Project Code: APM ETU 2019 ADI’S ETU SOLUTION FOR LOW ......the ETU harvests power from the sensor...
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Visit analog.com Project Code: APM_ETU_2019 ADI’S ETU SOLUTION FOR LOW VOLTAGE CIRCUIT BREAKERS What Is the ETU of a Low Voltage Circuit Breaker? A low voltage circuit breaker is an industrial and residential circuit breaker of less than 1500 V, including architecture circuit breakers (ACBs), molded case circuit breakers (MCCBs), microcircuit breakers (MCBs), residual current protective devices (RCPDs), and more. An electronic trip unit (ETU) is a programmable device that measures and times current flowing through the circuit breaker and initiates a trip signal when appropriate. As modern low voltage power distribution systems require more communication/intelligent function to realize higher level system features (for example, zone interlocking), the microprocessor-based electronic controller unit is becoming more and more popular in the low voltage switchgear/breaker system. Existing Solutions and Design Challenges Almost all of the existing solutions on the market are based on discrete components, which usually introduces the following design challenges: Smaller PCB Size and Form-Factor Design Circuit breaker frame sizes are becoming smaller and smaller from one generation to the next. As a result, the PCB hardware designer must do more form-factor optimization to meet mechanical size requirements, which usually leads to multiple PCB boards with industry interconnectors in between and more EMC challenges. Production Yield Rate One significant design challenge for mass production is to increase the yield rate on the manufacturer’s side. Clearly, it’s harder to control the yield rate for a PCB with 100+ discrete components rather than a PCB based on a fully pretested integrated IC. System Cost Cost is always a topic for high volume electronic design. From a system point-of-view, an application specific standard product (ASSP) can reduce the system cost based on the fact that it can reduce the overall PCB size/number, the demand for interconnection between the PCBs, the system level testing cost, and the increase in manufacture yield rate. Power Supply Design A typical ETU system harvests its power from the current transformer (CT) sensor. In some special testing cases, the ETU will start to operate as soon as the overcurrent condition begins. In such a case, the complete PCB power-on sequencer needs to be precisely controlled. Sometimes, due to component variation, a discrete solution has trouble maintaining performance over the year and temperature range. On the other hand, as the ETU harvests power from the sensor itself, a system-level low power becomes critical. Robustness A typical installation environment of a low voltage circuit breaker will be located with the low voltage grid distribution switchgear box. The environment is a typical industry level installation and the ETU needs to be reliable through different electrical shocks, mechanical shocks, and temperature shocks over the entire lifecycle. An ASSP IC designed for such an application needs a special protection scheme in order to guarantee a system level robustness. Single Hardware Platform to Suit Different Modules One ETU PCB will typically need to be suitable for a series of breakers with different rated currents, meaning that the hardware needs to be easily reconfigurable. Advanced Accuracy Requirement Some high end ETUs need to integrate metering as well. The hardware needs to be designed for a dual coil current transformer (power coil and signal coil).
Transcript of Project Code: APM ETU 2019 ADI’S ETU SOLUTION FOR LOW ......the ETU harvests power from the sensor...
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Project Code: APM_ETU_2019
ADI’S ETU SOLUTION FOR LOW VOLTAGE CIRCUIT BREAKERS
What Is the ETU of a Low Voltage Circuit Breaker?A low voltage circuit breaker is an industrial and residential circuit breaker of less than 1500 V, including architecture circuit breakers (ACBs), molded case circuit breakers (MCCBs), microcircuit breakers (MCBs), residual current protective devices (RCPDs), and more.
An electronic trip unit (ETU) is a programmable device that measures and times current flowing through the circuit breaker and initiates a trip signal when appropriate. As modern low voltage power distribution systems require more communication/intelligent function to realize higher level system features (for example, zone interlocking), the microprocessor-based electronic controller unit is becoming more and more popular in the low voltage switchgear/breaker system.
Existing Solutions and Design ChallengesAlmost all of the existing solutions on the market are based on discrete components, which usually introduces the following design challenges:
Smaller PCB Size and Form-Factor DesignCircuit breaker frame sizes are becoming smaller and smaller from one generation to the next. As a result, the PCB hardware designer must do more form-factor optimization to meet mechanical size requirements, which usually leads to multiple PCB boards with industry interconnectors in between and more EMC challenges.
Production Yield RateOne significant design challenge for mass production is to increase the yield rate on the manufacturer’s side. Clearly, it’s harder to control the yield rate for a PCB with 100+ discrete components rather than a PCB based on a fully pretested integrated IC.
System CostCost is always a topic for high volume electronic design. From a system point-of-view, an application specific standard product (ASSP) can reduce
the system cost based on the fact that it can reduce the overall PCB size/number, the demand for interconnection between the PCBs, the system level testing cost, and the increase in manufacture yield rate.
Power Supply DesignA typical ETU system harvests its power from the current transformer (CT) sensor. In some special testing cases, the ETU will start to operate as soon as the overcurrent condition begins. In such a case, the complete PCB power-on sequencer needs to be precisely controlled. Sometimes, due to component variation, a discrete solution has trouble maintaining performance over the year and temperature range. On the other hand, as the ETU harvests power from the sensor itself, a system-level low power becomes critical.
