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Programmable Three Phase Power / Energy Metering IC for Stepper Motor / Impulse Counter Applications SA2005P
FEATURES + Direct drive for + + + +
electro-mechanical counters or stepper
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+ + + + + +
Meets the IEC 521/1036 Specification requirements for Class 1 AC Watt hour meters Operates over a wide temperature range Easily adaptable to different signal levels Adaptable to different types of sensors Precision voltage reference on-chip Protected against ESD
motors Calibration and setup stored on external EEPROM - no trim-pots required Flexible programmable features providing ease of implementation for meter manufacturers Per phase energy direction and voltage fail indication Precision oscillator on chip
DESCRIPTION
The SAMES SA2005P provides a single chip active energy metering solution for three phase mechanical counter-based meter designs. Th SA2005P does not require any external trim-pots or resistor ladders for meter calibration. Calibration and meter configuration information is stored on a small external EEPROM. Meter setup stored on the EEPROM includes various metering direction modes (total sum, absolute sum, positive or negative energy) phase calibration data, rated metering conditions, LED pulse rate, counter pulse width, counter resolution and creep current. A programmable rate pulse output is available for meter calibration purposes. Per phase voltage fail and voltage sequence faults as well as energy direction indication are available as LED outputs. Programmable dividers enable various mechanical counter or stepper motor counter resolutions. A precision oscillator, that replaces an external crystal, is integrated on chip. A voltage reference is integrated on chip. The SA2005P integrated circuit is available in 24-pin dual in line plastic (DIP-24) and small outline (SOIC-24) package options.
VDD VSS
IIN1 IIP1 IVN1 IIN2 IIP2 IVN2 IIN3 IIP3 IVN3 GND
I1 X V1 I2 X V2 I3 X V3
CHANNEL BALANCE PROGRAMPROG. CHANNEL ADDER BALANCE CHANNEL BALANCE MABLE ADDER POWER TO PULSE RATE
LED MON MOP PH / DIR PH1 PH2 PH3
REF
TIMING & CONTROL
OSC
INTERFACE
RLOAD
dr-01605
VREF
TEST
SCL
SDA
Figure 1: Block diagram
SPEC-0086 (REV. 2)
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SA2005P ELECTRICAL CHARACTERISTICS
(VDD = 2.5V, VSS = -2.5V, over the temperature range -10C to +70C#, unless otherwise specified.) Parameter Operating temp. Range Supply Voltage: Positive Supply Voltage: Negative Supply Current: Positive Supply Current: Negative Current Sensor Inputs (Differential) Input Current Range Voltage Sensor Input (Asymmetrical) Input Current Range Pin VREF Ref. Current Ref. Voltage Digital I/O Pins RLOAD, TEST, SDA Input High Voltage Input Low Voltage Pins MOP, MON, LED, SCL, PH/DIR, PH1, PH2, PH3 Output High Voltage Output Low Voltage Pin SDA Pull up current Pins TEST, RLOAD Pull down current VIH VIL VDD-1 VSS+1 V V IIV -IR VR -25 45 1.1 50 +25 55 1.3 A A V III -25 +25 A Symbol TO VDD VSS IDD ISS Min -25 2.25 -2.75 15 15 Typ Max +85 2.75 -2.25 16 16 Unit C V V mA mA
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Condition
Peak value
Peak value With R = 24kW connected to VSS Reference to VSS
VOH VOL -IIL IIH
VDD-1 VSS+1 24 48 54 110
V V A A
IOH = -2mA IOL = 5mA VI = VSS VI = VDD
#Extended Operating Temperature Range available on request.
ABSOLUTE MAXIMUM RATINGS*
Parameter Supply Voltage Current on any pin Storage Temperature Operating Temperature Symbol VDD -VSS IPIN TSTG TO Min -0.3 -150 -40 -40 Max 6.0 +150 +125 +85 Unit V mA C C
*Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only. Functional operation of the device at these or any other condition above those indicated in the operational sections of this specification, is not implied. Exposure to Absolute Maximum Ratings for extended periods may affect device reliability.
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SA2005P PIN DESCRIPTION
PIN 20 6 18 21, 24, 3 23, 22, 2, 1, 5, 4 19 Designation GND VDD VSS IVN1, IVN2, IVN3 IIN1, IIP1, IIN2, IIP2, IIN3, IIP3 VREF Description Analog Ground. The voltage to this pin should be mid-way between VDD and VSS.
