Which Shelly device does this 400A transformer work with?

It works only with the Shelly Pro 3EM-400 energy meter; it is a measuring accessory and cannot operate on its own or with other meters.

How many transformers do I need for a three-phase installation?

Usually three units, one per phase, wired to the matching inputs of the Pro 3EM-400 for complete three-phase metering.

Do I need to disconnect the cable to fit the clamp?

No. The split-core design with screwless mounting lets you place the clamp around the existing conductor and secure it with cable ties on both sides.

What conductor size fits inside the clamp?

The conductor aperture is 35 mm and the maximum primary current is 400 A, which covers large-section cables in power panels.

Can I install this transformer myself?

Installation involves work inside the electrical panel and must be done by a qualified electrician; CasaSmart can plan the integration with the Pro 3EM-400.

In what environmental conditions can it operate?

It operates from -10 °C to 50 °C, at 0 % to 80 % RH and up to 2000 m altitude.

Shelly 400A CT for Pro 3EM-400

Name: Shelly 400A Current Transformer for Pro 3EM-400
Brand: Shelly
SKU: SHELLY-CT-400A-PRO-3EM-400

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What it is, who it's for, what it does

About this product

This current transformer extends the Shelly Pro 3EM-400 energy meter to high-power circuits. With a maximum primary current of 400 A and a 3000/1 turns ratio, it measures consumption on industrial three-phase installations without interrupting the conductor.<br><br>The split-core ferrite design with screwless snap-on mounting lets you place the clamp around an existing cable and secure it with cable ties on both sides. The 35 mm conductor aperture and the 650 mm cable with a 2-pin MX3.0 connector plug directly into the meter's dedicated terminals.<br><br>It is an accessory that works only together with the Shelly Pro 3EM-400 and has no connectivity of its own. Panel mounting must be carried out by a qualified electrician.

Delivery
Free from 1500 MDL
Returns
30 days to return
Warranty
24 months

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Where it works

Use cases

A production hall in Chisinau tracks consumption on each phase and spots power peaks.

Three 400A transformers on the phases of a high-power panel, wired to the Pro 3EM-400.

An electrician adds energy metering on the main incomer of a commercial building.

The clamp fits screwless onto the main conductor without cutting the supply.

A business center splits consumption among tenants based on real measurements.

Pro 3EM-400 data is used to allocate electricity costs.

For the installer

Technical specifications

full spec · wiring · datasheet

Power

Rated max. primary current: 400 A
Primary/secondary current ratio: 3000/1
Electrical strength: 3000 VAC, 60 sec

Physical

Core: Ferrite, split-core
Conductor aperture: 35 mm
Size (HxWxD): 84x54x48 ±0.5 mm
Weight: 290 ±1 g

Connectivity

Cable length: 650 mm
Connector: 2-pin MX3.0-2x1Y
Compatible meter: Shelly Pro 3EM-400

Environment

Ambient temperature: -10 to 50 °C
Humidity: 0 to 80 % RH
Max. altitude: 2000 m

Full device datasheet

Support

Frequently asked questions

Which Shelly device does this 400A transformer work with?
It works only with the Shelly Pro 3EM-400 energy meter; it is a measuring accessory and cannot operate on its own or with other meters.
How many transformers do I need for a three-phase installation?
Usually three units, one per phase, wired to the matching inputs of the Pro 3EM-400 for complete three-phase metering.
Do I need to disconnect the cable to fit the clamp?
No. The split-core design with screwless mounting lets you place the clamp around the existing conductor and secure it with cable ties on both sides.
What conductor size fits inside the clamp?
The conductor aperture is 35 mm and the maximum primary current is 400 A, which covers large-section cables in power panels.
Can I install this transformer myself?
Installation involves work inside the electrical panel and must be done by a qualified electrician; CasaSmart can plan the integration with the Pro 3EM-400.
In what environmental conditions can it operate?
It operates from -10 °C to 50 °C, at 0 % to 80 % RH and up to 2000 m altitude.

Same category

Questions about this product?

A CasaSmart manager calls you within 1–2 working hours and answers anything — compatibility, install, alternatives.

+373 60 944 922

Updated: 18 June 2026· reviewed by CasaSmart Expert Team