CT 200A/40mA
The CT 200A/40mA is the official current transformer kit from Solax Power for the M3-40 meter. With a 200A/40mA ratio, it extends the measurement capacity up to 200 Amps for commercial three-phase photovoltaic systems. Essential for export control and zero grid feed-in when grid currents exceed the 80A limit of direct connection.
The CT 200A/40mA is the official Solax Power current transformer (CT) for the M3-40 meter, with a transformation ratio of 200A/40mA. It allows you to extend the measurement capacity of the smart meter up to 200 Amps, covering medium-large size three-phase photovoltaic systems where the grid current exceeds the 80A limit of direct insertion.
What is the CT 200A/40mA used for?
Solax energy meters with direct insertion (DDSU666-D, DTSU666-D) measure currents up to 80A without external CTs. When the grid current exceeds 80A — in three-phase systems of over approximately 50 kW — it is necessary to pair the meter with external current transformers. The CT 200A/40mA is specifically calibrated for the Solax M3-40 meter: it pairs a primary current of 200A with a secondary signal of 40mA, compatible with the CT input ports of the M3-40 meter.
Technical specifications CT 200A/40mA
| Nominal primary current | 200 A |
| Secondary current | 40 mA |
| Transformation ratio | 200A / 40mA |
| Compatible meter | Solax M3-40 |
| Installation type | Clamp-on / pass-through hole on the phase conductor |
| Weight | 0.1 kg |
| Application | Grid current measurement for export control and zero feed-in on three-phase systems up to 200A |
Differences with the CTs included in the DTSU666-CT
The CT kit of the DTSU666-CT (100A/33.33mA) covers currents up to 200A on the system but with a different ratio, optimized for the CT ports of the DTSU666 meter. The CT 200A/40mA is instead calibrated for the Solax M3-40 meter with a 40mA input. The two types are not interchangeable: always use the correct CT for the supplied meter, respecting the transformation ratio indicated by the manufacturer.
What is included in the supply?
- Solax Power CT Kit 200A/40mA for M3-40 meter
Frequently Asked Questions
Is the CT 200A/40mA compatible with Solax meters other than the M3-40?
No. The CT 200A/40mA is specifically calibrated for the Solax M3-40 meter. The CT port of the M3-40 meter is designed to receive a secondary signal of 40mA: using CTs with different ratios (e.g. 100A/33.33mA from the DTSU666-CT) would cause measurement errors. For DTSU666-CT meters, use the dedicated CT kit included with the product or the specific 100A/33.33mA CT.
Does the CT 200A/40mA enable zero feed-in to the grid?
Yes, indirectly. The CT 200A/40mA extends the measurement capacity of the M3-40 meter up to 200A, allowing the meter to transmit real-time grid flow data to the Solax inverter. The inverter uses this data to activate export control and the zero feed-in function, just like with the CTs of the DTSU666-CT meters.
Does the kit include one CT per phase or just one?
The CT 200A/40mA kit is supplied as a complete set for the three-phase M3-40 meter, including the CTs required for three-phase measurement. For a three-phase system with measurement on all three phases, 3 CTs are required (one for each phase L1, L2, L3). Check the kit contents at the time of purchase; for single-phase meters, only one CT is needed.
When is the CT 200A/40mA needed instead of direct insertion?
Direct insertion of Solax meters covers currents up to 80A (approximately equivalent to three-phase systems up to about 55 kW at 400V). Beyond this threshold, it is necessary to pair the meter with external CTs. The CT 200A/40mA extends coverage up to 200A, suitable for commercial three-phase systems up to about 138 kW at 400V. For currents above 200A, higher capacity CTs are required (e.g. Chint CT-600A for systems with 5A CT input).
How is the CT 200A/40mA installed on the grid line?
The CT 200A/40mA is installed as a clamp (or pass-through hole, depending on the model) on the phase conductor at the grid connection point, without interrupting the circuit. The secondary signal (40mA) is connected to the CT port of the M3-40 meter via the supplied cable. The orientation of the CT relative to the direction of flow must follow the manufacturer's instructions (arrow towards the load or towards the grid, according to the manual). Installation must be carried out by a qualified electrician.