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Positive supply voltage. Typically +5V if a current transformer is used for current sensing. Negative supply voltage. Typically 0V if a current transformer is used for current sensing. Voltage sense inputs. The current into the A/D converter should be set at 14ARMS at nominal mains voltage. The voltage sense input saturates at an input current of 25A peak. Inputs for current sensors. The termination resistor voltage from each current transformer is converted to a current of 16ARMS at rated conditions. The current sense input saturates at an input current of 25A peak. This pin provides the connection for the reference current setting resistor. A 24kW resistor connected to VSS sets the optimum operating condition. Serial clock output. This output is used to strobe data from the external EEPROM. Serial data. Send and receive data from an external EEPROM. Test input. For normal operation connect this pin to VSS. Calibration LED output. Refer to section Led Output (LED) for the pulse rate output options. Motor pulse outputs. These outputs can be used to drive an impulse counter or stepper motor directly. Multiplexed phase or direction driver output. Triggers a data reload from the external EEPROM. Multiplexed LED drivers for direction and mains fail indication.
8 9 17 10 11, 12 13 7 14, 15, 16
SCL SDA TEST LED MON, MOP PH / DIR RLOAD PH1, PH2, PH3
ORDERING INFORMATION
IIP2 IIN2 IVN3 IIP3 IIN3
VDD
1 2 3 4 5 6 7 8 9 10 11 12 dr-01602
24 23 22 21 20 19
IVN2
Part Number
IIN1 IIP1 IVN1 GND VREF
Package DIP-24 SOIC-24
SA2005PPA SA2005PSA
RLOAD SCL SDA LED MON MOP
18 VSS 17 16 TEST PH3
15 PH2 14 PH1 13 PH / DIR
Figure 2: Pin connections: Package: DIP-24, SOIC-24
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SA2005P FUNCTIONAL DESCRIPTION
The SAMES SA2005P is a CMOS mixed signal analog/digital integrated circuit that performs three phase power/energy calculations across a power range of 1000:1 to an overall accuracy of better than Class 1. The integrated circuit includes all the required functions for 3phase power and energy measurement such as oversampling A/D converters for the voltage and current sense inputs, power calculation and energy integration. Internal offsets are eliminated through the use of cancellation procedures. The integrated circuit includes all the required functions for a three phase mechanical counter-based meter design. A precision oscillator, that replaces an external crystal, is integrated on chip providing a temperature stable time base for the digital circuitry. A temperature stable voltage reference integrated on chip generates the reference current used by the analog circuitry. Voltage and currents are sampled simultaneously by means of a sigma delta modulator type ADC and power is calculated for each individual phase. A programmable channel balance on each channel is used for individual channel calibration. The scaled power is fed to a programmable adder that allows the representation of the measured energy to be either total sum or absolute sum. The summed power is integrated and divided down to represent integrated energy. Pulses on the LED output and on the mechanical counter outputs represent measured amounts of energy. The programmable dividers provide flexible counter and calibration LED resolutions. Outputs for phase voltage fail and voltage sequence faults and energy direction are available. The SA2005P does not require any external trim-pots or resistor ladders as meter calibration and configuration data is stored on a small external EEPROM. The SA2005P configures itself from the EEPROM during power up. These features enables meter manufacturers flexible meter designs from a single integrated circuit.
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operation of the meter. Every data byte stored in the EEPROM is protected with a checksum byte to ensure data integrity.
ELECTROSTATIC DISCHARGE (ESD) PROTECTION
The SA2005P integrated circuit's inputs/outputs are protected against ESD.
POWER CONSUMPTION
The overall power consumption rating of the SA2005P integrated circuit is less than 80mW with a 5V supply.
INPUT SIGNALS
ANALOG INPUT CONFIGURATION
The current and voltage sensor inputs are illustrated in figure 3. These inputs are protected against electrostatic discharge through clamping diodes, in conjunction with the amplifiers input configuration. The feedback loops from the outputs of the amplifiers AI and AV generate virtual shorts on the signal inputs. Exact duplications of the input currents are generated for the analog processing circuitry. The current and voltage sense inputs are identical. Both inputs are differential current driven up to 25A peak. One of the voltage sense amplifiers input terminals is internally connected to GND. This configuration is possible because the voltage sense input is much less sensitive to externally induced parasitic signals compared to the current sense inputs.
Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)
The current sense inputs connects to a termination resistor connected across the terminals of a current transformer. At
V DD
IIP
CURRENT SENSOR INPUTS
VSS VDD
AI
IIN
VSS VDD
IVP
AUTOMATIC DEVICE CONFIGURATION (BOOT UP)
During power up, registers containing configuration and calibration information is updated from an external EEPROM. The device itself never writes tot he EEPROM so any write protect features offered by manufacturer of EEPROM's may be used to protect the configuration and calibration constant of the meter. The device reloads its configuration every 1193 seconds from the external EEPROM in order to ensure correct
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VOLTAGE SENSOR INPUT
V SS
AV
GND DR-01288
Figure 3: Analog input internal configuration
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rated current the resistor values should be selected for input currents of 16ARMS. Referring to figure 8, the resistors R1 and R2 on current channel 1, resistors R3 and R4 on current channel 2 and resistors R5 and R6 on current channel 3, define the current level into the current sense inputs of the SA2005P. The current sense inputs saturates at an input current of 25A peak. Resistors R29, R30 and R31 are used as current transformer termination resistors. The voltage drop across the termination resistors should be at least 20mV at rated conditions. Values for the current sense inputs are calculated as follows: R1 = R2 = ( IL / 16ARMS ) x R29 / 2 R3 = R4 = ( IL / 16ARMS ) x R30 / 2 R5 = R6 = ( IL / 16ARMS ) x R31 / 2 Where: IL = Line current/CT-ratio In case a current transformer is used for current sensing the value of the termination resistors should be less than the resistance of the CT's secondary winding.
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Reload (RLOAD)
A falling edge on the RLOAD pin will trigger a register update from the external EEPROM. This feature may be used during calibration to load updated register data in the SA2005P. For normal operation of the SA2005P the RLOAD pin may be left floating.
Test Inputs (TEST)
The TEST input is the manufacturers test pin and must be connected to VSS in a metering application.
OUTPUT SIGNALS
LED Output (LED)
Four options for the LED output pulse rate are available, 6400, 3200, 1600 pulses per kWh, and a pulse rate of 1252 pulses per second at rated conditions. At 1252 pulses per second t LED is 71s, for the other options tLED is 10ms. The LED output is active low as shown in figure 4.
VDD
LED
VSS
DR-01332
Voltage Sense Inputs (IVN1, IVN2, IVN3)
The mains voltage are measured by means of a resistor divider and the divided voltage are converted to a current. The current into the voltage sense inputs (virtual ground) should be set to 14ARMS at rated voltage conditions. The individual mains voltages are divided down to 14VRMS per phase. The resistors R12, R13 and R14 (figure 8) set the current for the voltage sense inputs. The voltage sense inputs saturate at an input current of 25uA peak.
tLED
Figure 4: LED pulse output
Motor Output (MOP, MON)
The motor pulse width is programmable for 71ms, 142ms and 284ms. The MON pulse will follow the MOP pulse within the selected pulse width time. This prevents the motor armature being in the wrong position after a power failure. Both MOP and MON outputs are active high. A MOP pulse followed by a MON pulse represents one energy pulse. The motor drive waveforms are shown in figure 5.
VDD MOP VSS
Voltage Reference Connection (VREF)
A bias resistor of 24k provides an optimum bias conditions on chip. Calibration of the SA2005P is done by means of divider ratios stored on an external EEPROM. This is described in the Device Configuration section.
Serial Data (SDA)
The SDA pin connects directly to the SDA pin of an external EEPROM. The pin is used to transfer data between the EEPROM and the SA2005P. An external pull-up resistor in not needed.
VDD MON VSS
DR-01559
tm
tm
tm
Figure 5: Motor drive on MON and MOP pins of device
Serial Clock (SCL)
The SCL pin connects directly to the SCL of an external EEPROM. The SCL output is used to strobe data at a rate of 50kHz out of the EEPROM. An external pull up resistor is not needed. The SCL output uses a soft driver and may be overdriven by the calibration equipment.
