High Accuracy Current Transformer For Industrial Energy Meter And Switchgear

This toroidal current transformer is a feed through sensing component used to
measure alternating current in industrial power equipment. The conductor being
measured passes through the centre window of the core and acts as a single turn
primary. The secondary winding, wound around the toroidal core, produces a
small, accurately scaled output current that is proportional to the current
flowing in that conductor. The measuring circuit therefore reads a large line
current safely, without any electrical connection to the line itself.

Galvanic isolation is the central function. The measuring electronics, the
microcontroller and ultimately the operator are separated from the high voltage
power circuit by the insulation of the core assembly rather than by a resistive
shunt sitting in the current path. This eliminates the ground reference problem
that a shunt creates, removes the power dissipation a shunt would generate at
high current, and allows the same sensing topology to be used on high voltage
lines where a direct connection would not be permissible.

The core is a closed toroid, which gives a uniform magnetic path with no air
gap and therefore high coupling between the primary conductor and the secondary
winding. This is what produces the low ratio error and low phase displacement
required for revenue grade metering and for protection relays that must
discriminate correctly during a fault. The assembly is tape wrapped and
insulated, and terminated with flexible lead wires with identification markers
for correct polarity installation.

The product is manufactured to order. Turns ratio, rated primary current,
accuracy class, window diameter, core material, output format, lead length and
lead marking are all defined against the customer specification.

Note: turns ratio, rated current, accuracy class, core material and dimensions
are defined per application. Approval drawings and samples are issued for your
confirmation before mass production.

• Closed toroidal magnetic path. A gapless toroid gives uniform flux distribution
  and tight coupling between the primary conductor and the secondary winding.
  This is the physical basis for low ratio error and low phase displacement, and
  it is why a toroidal construction is used wherever measurement accuracy has
  commercial or safety consequences.
• Core material matched to the accuracy target. Nanocrystalline and permalloy
  cores offer very high permeability and low error at small primary currents,
  which matters for metering that must stay accurate at light load. Silicon steel
  is the economical choice where the accuracy requirement is moderate and the
  current is high. We select against your class requirement rather than offering
  a single compromise.
• True galvanic isolation. The measuring side is separated from the power circuit
  by the insulation system, tested at high potential. There is no shunt in the
  current path, so there is no added power loss and no shared ground reference
  between the power stage and the control electronics.
• Wide linear range. The transformer maintains its specified accuracy from light
  load through to well above rated current, which allows one part to cover both
  normal metering and overload observation without a second sensing channel.
• Feed through installation. The conductor simply passes through the window, so
  the power circuit does not have to be broken to install the sensor. On a
  retrofit this reduces installation labour and eliminates the risk of a poorly
  made joint in the main current path.
• Flexible lead termination with identification. Marked leads allow correct
  polarity installation on the production line, which prevents the sign inversion
  error that otherwise appears only during final functional test.
• Compact form factor. The toroidal geometry gives a high performance to volume
  ratio, allowing the sensor to fit inside crowded meter housings, breaker
  enclosures and inverter cabinets.

• Industrial energy meters and sub metering systems
• Power monitoring and power quality analysis equipment
• Switchgear, distribution boards and protection relays
• Motor protection and motor control centres
• Solar inverters and energy storage system current sensing
• Uninterruptible power supplies and industrial backup power
• Electric vehicle charging infrastructure current measurement
• Building energy management and industrial load monitoring
• Overcurrent, earth fault and leakage current detection circuits
• Industrial automation systems requiring closed loop current feedback
• Test and measurement instrumentation

Typical functions include revenue grade energy measurement, real time load
monitoring, overcurrent trip sensing, phase balance verification on three phase
systems, and closed loop current feedback in converter control.

• Established in 2000, with 26 years of continuous experience in magnetic
  components and power solutions for industrial control and power electronics.
• A 10,000 square metre self owned factory with 8 complete production lines,
  which keeps capacity, process control and delivery schedule in house rather
  than subcontracted.
• Toroidal core winding is a core in house process, supported by a 20 person
  R&D team and a 20 person quality control team covering incoming material and
  outgoing product inspection.
• Certified management system: ISO 9001 for quality and ISO 14001 for
  environment. Products comply with RoHS and REACH, with CE, CB, UL and cUL
  coverage across the product range.
• Annual export value of 42 million USD, serving North America, Northern
  Europe, South America and Southeast Asia, including established industrial
  equipment brands.
• An 11 person export team providing direct technical communication in English,
  so engineering questions are resolved without a trading company in between.

• Accuracy defined by your class requirement. Core material, turns ratio and
  burden are engineered against the class you have to meet, not against a
  catalogue average.
• Stable performance across temperature. Material selection and impregnation
  keep ratio error and phase displacement within specification across the rated
  temperature range, which protects long term metering credibility.
• Consistent unit to unit output. Controlled winding tooling and electrical
  testing keep every piece inside the tolerance window, so your calibration
  routine does not have to compensate for supplier spread.
• No power loss in the measured circuit. Unlike a shunt, the transformer does
  not dissipate heat proportional to load current, which matters in sealed
  enclosures and at high current.
• Designed to your mechanical envelope. Window diameter, overall height, lead
  length and mounting arrangement are adapted to your existing housing.
• Free electrical design service. Send the rated current, accuracy class and
  burden and we will propose ratio, core and construction, then confirm with
  samples.