china current transformer excitation polarity ratio tester factory: Specification, Ordering and Quality Notes
What This Product Is and Where It Fits
First-article tooling determines the baseline accuracy of every unit leaving the line.
The tester is a portable, microprocessor‑driven instrument that measures excitation current, polarity, and ratio of current transformers up to 5000 A primary. It combines a precision current source, a high‑resolution ADC, and a calibrated reference winding in a single enclosure. Typical users are utility maintenance crews, substation commissioning teams, and third‑party testing labs that need on‑site verification without a full laboratory setup.
- Substation commissioning – verify CT polarity before energisation
- Periodic maintenance – track excitation curve drift over service life
- Factory acceptance testing – confirm ratio error within IEC 61869‑2 class limits
- Portable field audits – battery operation up to 8 h per charge
The Problem Buyers Keep Paying For
The build method decides whether a batch drifts into costly re‑calibration cycles.
When the reference winding is wound on a low‑grade former, its inductance shifts with temperature, causing ratio error to wander beyond the 0.2 % class limit after a few hundred hours. Inadequate shielding on the ADC front‑end lets mains‑frequency noise couple into the excitation measurement, producing polarity flips that are only discovered during post‑installation audits. Both failure modes force the buyer to ship units back for factory recalibration, incurring freight, downtime, and warranty administration costs that far exceed the marginal price of a higher‑grade core and a guarded PCB layout.
Design Constraints Behind the Specification
Consistency is set at the forming stage of the magnetic core and the digital front‑end.
Core‑to‑Display Chain
The excitation current passes through a nanocrystalline core whose permeability is trimmed to ±0.5 % before encapsulation. A 24‑bit sigma‑delta ADC samples the secondary voltage at 48 kS/s, and a firmware‑locked digital filter rejects 50/60 Hz harmonics to 120 dB. Because the filter coefficients are burned into OTP memory at final test, no field firmware update can alter the measurement bandwidth – a deliberate lock that prevents accidental drift but also means any bandwidth change requires a new hardware spin.
Specification Range and Customisation Limits
| Parameter | Range | Typical Tolerance |
|---|---|---|
| Primary Current Rating | 5 A – 5000 A | ±0.2 % of reading |
| Excitation Voltage | 0 – 120 V rms | ±0.1 % FS |
| Polarity Detection | Automatic, LED indication | 100 % reliability at ≥10 % rated current |
| Operating Temperature | ‑20 °C to +55 °C | Spec drift ≤0.05 %/°C |
| Weight (incl. battery) | 3.2 kg – 4.1 kg | ±0.1 kg |
| Dimensions (W×H×D) | 260 mm × 180 mm × 95 mm | ±2 mm each axis |
| Test Scenario | Observed Failure | Spec Guard |
|---|---|---|
| High‑humidity substation (95 % RH) | Connector corrosion → intermittent polarity signal | IP67 sealed test leads, gold‑plated contacts |
| Extended battery operation (>6 h) | Voltage sag causes ADC reference drift | Low‑dropout regulator with 0.5 % line regulation |
| Vibration during transport (2 g RMS) | Core former micro‑cracks → permeability shift | Epoxy‑potted core, shock‑rated enclosure (IK08) |
What Can Be Customised and What Cannot
Customisable
- Front‑panel logo and colour scheme (screen‑print or laser‑etch)
- Language pack for on‑screen menus (up to 5 languages per order)
- Carry‑case foam insert geometry (to fit existing tool kits)
- Calibration certificate format (PDF, CSV, or proprietary XML)
Fixed
- Core material grade – nanocrystalline only, no ferrite option
- ADC resolution – 24‑bit locked, cannot be downgraded
- Measurement bandwidth – 10 Hz to 5 kHz fixed by firmware OTP
- Safety rating – IEC 61010‑1 CAT III 600 V, non‑negotiable
Requirements by Buyer Segment
- Utility Procurement – demands traceable calibration to national standards, 2‑year warranty, and batch‑level test reports; prefers bulk packaging in reusable crates.
- Private‑Label Distributor – needs white‑label firmware splash screen, custom packaging inserts, and a minimum order of 50 units to amortise tooling.
- OEM Integrator – requires RS‑485 Modbus RTU output with configurable register map, and a mechanical mounting pattern compatible with 19‑inch rack kits.
Ready to align the tester with your private‑label spec? Share your requirement sheet and we’ll return a tooling review within two business days.
Request a tooling review