Multiplex Output (PH/ DIR)
The PH/DIR output enables either direction or voltage information on the phase LED driver outputs (PH1, PH2 and PH3). This multiplex output switches between logic 1 and 0 at a frequency of approximately 280Hz. A logic 1 enables energy direction information on the LED driver outputs and a logic 0 enables voltage information.
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SA2005P
The PH/Dir output is used in conjunction with the LED driver outputs to display information about each individual phase, see figure 6.
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inputs are out of phase (greater than 90 degrees). Positive energy flow is defined as the condition where the voltage sense and current sense inputs are in phase. PH/DIR = 0 (Voltage fail / phase sequence error) When PH/DIR is low (logic 0) voltage information is available on PH1, PH2 and PH3. A logic 0 on any of these pins indicates a voltage failure, the SA2005P does not detect a zero crossing on the applicable voltage sense input. Referring to figure 6 the voltage fail LED will be on when the voltage phase is present and off when the voltage phase is missing. In the case of a phase sequence error all three LED driver outputs PH1, PH2 and PH3 will pulse with a repetition rate of approximately 1Hz.
Phase LED Drivers (PH1, PH2, PH3)
The LED driver outputs present either direction information or voltage information. The three LED driver outputs are used in conjunction with the PH/DIR output to display information about each individual phase (refer to figure 6) as follows: PH/DIR = 1 (Direction indication) When PH/DIR is high (logic 1) energy direction information for each individual phase is available on PH1, PH2 and PH3. A logic 0 indicates reverse energy flow and a logic 1 indicates positive energy flow. Reverse energy flow is defined as the condition where the voltage sense input and the current sense
PH (Sink) DIR (Drive) VFAIL 1 Channel 1 DIR 1 VFAIL 2 Channel 2 DIR 2 VFAIL 3 Channel 3 DIR 3
dr-01603
PH/DIR
D1 R9 DIR1
D2 VFAIL1
D3 DIR2
D4 VFAIL2
D5 DIR3
D6 VFAIL3
PH1 R10 PH2
R11 PH3
Figure 6: Multiplexing of the LED Drivers
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SA2005P ANTI-TAMPER CONDITIONS
The SA2005P cater for the following meter tamper conditions and are indicated as follows: Method Phase Voltages Description One LED is provided for each phase to indicate abnormal operating conditions.
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Result During normal conditions, the LEDs are continuously switched on. The SA2005P will record the energy consumption accurately under this condition The SA2005P will record the energy consumption accurately under this condition The SA2005P will record the energy consumption accurately under this condition
Phase Failure, In case of a phase failure, the corresponding LED is no voltage switched off. Phase In case of phase sequence error, all LEDs are flashing with a reSequence petition rate of approximately 1 Hz. A connection of a line voltage Error to the neutral terminal would be indicated in the same way. Input / Output One LED is provided for each current sensor to indicate reverse energy flow. If detected, the corresponding LED is switched on. Terminals Interchanged The SA2005P can be configured to accumulate the absolute energy consumption for each phase measured, irrespective of the direction of the energy flow. Missing The architecture of the meter should provide for a good "phantom Neutral neutral" in cases where the neutral is disconnected from the Connection meter. Return The SA2005P will therefore record the energy consumption through Earth accurately under this condition. Load Imbalance The calibration data is stored in an EEPROM. There are no Calibration trim-pots required in this design.
In this case, the meter would register the energy consumption correct. A indication for this condition could be realized external to the IC. The SA2005P will record the energy consumption accurately under this condition The meter can not be re-adjusted, only reprogrammed.
