Overview
The RCT Indoor Current Transformer is a precision-engineered device designed for accurate current measurement in low-voltage electrical systems operating at 50/60 Hz with a rated voltage up to 0.66 kV. Built for reliability and consistency, it supports critical functions including energy metering, power monitoring, and relay protection in residential, commercial, and light industrial indoor installations.
Featuring a loop-type iron core and uniformly wound secondary winding, the RCT ensures stable magnetic performance and high measurement fidelity across its operational range. Its compact, lightweight housing includes a bottom-mounted plate and a central busbar aperture, enabling secure, space-efficient mounting in switchgear panels, distribution boards, and control cabinets.
Key Ratings Snapshot
| Item | Specification (per order / nameplate) |
|---|---|
| System voltage class | 0.66 kV or below (indoor low-voltage distribution applications) |
| Rated frequency | 50 Hz or 60 Hz |
| Rated secondary current | 5 A |
| Accuracy classes | 0.5, 1.0 (metering and protection cores) |
| Rated burden | 5 VA, 10 VA, 15 VA, 25 VA (per core/winding as specified) |
| Burden power factor | cosφ = 0.8 (lagging) unless otherwise specified |
| Insulation level | 0.5 kV / 3 kV (rated insulation voltage / withstand test voltage) |
| Applicable standards | GB/T 20840.8-2007 (Instrument Transformers – Part 8: Electronic Current Transformers); JB/T 5356-2002 (General Technical Requirements for Low-Voltage Current Transformers) |
| Core aperture variants | φ35, φ58, φ90, φ110 (for different primary conductor sections) |
Model Designation
Construction
The RCT transformer employs a high-permeability loop-type iron core that minimizes hysteresis and eddy current losses, ensuring excellent linearity and phase accuracy. The secondary winding is uniformly layered and impregnated with insulating resin for enhanced dielectric strength and long-term thermal stability.
All models feature robust thermoplastic housings rated for indoor use, with screw-type secondary terminals for secure connection to meters or relays. The bottom-mounted installation plate allows direct fixation to panel surfaces, while the smooth central aperture accommodates solid or stranded busbars without requiring disconnection during installation.
Technical Parameters
Service Conditions
- Working place: Indoor
- Ambient temperature: -5 deg C to 40 deg C
- Humidity: <=80%
- Altitude: <=1000 m
- Atmospheric conditions: No serious pollution
Technical Data
| Type
(Core Aperture) |
Current Ratio (A) |
Busbar
Section (mm) |
Purchase
Specification (mm) |
Straigh
through Turn Number |
Accuracy Class
Output (VA) |
Insulation
Level (kV) |
|
|---|---|---|---|---|---|---|---|
| 0.5 | 1.0 | ||||||
| φ35 | 15/5 | — | — | 10 | 5 | 10 | 0.5/3 |
| 20/5 | — | — | 5 | 5 | 10 | ||
| 30/5 | — | — | 5 | 5 | 10 | ||
| 40/5 | — | — | 3 | 5 | 10 | ||
| 50/5 | — | — | 2 | 5 | 10 | ||
| 75/5 | — | — | 2 | 5 | 10 | ||
| 100/5 | 30 × 10 | 1 | 1 | 5 | 10 | ||
| φ58 | 150/5 | 30 × 10 | 1 | 1 | 10 | 15 | 0.5/3 |
| 200/5 | 30 × 10 | 1 | 1 | 10 | 15 | ||
| 300/5 | 50 × 10 | 1 | 1 | 10 | 15 | ||
| 400/5 | 50 × 10 | 1 | 1 | 10 | 15 | ||
| φ90 | 500/5 | 50 × 10 | 60 × 10 | 1 | 15 | 25 | 0.5/3 |
| 600/5 | 50 × 10 | 60 × 10 | 1 | 15 | 25 | ||
| 800/5 | 80 × 10 | 60 × 10 | 1-2 | 15 | 25 | ||
| 1000/5 | 80 × 10 | 60 × 10 | 1-2 | 15 | 25 | ||
| φ110 | 1200/5 | 80 × 10 | 80 × 10 | 1-2 | 15 | 25 | 0.5/3 |
| 1500/5 | 100 × 10 | 80 × 10 | 1-2 | 15 | 25 | ||
| 2000/5 | 100 × 10 | 80 × 10 | 1-2 | 15 | 25 | ||
| 2500/5 | 100 × 10 | 80 × 10 | 1-2 | 15 | 25 | ||
| 3000/5 | 100 × 10 | 80 × 10 | 1-2 | 15 | 25 | ||
| 4000/5 | 100 × 10 | 80 × 10 | 1-2 | 15 | 25 | ||
Installation & Wiring
Installation Diagram
Mount the RCT transformer securely using the pre-drilled holes on the bottom plate. Pass the primary conductor straight through the central aperture, ensuring no sharp bends or mechanical stress near the transformer. Connect the secondary terminals to the metering or protection device using insulated copper wire rated for the specified burden.
