Overview
The LMZ3(D)-0.66 Current Transformer is a low-voltage, indoor-type cast resin insulated current transformer designed for 50/60 Hz power systems with a rated voltage up to 0.66 kV. Engineered for reliability and precision, it serves critical roles in energy metering, relay protection, and real-time current monitoring across industrial and commercial installations.
Built around a loop-type iron core with uniformly wound secondary windings and fully encapsulated in high-grade epoxy resin, the LMZ3(D)-0.66 delivers excellent magnetic efficiency, mechanical robustness, and environmental resistance. Its compact busbar-through design simplifies integration into switchgear and distribution panels while ensuring compliance with IEC 60044-1 and GB 1208-2006 standards for safe, accurate operation.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| Rated Voltage | 0.66 kV |
| Rated Frequency | 50/60 Hz |
| Accuracy Classes | 0.2, 0.5, 1, 3, 5P, 10P (model-dependent) |
| Primary Conductor Type | Busbar (through-hole) |
| Insulation Material | Epoxy resin (cast) |
| Installation Environment | Indoor only |
| Core Type | Loop-type iron core |
| Secondary Winding | Uniformly wound |
Model Designation
The model code “LMZ3(D)-0.66” follows standardized industry nomenclature to convey key design features:
- L = Current Transformer
- M = Busbar-type (window for primary conductor)
- Z = Cast Resin Insulated
- 3 = Design Series
- (D) = Optional variant (e.g., with terminal cover or specific accuracy configuration)
- 0.66 = Rated system voltage (0.66 kV)
Construction
The LMZ3(D)-0.66 features a toroidal (loop-type) iron core made from high-permeability electrical steel, ensuring minimal losses and high linearity across its operating range. The secondary winding is precisely and uniformly layered around the core to maintain phase accuracy and reduce leakage flux.
The entire assembly is fully encapsulated in flame-retardant epoxy resin via vacuum casting, providing excellent dielectric strength, moisture resistance, and mechanical durability. Terminals are clearly marked (P1/P2 for primary direction, S1/S2 for secondary output) and may include an optional protective cover in “(D)” variants for enhanced safety during maintenance or wiring.
Mounting is achieved through two standard holes on the base, allowing secure attachment to panels or busbar supports while maintaining necessary clearances for thermal and electrical safety.
Technical Parameters
Service Conditions
- Altitude: <=1000m
- Ambient Temp: -5 deg C to +40 deg C
- Relative Humidity: <=80% at 20 deg C
- Installation Environment: Indoor
- Rated Frequency: 50/60 Hz
- Rated Voltage: <=0.66 kV
Technical Data
| Model | Ratio | Accuracy | Burden | Thermal |
|---|---|---|---|---|
| LMZ3-0.66 | 100/5, 200/5, 400/5, etc. | 0.2, 0.5, 1, 3, 5P, 10P | 2.5 – 15 VA (varies by ratio/accuracy) | Compliant per IEC 60044-1 |
| LMZ3D-0.66 | 100/5, 200/5, 400/5, etc. | 0.2, 0.5, 1, 3, 5P, 10P | 2.5 – 15 VA (varies by ratio/accuracy) | Compliant per IEC 60044-1 |
Installation & Wiring
Installation Diagram
Install the LMZ3(D)-0.66 by passing a single primary busbar through the central window. Ensure the P1 marking faces the power source to maintain correct polarity. Secure the unit using the two mounting holes on the base. Always connect the secondary terminals (S1/S2) to a compatible meter, relay, or shorting linkânever leave open-circuited.
Selection & FAQs
Selection Guide
- Select the required primary/secondary ratio from the load, metering range, and protection study.
- Choose metering class 0.2, 0.5, 1, or 3, or specify 5P/10P for protection duty.
- Calculate total secondary burden and select an available 2.5VA–15VA configuration.
- Confirm that the central window, busbar, base holes, and cabinet clearances match the approved drawing.
- Verify polarity, secondary grounding, terminal cover requirement, ambient limits, and shorting provision.
Frequently Asked Questions
Q1: Can this low-voltage CT be installed outdoors?
No, it is strictly designed for indoor installation. Service conditions require ambient temperatures between -5°C and +40°C with relative humidity ≤80%. Contact us for outdoor-rated alternatives.
Q2: Which accuracy classes are available for protection relays?
The 5P and 10P accuracy classes are suitable for protection applications. These models support rated burdens from 2.5 to 15 VA per IEC 60044-1. Specify your exact ratio and burden requirements.
Q3: How does this current transformer handle short-circuit currents?
Thermal and dynamic short-circuit performance is fully compliant with IEC 60044-1 standards. The cast resin insulation ensures robust mechanical stability under fault conditions. Request the specific thermal current factor for your ratio.
Q4: What primary current ratios can be customized?
Standard ratios include 100/5, 200/5, and 400/5, but custom ratios are available subject to factory confirmation. Lead times vary based on specific project requirements.
Q5: Are factory test reports provided before shipment?
Yes, routine tests are conducted per IEC 60044-1 prior to dispatch. Standard test reports are included, while specific third-party certification is subject to confirmation. Indicate your documentation requirements during the inquiry.
Q6: When should I specify a 0.2 accuracy class?
The 0.2 class is required for high-precision revenue billing and critical energy metering. It ensures strict accuracy limits across the specified burden range of 2.5 to 15 VA.
Q7: Why choose cast resin insulation for indoor panels?
Cast resin provides excellent mechanical strength and moisture resistance for indoor environments up to 80% relative humidity. It ensures reliable operation for 0.66 kV systems without requiring additional protective enclosures. Request the technical datasheet for installation clearances.