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SA2005P DEVICE CONFIGURATION
SIGNAL FLOW DESCRIPTION
The following is an overview of the SA2005P's registers. For a detailed description of each parameter please refer to parameter description section. Figure 7 shows the various registers in the SA2005P's power to pulse rate block. The inputs to this block are three single bit pulse density modulated signals, each having a pulse rate of 641454 pulses per second at rated conditions. The parameters Cb1, Cb2, Cb3, Sum, Ct, Kr, CresH, CresL, Cled and Pw contain values that are read from the external EEPROM during power up. The Pre-Divider registers are used for calibration and to balance the gain of each channel. The Programmable Adder is used to select between the total sum or absolute sum of the measured energy. The Creep current threshold detector selects the creep current which is relative to the meters rated current. The Rated Condition register is used to program the rated condition of the meter and feeds the registers LEDconstant and Counter Resolution with the applicable pulse rate. These two registers are programmed to select the LED output rate and the counter resolution (pulses per kWh) respectively. The Counter Pulse Width register is used to program the pulse width for the mechanical counter driver output MOP and MON. EEPROM Memory Allocation The following table shows the EEPROM memory allocation as well as the corresponding name. The uneven byte always Description Channel Balance 3 Channel Balance 1 Channel Balance 2 Summing mode Creep current threshold Rated Condition Led Pulse-rate Counter Resolution (LSB) Counter Resolution (MSB) Counter Pulse-Width E2Address 10 11 12 13 14 15 16 16 17 20 21 22 23 24 25 26 26 27
Power from S - D converters 641454 pulses/s Power from S - D converters 641454 pulses/s
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Power from S - D converters 641454 pulses/s
Pre-Divider /Cb1
Pre-Divider /Cb2
Pre-Divider /Cb3
Programmable Adder SUM
Creep current threshold detector Ct
Rated Condition /Kr
Normally 1253p/s
Normally 6400p/kWh
Counter Resolution CresH, CresL
LED-Constant Cled
Counter Pulse width Pw
MOP
MON
LED
Figure 7: Signal flow block diagram contains a XORed byte of the previous even byte. This is the checksum byte used by the SA2005P to ensure data integrity. Contents Cb3 XOR of ADDR 10 Cb1 XOR of ADDR 12 Cb2 XOR of ADDR 14 SUM Ct XOR of ADDR 16 Kr XOR of ADDR 20 Cled XOR of ADDR 22 CresL XOR of ADDR 24 ClresH Pw XOR of ADDR 26 Bit [7:0] ---v vvvv xxxx xxxx ---v vvvv xxxx xxxx ---v vvvv xxxx xxxx ---- --vv v--- ---xxxx xxxx vvvv vvvv xxxx xxxx ---- --vv xxxx xxxx vvvv vvvv xxxx xxxx ---v vvvv vv-- ---xxxx xxxx D26 D26 D24 D22 D20 D16 D16 D13 D12 Name D10
KEY: (- = DON'T CARE); (V = VALUE/PARAMETER); (0,1 = LOGICAL VALUE); (X = BIT-XOR)
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SA2005P
PARAMETER DESCRIPTION
Refer to the EEPROM memory allocation map as well as the Signal flow diagram figure 7, for a description of the registers used in this section. Rated Condition (Kr) Kr is used to program the rated condition of the meter. Rated conditions from less than 10A to several 100A are possible. The rated conditions divider as well as the pre-divider is used to compensate for individual phase calibration. The three phases are calibrated to the phase with the lowest gain. Kr is calculated as follows: Krx=642 000/Rated volt/Rated current/6400x3600x1000/512 The SA2005P's internal counters count from 0 so 1 must be subtracted from Kr: Kr = round(Krx)-1 Where: Krx is the real value Kr is the integer value Kr is made up of 1 byte (D20) Pre-divider (Cb1, Cb2, Cb3) The channel balance (Cb) value is used to balance the three phases. The rated conditions divider ratio must be calculated. Error measurements per phase are done with channel balance values set to zero. The measured error values are used to correct the error measurements of the three phases. The rounding error in the rated conditions divider is also compensated for in the channel balance calculations. One count on the channel balance value represent 100%/256. Gain = ((Krx-Kr+1) / Krx) x 100 Gain calculates the rounding error made by the rated conditions divider. Cb1 = (CHB1 - CBMIN + Gain) x 256 / 100 Cb2 = (CHB2 - CBMIN + Gain) x 256 / 100 Cb3 = (CHB3 - CBMIN + Gain) x 256 / 100 CHB1, CHB2, CHB3 is the measured channel balance %error that will be corrected CBMIN is the lowest channel balance %error measured between the three phases.
