Tuesday, April 23, 2024

Smart Shunt Series Uses Isolated Smart Current Measurement Technology

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Reinforced isolated high-power shunt module with amplified analogue output suitable for use in high-power applications in harsh conditions

Presenting a smart shunt SSA that incorporates a low-impedance manganese shunt resistance, a high-precision insulated amplifier and an isolated DC-DC converter.

The SSA includes an Isolated Smart Current Measurement Technology that consists of four current ratings: 100A, 250A, 500A and 1000A, making them suitable for use in high-power applications in harsh conditions such as high-temperature levels, heavy vibrations and electromagnetic interference (EMI). They are therefore ideal for use in electric vehicle (EV) and hybrid-electric vehicle (HEV) traction inverters, AC-DC converters, uninterruptible power supplies, renewable energy generation sites and smart grid infrastructure.

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Being immune to magnetic fields, the SSA can be freely positioned without the need for additional shielding, which allows more flexibility during development. 

These next-generation current sensing modules combine the attributes of conventional passive shunt resistors with Hall Effect current sensors. Each featuring a built-in precision amplifier, they offer reinforced electrical isolation (up to 1500VDC), along with being stable and accurate. Shunt-based systems are generally easier to implement because they are more linear and offer higher current measurement accuracy than Hall-based methods.

The new SSA devices feature: 

  • 1500 VDC/1000 VAC RMS reinforced isolation
  • ± 0.1% initial sensing accuracy
  • ± 0.1% linearity over the current range
  • Unipolar power supply
  • Differential analogue output 
  • 300kHz bandwidth. 

The series offers a differential output and can be connected directly to most MCUs.

Physical construction

With less susceptibility to temperature drift, the need for routine calibration can be eliminated. The SSA also has a rapid response time of less than 1.5μs. The amplified analogue output and integrated protection enable the current sensors to be placed on either the high or low side of a circuit, thereby enabling easy integration. Physical construction consists of a power bus bar with an isolated sensor housing encased around the centre of the bar. A JST JWPF series four-pin connector provides the interface to (1) power, (2) ground, (3) +Vin and (4) –Vin for the encapsulated sensor. The corresponding mating connector is JST type J04R-JWPF-VSLE-S (housing) and SWPR-001T-P025 (contact).

The differential output effectively negates the Thermo-EMK and eliminates all associated deviations that arise due to a temperature gradient above the block. Unlike other shunt solutions, the fully UL94-V0 encapsulated block provides enhanced isolation of 1500VDc (1000 VACeff), which allows it to be mounted in inverters on the high-side, although the installation on the low-side is recommended as best practice.

Power dissipation

Since the SSA contains an amplifier, the resistance value is extremely low, because the detected voltage is multiplied internally. Therefore, the power dissipation for measuring currents up to 1000 A is in the range of 5 to 20 W. The robust module includes an AEC-Q100 certified insulated amplifier from Texas Instruments and is therefore also suitable for the strict automotive applications that must cover the extended operating temperature range from -40 to 125 degrees Celsius.

The insulated amplifier offers a differential output with several advantages. If a single-ended signal is required, then this can be provided with a simple operational amplifier circuit (OPV). The differential output of the isolated amplifier is often converted into a single-ended analogue output with an OPV-based circuit. This circuit can also implement a low-pass filter to further reduce the signal bandwidth to the desired bandwidth, thereby improving the noise performance of the system.

Optional Mounting Hardware and Cable Assembly

For ease of mounting, an optional mounting fixture, the SSA-BASE, is available for models SSA-100 thru SSA-500. It is constructed of UL 94-V0 rated materials and uses 5/16-18 stainless steel hardware. An optional connector cable assembly, the SSA-CABLE-1M, is also available. The 1-meter standard cable is compatible with all SSA models.

The device by Rideon is now available from New Yorker Electronics.


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