Outline Dimensions
| Type | d (mm) | A (mm) | B (mm) | D (mm) | G (mm) | H (mm) | L (mm) |
|---|---|---|---|---|---|---|---|
| RCT-35 | 35 | 95 | 80 | 78 | 45 | 90 | 54 |
| RCT-58 | 58 | 110 | 88 | 100 | 45 | 113 | 56 |
| RCT-90 | 90 | 110 | 88 | 135 | 38 | 147 | 40 |
| RCT-110 | 110 | 110 | 88 | 163 | 38 | 177 | 40 |
Selection & FAQs
Selection Guide
- Select the 15/5A–4000/5A ratio from normal load, maximum current, and metering range.
- Choose a 35mm, 58mm, 90mm, or 110mm aperture by cable or busbar dimensions and clearance.
- Specify class 0.5 or 1.0 according to accuracy requirements and ratio availability.
- Calculate device and cable-loop burden and confirm the available 5VA–25VA output.
- Verify mounting plate dimensions, primary turns if required, polarity, grounding, and terminal access.
Frequently Asked Questions
Q1: What are the environmental limits for installing this indoor current transformer?
This indoor current transformer requires ambient temperatures between -5°C and 40°C, with humidity ≤80%. It is rated for altitudes up to 1000m without serious atmospheric pollution. Please contact us for installations outside these parameters.
Q2: Which accuracy class output should I select for standard metering applications?
Choose the 0.5 accuracy class for standard metering and 1.0 for general indication. Both classes support an output of 5 to 10 VA at a power factor of 0.8. Confirm your specific burden requirements during ordering.
Q3: How do I determine the correct core aperture and busbar section?
Select the φ35 or φ58 core aperture based on your primary conductor size. For the 100/5A and 150/5A ratios, the required busbar section is 30 × 10 mm. Provide your exact busbar dimensions to the factory for final verification.
Q4: Can the straight-through turn number be adjusted for lower primary current ratios?
Yes, the primary turns can be increased to achieve lower effective current ratios. For example, a 15/5A ratio requires 10 straight-through turns. Specify your required primary current and turn count for factory calibration.
Q5: What is the insulation level and are factory tests included before shipment?
The insulation level is rated at 0.5/3 kV. Standard factory routine tests are performed prior to shipment to ensure compliance. Please contact our sales team for detailed test reports and specific certification requirements.
Q6: Is this RCT current transformer suitable for outdoor switchgear applications?
No, this RCT model is specifically designed and manufactured for indoor switchgear and panel board applications. It lacks the weatherproofing required for outdoor environments. Request our outdoor-rated models if your project requires external installation.
Q7: What primary current ratios are available for the φ58 core aperture type?
The φ58 core aperture supports current ratios starting from 150/5A. Lower ratios like 15/5A up to 100/5A are available with the φ35 core type. Contact our engineering team for custom ratio configurations outside this standard range.