Overview
The JSGW-0.5 dry-type low-voltage potential transformer is an indoor three-phase five-leg voltage transformer engineered for precise voltage measurement, electric energy metering, and reliable relay protection in 50Hz AC power systems. It delivers stable, proportional secondary voltage signals to measuring instruments, energy meters, and protection relays, ensuring accurate system monitoring and control.
Built with a dry-type insulated structure and a three-phase five-leg magnetic core, the JSGW-0.5 includes both main and auxiliary secondary windings. This design enables standard phase-to-neutral voltage output as well as open-delta residual voltage monitoring, making it ideal for insulation supervision, abnormal voltage detection, and comprehensive protection schemes in indoor electrical installations.
Key Ratings Snapshot
| Parameter | Value |
|---|---|
| Rated frequency | 50 Hz |
| Voltage ratio (typical) | 380/sqrt(3) : 100/sqrt(3) : 100/3 V 500/sqrt(3) : 100/sqrt(3) : 100/3 V |
| Main secondary voltage | 100/sqrt(3) V |
| Auxiliary secondary voltage | 100/3 V |
| Accuracy classes | 0.5, 1, 3 |
| Rated output (VA) | 50 (0.5 class), 80 (1 class), 250 (3 class) |
| Maximum rated output | 340 VA |
| Insulation level | 0.5/3 kV |
| Core structure | Three-phase five-leg external iron core |
| Installation location | Indoor |
Model Designation
- J: Voltage transformer / potential transformer
- S: Three-phase structure
- G: Five-leg magnetic core
- W: Dry-type design
- 0.5: Voltage grade / product voltage class code
- F: Optional extended design code where applicable
Construction
The JSGW-0.5 features a robust dry-type insulated construction with no oil or liquid fill, making it safe and maintenance-free for indoor environments. Its three-phase five-leg magnetic core consists of three central limbs for primary voltage transformation and two outer return limbs that support the auxiliary winding for residual voltage output. This configuration ensures high magnetic balance and minimal zero-sequence error during normal and fault conditions.
All windings are vacuum-pressure impregnated with epoxy resin, providing excellent dielectric strength, thermal stability, and resistance to moisture and contamination. The compact mechanical design allows secure mounting inside switchgear, metering panels, and protection cabinets, with clearly marked terminals for primary, main secondary, and auxiliary secondary circuits.
Technical Parameters
Service Conditions
- Installation location: Indoor only
- Ambient temperature: -5 deg C to +40 deg C (standard)
- Relative humidity: <= 95% at 25 deg C
- Altitude: <= 1000 m above sea level
- Environment: Free from severe vibration, corrosive gases, explosive media, conductive dust, and heavy pollution
Technical Data
| Rated Voltage Ratio |
Frequency (Hz) |
Output 0.5 Class (VA) |
Output 1 Class (VA) |
Output 3 Class (VA) |
Max. Output (VA) |
Insulation Level (kV) |
|---|---|---|---|---|---|---|
| 380/sqrt(3) : 100/sqrt(3) : 100/3 | 50 | 50 | 80 | 250 | 340 | 0.5/3 |
| 500/sqrt(3) : 100/sqrt(3) : 100/3 | 50 | 50 | 80 | 250 | 340 | 0.5/3 |
Installation & Wiring
Installation Diagram
The JSGW-0.5 series is designed for fixed indoor installation within switchgear or metering cabinets. Primary terminals (A, B, C, 0), main secondary terminals (a, b, c, 0), and auxiliary secondary terminals (ad, xd) must be wired strictly according to the approved schematic diagram. Ensure correct polarity and terminal identification prior to energization.
Outline Dimensions
| Dimension | Value (mm) |
|---|---|
| Height | To be confirmed per approved drawing |
| Width | To be confirmed per approved drawing |
| Depth | To be confirmed per approved drawing |
| Mounting hole pattern | Per project-specific outline drawing |
| Terminal clearance | Sufficient for standard lugs and creepage requirements |
Selection & FAQs
Selection Guide
- Select the correct phase-to-neutral primary voltage. Choose 380/√3V or 500/√3V based on system line voltage and neutral connection.
- Define the main and auxiliary circuits separately. The main output is 100/√3V; the 100/3V auxiliary winding is for residual-voltage/open-delta-related monitoring according to the approved schematic.
- Choose the main accuracy burden. Use class 0.5 at 50VA, class 1 at 80VA or class 3 at 250VA, keeping actual connected burden within the selected rating.
- Do not treat 340VA as an accuracy output. It is the maximum output reference; confirm total thermal loading and the separately allowable auxiliary burden.
- Approve the complete three-phase connection. Verify A/B/C/0, a/b/c/0 and ad/xd polarity, neutral grounding, fuses, phase sequence, insulation, dimensions and ventilation.
Frequently Asked Questions
Q1: Is outdoor installation supported for this low voltage transformer?
No, it is strictly for indoor installation only. The environment must be free from severe vibration, corrosive gases, and conductive dust. Confirm specific site conditions with our engineers.
Q2: Which voltage ratio fits a 380V three-phase system?
The 380/√3 : 100/√3 : 100/3 ratio is designed for 380V systems. A 500/√3 option is also available for 500V networks. Contact us to verify your exact system requirements.
Q3: What is the maximum output capacity for 0.5 class?
The 0.5 accuracy class supports up to 50 VA output. For higher burdens, 1 class (80 VA) and 3 class (250 VA) are available, with a maximum output of 340 VA.
Q4: Can we customize the installation dimensions and special ratios?
Yes, special voltage ratios, output ratings, and dimensions can be customized. These modifications are subject to technical agreement before ordering. Please contact our sales team for details.
Q5: When can we expect delivery for custom ratio orders?
Standard lead times apply to regular stock items. However, exact delivery schedules for custom ratios and dimensions are subject to confirmation. Contact our sales team for current production schedules.
Q6: Where is this three-phase five-leg transformer typically applied?
It is ideal for indoor low-voltage power distribution and metering in 50Hz systems. The five-leg core design ensures reliable voltage measurement and insulation monitoring.