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LED Pulse-Rate (Cled) Two bits of byte D22 allow for the selection of 4 different LEDPulse-rates. The LED pulse-width is 10ms. In fast pulse mode, the pulse-width is set to 71s. D22[1] 0 1 1 0 D22[0] 1 0 1 0 Calibration LED - Output 6400 p/kWh 3200 p/kWh 1600 p/kWh 1252 pulses/second @ rated for fast calibration Counter Resolution (Cres) A 13 bit divider divide the pulse rate from the rated conditions divider down to the desired counter resolution. Cres is made up of bits 0 of 4 of byte D26 and byte D27. D26[4:0] D27[7:0] Counter Resolution
Counter Pulse-Width (Pw) The pulse width for the mechanical counter driver output is selectable to accommodate various step-motor and impulsecounter requirements. Pw is made up of bits 7 and 6 of byte D26. D26[7] 1 0 0 D26[6] 1 0 Counter Pulse-Width 284 ms 142 ms 71 ms
Creep current threshold (Ct) The creep current is expressed relative to the rated current of the meter. The SA2005P will not meter currents below the creep current. The creep current is implemented to prevent the meter from accumulating energy when no load is connected. Cs is made up of bit 7 of byte D16 D16[7] 0 1 Creep threshold 0.02% of rated current 0.01% of rated current
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SA2005P
Programmable adder mode (SUM) The SA2005P can be programmed to sum the energy measurement as follows: Total sum This represents the total sum of the energy measured on all three phases flowing through the current sensors. Negative energy flow is taken into consideration. Energy = Energy phase 1 + Energy Phase 2 + Energy Phase 3 Absolute sum This represents the sum of the energy measured on all three phases, regardless of the direction of energy flow through the current sensors. Power = abs (Energy phase 1) + abs (Energy phase 2) + abs (Energy phase 3) During calibration the device may be programmed to use only a specific phase for energy measurement. This can be used for channel balancing. D16[2] D16[1] D16[0] Counter Resolution 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 Total sum all three phases Only phase 1 measurement Only phase 2 measurement Only phase 3 measurement Absolute sum of all three phases Only phase 1 measurement Only phase 2 measurement Only phase 3 measurement
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Calculate the Channel balance values: During the rated conditions calculation the rated condition register was rounded and any rounding errors is now taken into account: Gain = ((Krx - Kr+1 ) / Krx) x 100 Gain = ((38.3327 - 38) / 38.337) x 100 Gain = 0.8679 The real channel balance errors still need to be measured so CHB1,CHB2, CHB3 and CBMIN are set to 0 for all phases. Calculate the Pre-divider values: Cb1 = (CHB1 - CBMIN + Gain ) x 256 / 100 Cb1 = (0% - 0% + Gain ) x 256 / 100 Cb1 = Gain x 256 / 100 Cb1 = 0.8679 x 256 / 100 Cb1 =2.2218 Convert to integer Cb1 = 2 At this stage all three channels will be set with the same values, Cb1= Cb2= Cb3. Store the calculated values in the EEPROM. Ensure that the SA2005P reload's its registers from the EEPROM by means of the reload pin (RLOAD) or power down the meter and power up again. The meter is now set up with the correct register values but not yet calibrated. The following example shows how to calibrate the meter Use the rated conditions divider value and the channel balance values calculated above and program the EEPROM. Set the programmable adder for a single phase to be measured. Measure the %error for each individual phase without changing any of the calibration constants. %Error=(Measured Energy-Real Energy)/Real Energyx100 The %Error will be worked back into the calculations above. For the example we will assume a 1.5%, 5.2%, and 3.2% for the three individual phases. The rated conditions value is recalculated relative to the phase with the lowest error. Phase 1 has the lowest error so 1.5% = MinError;
Example of calculating rated conditions and channel balance values Meter rating = 80A / 230V (The SA2005P only uses integer values) Calculate the rated conditions: Krx=642 000/Rated volt/Rated current/6400x3600x1000/512 Krx = 642 000/230/80/6400x3600x1000/512 Krx = 38.3327 Krx = 38 (round Krx) - convert to integer Kr = 38 - 1 = 37 The value 37 is stored in the rated register (Kr).
