoring rather than protection?

Yes. With accuracy class 0.5 and a 5 VA rated burden, it is intended for measurement tasks such as energy monitoring, building services metering, and industrial sub-metering rather than protection-class applications.

What does the 5 VA rating mean and why does it matter?

5 VA is the rated burden (apparent power) the transformer can drive while maintaining its specified accuracy. The total burden includes the connected instrument input burden plus the resistance of the secondary wiring. If the burden is too high, measurement accuracy can be adversely affected.

What size cable or busbar can pass through the opening?

The opening height is 30 mm. The maximum outer diameter of a push-through conductor is 28 mm. For busbars, the maximum push-through width is up to 30 mm (depending on configuration).

How is it mounted?

It is designed for screw fixing. This makes it suitable for secure installation on panel backplates and within switchboards where the conductor passes through the transformer window.

What type of secondary terminals does it use?

The secondary connection is via screw-type terminals, which are commonly used for reliable termination of secondary wiring in metering circuits.

Can it be used on single-phase or three-phase systems?

It can be used on any single conductor. For three-phase measurement, one transformer is typically installed per phase (three units total) so each phase current can be measured.

What environmental conditions is it designed for?

It is specified for operation from -30 °C to +55 °C. This covers typical indoor switchboard environments in commercial and industrial installations.

What is the ingress protection rating and what does it imply?

It is rated IP20. This indicates it is intended for installation inside an enclosure where access to live parts is controlled, rather than for exposed or outdoor mounting.

What standards does it align with for metering current transformers?

It is part of a range designed in line with commonly used current transformer standards for measurement applications, including EN 61869-1 and EN 61869-2.

Are there any important considerations for the secondary circuit during installation?

Yes. The secondary circuit should not be left open-circuit while primary current is flowing. If the meter is not connected yet, the secondary should be shorted using an appropriate shorting link or terminal arrangement until the measuring device wiring is complete.

How much space does it take up in a panel?

Typical overall dimensions are approximately 78.5 mm (height) × 60 mm (width) × 65 mm (depth). This helps when checking clearance around busbars, cable bends, and adjacent components.

Is this transformer intended for low-voltage systems?

Yes. It is used in low-voltage switchboards and distribution panels where current measurement is required. In the Siemens 4NC5 family documentation, a maximum equipment voltage of 720 V is referenced for the range.