RobustnessA typical installation environment of a low voltage circuit breaker will be located with the low voltage grid distribution switchgear box. The environment is a typical industry level installation and the ETU needs to be reliable through different electrical shocks, mechanical shocks, and temperature shocks over the entire lifecycle. An ASSP IC designed for such an application needs a special protection scheme in order to guarantee a system level robustness.
Single Hardware Platform to Suit Different ModulesOne ETU PCB will typically need to be suitable for a series of breakers with different rated currents, meaning that the hardware needs to be easily reconfigurable.
Advanced Accuracy RequirementSome high end ETUs need to integrate metering as well. The hardware needs to be designed for a dual coil current transformer (power coil and signal coil).
2 ADI’s ETU Solution for Low Voltage Circuit Breakers
Solutions from ADIKey Product and ADI Solution Value Preposition
ADP2450
ADP2450 from Analog Devices is an ASSP specially designed for low voltage circuit breakers like MCCB and ACB.
Ideally, one MCU with an ADP2450 with some passive components can build up a complete ETU system. Therefore, ADP2450 can be called a companion part for the MCU for low voltage circuit breaker applications.
The key features of ADP2450 are listed as below:
FB1
COUT1
VOUT1
RTOP1
RBOT1PGND1
VOUT2L2
COUT2
FB2
SW2VIN
CIN2
VOUT1
PGND2
nRSTO
Rect Bridge
VCORE
MCU
RST
D1CT1
VPTH
RTOP_VP
Rect BridgeCT2
Rect BridgeCT3
Rect BridgeCT4
EIN1
EIN2
EIN3
EIN4
EOUT1
EOUT2
EOUT3
EOUT4
ADC1
ADC2
ADC3
ADC4
RCS1
RCS2
RCS3
RCS4
RPOWER
GPIO
DRV1
DET
AVDDVOUT2
GAIN0GAIN1
GPIO
ADC5
Actuator
BST2CBST
RGAIN
R2
REF
RBOT_VP
VCOM
RCOM
VoltageMonitoring
Boost ShuntControl
Buck Regulator
PGA 1
PGA 2
PGA 3
PGA 4
Gain Selection
Power Detection
DC Offset andCompenstion
GND
VREG
CREG
RTRPVOUT1
GATE TRG
VTRP
EOUT5
ZCT
RZCT EIN5_PEIN5_N
Actuator
R1
R3
R4
VREF
R5
VREF
Common Control Block
Actuator Driver
Analog Trip
EA5
Ampli�er 5
X It offers a low power shunt boost controller to convert a current source (output from current transformer) into a voltage source. Additionally, it has a power detection circuit which can flexibly set a system level startup current and hysteresis.
X It offers a 36 V high voltage input buck regulator, which can effectively regulate out a 3.3 V/5 V/Adj power supply for the MCU and signal condition circuit. The output current is up to 500 mA.
X One integrated power supply supervisor circuit offers a safe system level reset.
X 4× programmable PGAs with 15 different gain setting options have been integrated into the ADP2450. The PGAs can also support two different topologies (invert and differential mode) to interface different CT topologies (single coil or dual coil).
X An interior op amp can be used as a signal amplifier for ground faults, leakage, residual current detection, and more.
X 4× threshold value programmable analog trip units inside can be used to implement the MCR (making current release) functions for the ACB. The analog trip can support both single coil and dual coil user cases based on different package models.
X One integrated actuator driver.
X Enhanced temperature range covers –40°C to +125°C.
X ±8 V OVP and 4 kV ESD protection (HBM) for the PGA input to offer a higher level of system protection.
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System Block DiagramsMCCB System Solution
ACB System Solution
Aux Power Supply(for example, 24 VDC)
SampleResistor
3.3 VIa
Ib
Ic
In
ADP2450
ADR3430
MCU
ADM2587E
Aux Power Supply(for example, 24 VDC)
3.3 V
···
ADP2450
AD7779
MCU
ADM2587E
Other Relevant Product IntroductionPart Number Description Key Features Benefits
Interface
ADM2587E Isolated RS485 interface IC
X Isolated RS-485/RS-422 transceiver, configurable as half or full duplex
X isoPower® integrated isolated dc-to-dc converter X ±15 kV ESD protection
One IC integrates isolated power supply, signal isolation, and RS-485 interface driver, and reduces PCB space
Voltage Reference
ADR3430Low power and low cost voltage reference
X Initial accuracy: ±0.1% (maximum) X Maximum temperature coefficient: 8 ppm/°C X Operating temperature range: −40°C to +125°C X Quiescent current: 100 μA (maximum) X Low dropout voltage: 250 mV at 2 mA X Output noise (0.1 Hz to 10 Hz): <10 μV p-p at 1.2 V (typical) X 6-lead SOT-23
Low power, low dropout voltage, and low cost
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Design ResourceADP2450 EVB Board
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Free Samplesanalog.com/sample
Technical Hotline1-800-419-0108 (India)
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3rd Party Reference DesignTianJin Free Soar Innovations Technology Co., Ltd.— freesoar.net
X Measurement functions: currents, voltages, frequency, energy, frequency factor, etc.
X Protection functions
X MCCB ETU and support RCD function
X LCD display
X Support RS-485 and Modbus-RTU protocol
Documents—AN/Articles X ADP2450ACPZ-1-EVALZ User Guide X AN-0971 Recommendations for Control of Radiated Emissions with
isoPower Devices