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SA2005P
Recalculate the rated conditions Krx = 642 000 / Rated volt / Rated current / 6400 x 3600 x 1000 / 512 x (1 + %MinError / 100 ) Krx = 642 000 / 230 / 80 / 6400 x 3600 x 1000 / 512 x 1.015 Krx = 38.9077
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Kr = 38 - 1 = 37
The 37 are stored in the rated register. The channel balance values are adjusted to make provision for the rounding error. Gain = ((Krx - Kr +1 ) / Krx ) x 100 Gain = (( 38.9077 - 38 ) / 38.9077 ) x 100 Gain = 2.33 The channel balance pre-devider value must be recalculated. (BMIN will be the lowest %error value, in this case 1.5%, CHB1, CHB2 and CHB3 are the individual phase %errors measured. Cb1 = (CHB1 - CBMIN + Gain ) x 256 / 100 Cb1 = (1.5 - 1.5 + 2.33 ) x 256 / 100 = 5.97 =5 Cb2 = (CHB2 - CBMIN + Gain ) x 256 / 100 Cb2 = ( 5.2 - 1.5 + 2.33 ) x 256 / 100 = 15.43 = 15 Cb3 = (CHB3 - CBMIN + Gain ) x 256 / 100 Cb3 = (3.2 - 1.5 + 2.33 ) x 256 / 100 = 10.316 = 10 Store the calculated values in the EEPROM and the meter is calibrated.
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SA2005P TYPICAL APPLICATION
CALCULATION OF EXTERNAL RESISTOR VALUES
In figure 8, all the components required for a three-phase power/energy metering section, is shown. The application uses current transformers for current sensing. The 4-wire meter section is capable of measuring 3x230V/80A with precision better than Class 1 The most important external components for the SA2005P integrated circuit are the current sense resistors, the voltage sense resistors as well as the bias setting resistor. Bias Resistor R7 defines all on-chip and reference currents. With R7=24kW, optimum conditions are set. CT Termination Resistor The voltage drop across the CT termination resistor at rated current should be at least 20mV. The CT's used have low phase shift and a ratio of 1:2500.The CT is terminated with a 2.7W resistor giving a voltage drop across the termination resistor 864mV at rated conditions (Imax for the meter). Current Sense Resistors The resistors R1 and R2 define the current level into the current sense inputs of phase one of the device. The resistor values are selected for an input current of 16A on the current inputs at rated conditions. According to equation described in the Current Sense inputs section: R1 = R2 = ( IL / 16A ) x RSH / 2 = 80A /2500 / 16A x 2.7W / 2 = 2.7kW IL = Line current / CT Ratio The three current channels are identical so R1 = R2 = R3 = R4 = R5 = R6.
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Voltage Divider The three voltage divider for voltage measurement are identical so resistor values for one phase will be calculated. The voltage divider is calculated for a voltage drop of 14V. Equations for the voltage divider in figure 5 are: RA = R16 + R19 + R22 RB = R8 || R13 Combining the two equations gives: (RA + RB ) / 230V = RB / 14V Resistor values R11 = R12 = R13= 24kW and R8 =1MW is chosen. Substituting the values result in: RB = 23.4375kW RA = RB x (230V / 14V - 1) RA = 361.607kW. Resistor values of R16, R19 and R22 is chosen to be 130k, 130k and 100k. The three voltage channels are identical so R14= R15= R16 , R17 = R18 = R19 and R20 = R21= R22.
