Overview
The LMZ and LMZJ1-0.5 series are precision low-voltage current transformers designed for accurate current measurement, energy metering, and relay protection in AC power systems up to 0.66 kV. These through-core busbar type CTs deliver galvanically isolated secondary signals proportional to primary current, ensuring reliable operation in commercial and industrial distribution networks.
Built with toroidal cold-rolled oriented silicon steel cores and cast resin insulation, these transformers offer excellent electrical performance, moisture resistance, and long-term stability under standard indoor service conditions.
Key Ratings Snapshot
| Item | Specification |
|---|---|
| System voltage class | 0.66 kV |
| Rated frequency | 50 Hz (60 Hz on request) |
| Rated secondary current | 5 A |
| Accuracy classes | 0.2, 0.5, 0.2S, 0.5S |
| Primary current range | 5 A to 5000 A |
| Continuous operation | 110% of rated primary current |
| Dielectric withstand | 3 kV, 1 min (secondary to ground) |
| Burden power factor | cos phi = 0.8 (lagging) |
| Rated burden | As specified per core (VA) |
| Insulation | Cast resin (unsaturated resin) |
Model Designation
- L: Current transformer (CT)
- M: Busbar type (through-core construction)
- Z: Cast-resin insulated structure
- J: Extended capacity (LMZJ1 only)
- 1: Design code / iteration (LMZJ1 only)
- 0.5: Voltage class (kV)
Construction
The LMZ/LMZJ1-0.5 series features a through-core busbar design with fixed baseplate mounting, optimized for stable installation in low-voltage switchgear and distribution panels. The core is made from high-permeability cold-rolled oriented silicon steel, wound into a toroidal shape to minimize losses and ensure linear response across the operating range.
Encapsulated in cast unsaturated resin insulation, the unit provides superior resistance to moisture, contamination, thermal aging, and mechanical stress. This construction ensures consistent dielectric strength, long service life, and compliance with safety clearances required for indoor 0.66 kV applications.
Technical Parameters
Service Conditions
- Installation environment: Indoor only
- Altitude: <= 1000 m above sea level
- Ambient temperature: -5 deg C to +40 deg C
- Relative humidity: <= 80%
- Environmental conditions: Free from corrosive gases, severe contamination, explosive or flammable substances
Technical Data
| Type | Rated
Primary |
Rated
Secondary |
Rated Secondary
Output (VA) |
Primary Ampere-Turns |
||||
|---|---|---|---|---|---|---|---|---|
| 0.2 | 0.5 | 0.5S | 1 | 10P5 | ||||
| LMZ1-0.5 | 5, 10, 20, 100 | 5 / 1 | 5 | 5 | 5 | 7.5 | – | 100 |
| 15, 30, 75, 150 | 150 | |||||||
| 40, 200 | 200 | |||||||
| 300 | 300 | |||||||
| 400 | 400 | |||||||
| LMZJ1-0.5 | 5, 10, 15, 20, 30, 50,
75, 100, 150, 300 |
5 | 10 | 15 | 300 | |||
| 400, 200, 400 | 400 | |||||||
| 500, 600 | 10 | 500, 600 | ||||||
| 800 | 800 | |||||||
| 1000, 1200, 1500 | 15 | 20 | 10 | 30 | 10 | 1000, 1200, 1500 | ||
| 2000, 3000 | 2000, 3000 | |||||||
Installation & Wiring
Installation Diagram
The transformer must be securely mounted using the baseplate fixing holes. The primary busbar passes through the central aperture; for ratios requiring multiple turns, the conductor loops through the core as indicated in the technical data. Maintain adequate clearance for safety, heat dissipation, and maintenance access. Connect secondary terminals to metering or protection devices using properly sized conductors to minimize burden.
Outline Dimensions
| Type | Rated Primary
Current (A) |
H | h | D | d | B |
|---|---|---|---|---|---|---|
| LMZ1-0.5 | 5, 10, 20, 100 | 112 | 65 | 83 | 25 | 43 |
| 15, 30, 75, 150, 200 | 30 | 45 | ||||
| 300 | 121 | 71 | 90 | 35 | 43 | |
| 400 | 45 | 45 | ||||
| LMZJ1-0.5 | 5, 10, 20, 30, 50,
75, 100, 150, 300 |
35 | 43 | |||
| 400, 500, 600 | 45 | 45 |
Selection & FAQs
Selection Guide
- Select LMZ1 or LMZJ1 and the 5A–3000A ratio from load, metering, and protection requirements.
- Choose the permitted 1A or 5A secondary and accuracy class for the selected model.
- Calculate total secondary burden and select an available 5VA–30VA output.
- Confirm aperture, required primary turns, busbar dimensions, base mounting, and cabinet clearance.
- Verify polarity, secondary grounding, terminal access, ambient limits, and shorting provision.
Frequently Asked Questions
Q1: Can this cast resin CT be installed outdoors?
No, it is strictly for indoor installation. The service conditions require an environment free from corrosive gases and severe contamination. Contact us for outdoor-rated alternatives.
Q2: Which accuracy class is suitable for energy metering?
The 0.5S accuracy class is ideal for precise energy metering. It provides high accuracy across a wide current range. Confirm your specific burden requirements with our engineering team.
Q3: What is the maximum rated primary current available?
The LMZJ1-0.5 model supports up to 500A rated primary current. Standard secondary currents are 5A or 1A. Please specify your exact primary current ratio during inquiry.
Q4: Can we request specific factory tests before shipment?
Yes, standard routine tests are performed, but special tests are subject to confirmation. Specify your required testing protocols in your purchase order for factory verification.
Q5: How long is the standard delivery time for bulk orders?
Lead times vary based on order quantity and current production schedules. Delivery time is subject to confirmation upon order placement. Contact our sales team for an exact schedule.
Q6: What applications suit this 0.5kV cast resin CT?
These indoor current transformers are applied in 0.5kV low voltage distribution panels and switchgear. The cast resin design provides reliable insulation for standard industrial power measurement.
Q7: Are these transformers suitable for high-altitude installations?
They are designed for altitudes up to 1000 meters above sea level. For installations exceeding this limit, derating factors apply. Please consult our technical department for high-altitude specifications.
Q8: What insulation material is used in this LMZ series?
The LMZ series utilizes indoor cast resin insulation. This solid dielectric material ensures high mechanical strength and reliable performance in 0.5kV low voltage applications.