Milesight CT303 Smart Current Transformer

Milesight CT303 / CT305 / CT310 Smart Current Transformer

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Where it sits in the stack

Price range: £101.75 through £246.90 ex VAT (£122.10 – £296.28 inc. VAT)

The Milesight CT303 is a self-powered LoRaWAN three-phase clamp-on current transformer reporting RMS current and accumulated consumption per phase. Its decisive figure is the rated primary current: 300 Arms per CT, through a Ф24.2 mm wire hole. Use it for distribution board and sub-metering energy monitoring in buildings; the clamps fit live conductors without de-energising.

Rated primary current (per CT)300 Arms per CT (CT303), three phases detected simultaneously

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Questions about this product? Call our UK team: 023 9223 3611

Solutions this product serves

Energy & Net Zero

Overview
Specifications

Description

DATASHEET

CT3xx is a LoRaWAN® Smart Current Transformer for monitoring energy consumption and analyzing usage remotely.

CT3xx provides multiple current options to suit energy monitoring and supports sending threshold alarms. Its compact size enables quick and safe installation in any indoor space without de-energizing facilities, thereby simplifying the installation and saving costs.

Compliant with Milesight LoRaWAN® gateway and Milesight Development Platform solution, CT3xx can be conveniently monitored via webpage remotely.

CT3xx is widely used for energy monitoring in smart buildings, machine failure detection and
prevention, etc.

• Features
• Report the RMS current and accumulated current data by minutes
• High measuring accuracy with a sampling frequency of up to 3.3 kHz
• Self-powered, free from batteries or external wires
• Utilize a sampling rate of up to 1s for real-time monitoring and quick alarm response
• Non-invasive clamp design ensures easy and safe installation without the need for power
de-energizing
• Equipped with LED indicator to indicate working status and alarms
• Support external wire temperature sensor for cable temperature measurement
• Enable simultaneous detection of three phases with a significantly wide optional detection
range of 300A, 500A or 1000A
• Compliant with standard LoRaWAN® gateways and network servers
• Compliant with Milesight Development Platform
• Support Firmware Update Over the Air (FUOTA) via Milesight Development Platform

Additional information

Weight	0.29 kg

Milesight CT303 / CT305 / CT310 Smart Current Transformer specifications

Rated primary current (per CT)	300 Arms (CT303)
Rated secondary current	150 mArms
Phases	Simultaneous detection of three phases
Minimum reporting current	3 Arms (1 min interval); 2.5 Arms (10 min interval), when powered by the testing conductor
Detection parameter	RMS current
Accuracy	±1%
Resolution	1 mA
Sampling frequency	3.3 kHz
Working frequency	50~60 Hz
Temperature sensor	1 × NTC sensor, measuring range -20°C ~ 100°C, accuracy ±1%
Protocol / mode	LoRaWAN®; OTAA/ABP Class A
Frequency	CN470/IN865/RU864/EU868/US915/AU915/KR920/AS923-1&2&3&4
Tx power / sensitivity	16 dBm (868 MHz) / 20 dBm (915 MHz) / 19 dBm (470 MHz); -137 dBm
Antenna connector	1 × 50 Ω SMA connector (centre pin: SMA female)
Power supply	Induced current power supply (phase A wire only), or 5 V via USB Type-C
Insulation voltage	3 kVac (r.m.s.) (1 mA/1 min)
Wire hole	Ф24.2 mm (CT303)
Clamp dimensions & weight	56.5 × 36.5 × 68.5 mm; 250 g per CT clamp (CT303)
Transceiver dimensions & weight	38 × 34.5 × 16 mm; 13.05 g
Operating temperature	Transceiver -20°C~70°C; CT clamp -40°C~55°C
Ingress protection	IP30
Approvals	CE, FCC, UL508

Specifications taken from the manufacturer datasheet.

Which version do I need?

The CT3xx family differs by rated primary current per CT: CT303 300 Arms (Ф24.2 mm hole), CT305 500 Arms (Ф36.5 mm), CT310 1000 Arms (Ф51 mm). Frequency bands include EU868, which UK and EU LoRaWAN uses and which this -868M part is supplied on, at 16 dBm.

Typical applications for the Milesight CT303 / CT305 / CT310 Smart Current Transformer

Three-phase energy monitoring in smart buildings
Distribution board sub-metering
Machine failure detection and prevention
Cable temperature monitoring via the NTC input
Threshold and overrange current alarms

Buying guides for this product

Energy Monitoring Sensors →

Frequency band

Supplied on EU868, the LoRaWAN band used in the UK and across Europe. That is the default and you do not need to ask for it — the -868M in the part number is the EU868 build.

The same Milesight CT303 / CT305 / CT310 Smart Current Transformer unit also covers IN865 and RU864. Those bands share the 863–870 MHz radio with EU868, so one device can be set to any of them in its own configuration — no different part number needed.

CN470, US915, AU915, KR920 and AS923 are a different radio and therefore a different build. Milesight makes them and we can order them: tell us where the devices are being deployed and we will confirm the part number, price and lead time.

Not sure which band applies where? The Things Network publishes the LoRaWAN frequency plan for every country.

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Milesight CT303 / CT305 / CT310 Smart Current Transformer — frequently asked questions

What is the maximum current per phase?

300 Arms per CT on the CT303. Within the same family the CT305 is rated 500 Arms per CT and the CT310 1000 Arms per CT, with wire holes of Ф36.5 mm and Ф51 mm respectively.

Does one unit cover all three phases?

Yes. The CT3xx enables simultaneous detection of three phases. On the CT303 each clamp has a Ф24.2 mm wire hole and weighs 250 g.

What is the lowest current it will report?

When self-powered from the conductor it reports from 3 Arms at a 1-minute interval or 2.5 Arms at a 10-minute interval. Lower currents require USB power.

How is it powered?

By induced current from the measured conductor, which the datasheet notes can only be the phase A wire, or with 5 V through the USB Type-C port. No battery is used.

What are the temperature limits?

The transceiver operates from -20°C to 70°C and the CT clamps from -40°C to 55°C, at ≤95% RH non-condensing, with IP30 ingress protection.

How much does the Milesight CT303 / CT305 / CT310 Smart Current Transformer cost in the UK?

The Milesight CT303 / CT305 / CT310 Smart Current Transformer starts at £101.75 ex VAT from Indiott, with the exact figure depending on the variant you choose. Indiott is a UK distributor and invoices with VAT (PSI Technologies Ltd, VAT GB 730 2340 83). UK delivery is a flat £14.25 per order ex VAT, whatever the weight.

What is the lead time and delivery cost for the Milesight CT303 / CT305 / CT310 Smart Current Transformer?

The Milesight CT303 / CT305 / CT310 Smart Current Transformer is in stock and typically dispatched within 14 working days from the UK. UK delivery is a flat £14.25 per order ex VAT, whatever the weight or how many items you order. We ship to GB and the EU and provide a VAT invoice with every order.