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SA2005P
Neutral GND R18 V3 In R16 R19 R22 R25 R15 R20 R23 R26 R21 R24
V2 In
V1In
CT1 R29
R1
U1 23 IIN1 GND IVN1 20 GND 21 24 R12 R13
R17 C5
R2 GND CT2 R30 R3
Figure 8: Typical application circuit
V3 Out V2 Out V1 Out 1 2 3 4 VSS
22
IIP1 IVN2
C4
2
IIN2
IVN3 PH/DIR
3 13
R14
C3
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R4 GND CT3 R31 R6 GND R7 R5
1
IIP2 PH1 IIN3 PH2 PH3 14 15 16 12 R9 R10 R11
D1 DIR1
D2 VFAIL1
D3 DIR2
D4 VFAIL2
D5 DIR3
D6 VFAIL3
5
4
IIP3 MOP
CNT1
19 18 17
6 5 4 3 2 1 .1
VREF MON VSS LED TEST VDD SCL SDA dr-01604 SDA SCL RLOAD 7 RELOAD 6 GND R28 C1 11 D7 10 R8 Counter VDD R27 C2
VDD
VDD U2 A0 A1 A2 VSS 24C01A VCC TEST SCL SDA 8 7 6 5 VSS
8 9
C6
VSS
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SA2005P
Parts List for Application Circuit: Figure 7
Symbol U1 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 R31 C1 C2 C3 C4 C5 C6 D1 D2 D3 D4 D5 D6 U2 CNT1 CT1 CT2 CT3 Description SA2005P Resistor, 2.7k, 1/4W, 1%, metal Resistor, 2.7k, 1/4W, 1%, metal Resistor, 2.7k, 1/4W, 1%, metal Resistor, 2.7k, 1/4W, 1%, metal Resistor, 2.7k, 1/4W, 1%, metal Resistor, 2.7k, 1/4W, 1%, metal Resistor, 24k, 1/4W, 1%, metal Resistor, 1k, 1/4W, 5%, carbon Resistor, 1k, 1/4W, 5%, carbon Resistor, 1k, 1/4W, 5%, carbon Resistor, 1k, 1/4W, 5%, carbon Resistor, 1M, 1/4W, 1%, metal Resistor, 1M, 1/4W, 1%, metal Resistor, 1M, 1/4W, 1%, metal Resistor, 24k, 1/4W, 1%, metal Resistor, 24k, 1/4W, 1%, metal Resistor, 24k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 130k, 1/4W, 1%, metal Resistor, 100k, 1/4W, 1%, metal Resistor, 100k, 1/4W, 1%, metal Resistor, 100k, 1/4W, 1%, metal Resistor, 1k, 1/4W, 1%, metal Resistor, 1k, 1/4W, 1%, metal Resistor, 2.7W, 1/4W, 1%, metal Resistor, 2.7W, 1/4W, 1%, metal Resistor, 2.7W, 1/4W, 1%, metal Capacitor, 220nF Capacitor, 220nF Capacitor, 1.5F, 16V, electrolytic Capacitor, 1.5F, 16V, electrolytic Capacitor, 1.5F, 16V, electrolytic Capacitor, 820nF 3mm Light emitting diode 3mm Light emitting diode 3mm Light emitting diode 3mm Light emitting diode 3mm Light emitting diode 3mm Light emitting diode 24C01A, 1kbit EEPROM Mechanical stepper motor counter Current Transformer, TZ76 Current Transformer, TZ76 Current Transformer, TZ76 Detail DIP-24 / SOIC-24 Note 1 Note 1 Note 1 Note 1 Note 1 Note 1
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Note 1 Note 1 Note 1
Note 2 Note 2 Note 2 Note 3 Direction indicator V1 Fail indicator Direction indicator V2 Fail indicator Direction indicator V3 Fail indicator
2500:1 2500:1 2500:1
Note 1: Resistor (R1 to R6) values are dependent on the selection of the termination resistors (R29 to R31) and CT combination Note 2: Capacitor values may be selected to compensate for phase errors caused by the current transformers. Note 3: Capacitor C6 to be positioned as close as possible to supply pins VDD and VSS of U1 as possible.
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SA2005P PM9607AP
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SA2005P PM9607AP DISCLAIMER:
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The information contained in this document is confidential and proprietary to South African Micro-Electronic Systems (Pty) Ltd ("SAMES") and may not be copied or disclosed to a third party, in whole or in part, without the express written consent of SAMES. The information contained herein is current as of the date of publication; however, delivery of this document shall not under any circumstances create any implication that the information contained herein is correct as of any time subsequent to such date. SAMES does not undertake to inform any recipient of this document of any changes in the information contained herein, and SAMES expressly reserves the right to make changes in such information, without notification, even if such changes would render information contained herein inaccurate or incomplete. SAMES makes no representation or warranty that any circuit designed by reference to the information contained herein, will function without errors and as intended by the designer.
Any sales or technical questions may be posted to our e-mail address below: energy@sames.co.za
For the latest updates on datasheets, please visit our web site: http://www.sames.co.za. SOUTH AFRICAN MICRO-ELECTRONIC SYSTEMS DIVISION OF LABAT TECHNOLOGIES (PTY) LTD Tel: (012) 333-6021 Tel: Int +27 12 333-6021 Fax: (012) 333-8071 Fax: Int +27 12 333-8071
P O BOX 15888 33 ELAND STREET LYNN EAST 0039 REPUBLIC OF SOUTH AFRICA
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