Cirrus-logic AN337 Manuel d'utilisateur télécharger pdf

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CS5463: Determining No-load Condition Without

Violating Starting Condition Standards

1. INTRODUCTION

When the CS5463 is used in power meter applications, some customers use the I

RMS

residual value as the

threshold for the external microprocessor to decide if the meter is under the no-load condition, and then find

the meter can not pass the starting test. This applications note gives the reason and the correct solution.

2. NO-LOAD AND STARTING CONDITIONS

According to the standard IEC 62053-22, the definition of a no-load condition is defined as: "When the volt-

age is applied with no current flowing in the current circuit, the test output of the meter shall not produce

more than one pulse.". The test of starting condition is defined as: "The meter shall start and continue to

To meet these requirements, a power meter has to use the correct no-load threshold in order to restrain the

pulse output and energy accumulation when there is no load current but resume pulse output and energy

accumulation when the load is above the starting current (I

3. DETERMINING A NO-LOAD CONDITION CORRECTLY

The CS5463 has three energy pulse outputs (E1, E2, and E3). The pulse outputs under no-load or starting

condition has been well manipulated by the CS5463. In addition, the CS5463 has a no-load threshold reg-

ister (LOAD

Min

) to help disable the active energy pulse output under some specified condition. When the

magnitude of the P

Active

Min

, the active energy pulse output is disabled.

Different from the energy pulses, the energy register, either mechanical or electronic, is normally manipu-

lated by a microcontroller. The microcontroller needs to use a variable and a threshold value to decide if the

meter is under a no-load condition, in which case the values in the power registers should be discarded.

There are two options to select the variable and the threshold.

Table 1: Variable & Threshold Values Comparison

Because I

RMS

exhibits much more system noise than P

Active

, I

RMS

should not be used as a variable

to determine the no-load condition.

Variable

Used

Threshold Value

Compare

Result

RMS

Residual value (AC offset) with

inputs of U

and no current

BAD

Active

Less than the value with inputs of U

and starting current

GOOD

AN337

DEC '08

AN337REV1

1 2

1. INTRODUCTION 1
2 AN337REV1 2

Résumé du contenu

Page 1 - 1. INTRODUCTION

Page 2 - 2 AN337REV1

2 AN337REV1AN337For example, assume a 10(60)A Class 0.5 watt-hour meter using a 200 uΩ shunt as the current sensor. Thevoltage on the CS5463 I-channel

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Cirrus-logic AN337 Manuel d'utilisateur

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