WG3-6-7-10-03-007Teleconference 10/03/15

Cover page forcontributions to the PC62.36 revision

PC62.36Clause Number and Title / 7.1 Rated Voltage Test and 7.2 Rated Current Test
Comment Submitted By / Al Martin, Tyco electronics
Proposal Summary / Replace the existing clauses 7.1 and 7.2 with a new clause 7.1 that combines the tests in the existing clauses 7.1 and 7.2
Technical Rational for Proposal / The existing clauses 7.1 and 7.2 list distortion as a measure of protector performance at maximum voltage or maximum current, but they don’t say how to evaluate distortion. This contribution explains how to measure distortion. It also notes that the distortion at maximum rated voltage and at maximum rated current can be measured in the same test setup, and therefore the Maximum Rated Voltage Test and the Maximum Rated current Test can be combined into one test covering both.
Proposed Change or New Material / See following pages
WG Resolution / Accept/ Reject / Accept with Modifications

7.1 Rated voltage and rated current test

7.1.1 Background

Protectors are rated for maximum voltage and current. As the signal voltage or current is raised toward the maximum rated level, the protector may begin to distort the signal. Distortion shows up as harmonics of the signal. Distortion, often measured as total harmonic distortion (THD), is measured as a ratio of the power in the harmonics to the power in the fundamental. The formula used for this evaluation is:

(1)

Where:

%THD = Total Harmonic distortion as a percentage

Eh = voltage of harmonic h

Ef = voltage of the fundamental frequency

N = number of harmonics considered

The signal source generally has harmonics in it, so the THD of the signal generator needs to be measured, and subtracted from the measurements on the protector. Calling Es the voltage of signal generator harmonic s, and using the first 10 harmonics of the signal, the %THD of the protector [THDP] is

(2)

7.1.2 Purpose

The purpose of this test is to verify that the surge protector can be used continuously at a specified maximum voltage, current, and temperature without undesirable signal distortion or failure.

7.1.3 Equipment

(1) Spectrum analyzer with a frequency range of at least 1 – 10 kHz

(2) High impedance differential probe

(3) Signal generator capable of producing a 1 kHz signal

(4) Optional: Amplifier to boost the output of the signal generator to the specified voltage and current [likely, if ringing voltage is present].

7.1.4 Equipment States Subject To Test

  • Terminal pairs as specified in Figure 2
  • Biased
  • Unbiased
  • No load
  • A load resistance RL equal to the maximum rated voltage divided by the maximum rated current.

7.1.5 Procedures

  1. Select a test configuration from Figure 2 appropriate to the protector being tested.
  1. Connect the load RL to the output of the DUT, as shown in the selected configuration of Figure 2
  1. Connect the differential probes to the spectrum analyzer
  1. Connect the differential probes to measure the voltage across RL
  1. Connect the signal generator to the input of the DUT, as shown in the selected configuration of Figure 2. Note: If the signal generator is not capable of supplying the maximum rated voltage and current specified for the DUT, then an amplifier must be added to boost the input signal to the required levels.
  1. Place the DUT in an environmental chamber, and allow the temperature of the chamber to stabilize at the lowest rated temperature of the DUT.
  1. Set the frequency of the signal generator to 1 kHz.
  1. Set the signal generator output (or amplifier output, if an amplifier is needed) to the maximum rated voltage.
  1. Set the bias to zero.
  1. Use the spectrum analyzer to measure the amplitude of the fundamental and the first 10 harmonics, Eh
  1. Disconnect one side of the load resistance RL from the circuit
  1. Repeat step 10
  1. Repeat steps 6 – 12, but with the environmental chamber set at the highest rated temperature of the DUT
  1. If a configuration has been chosen that has more than one input or output [e.g. Configuration 4 (unbalanced) or 5 (unbalanced) in Figure2], select a combination of input and output that has not been tested, and repeat steps 2-13, until all possible combinations have been tested.
  1. Remove the DUT, and connect the spectrum analyzer and load RL directly to the signal generator [or signal generator plus amplifier] output.
  1. Use the spectrum analyzer to measure the amplitude of the fundamental and the first 10 harmonics, Es
  1. If the biased state is to be tested, apply the specified bias and repeat Steps 6 through 14.

7.1.6 Alternative Methods

None.

7.1.7 Suggested Test Data

  • Equipment state(s).
  • Leads tested.
  • Calculate the THD for each case tested, using equation (2) in clause 7.1.1

7.1.8 Requirements

  • The THD as calculated in clause 7.1.7 shall not exceed 1%[Note: The 1% limit was taken from the existing clause 7.2. Is it too stringent?]
  • No failure mode as defined in clause 9, shall occur.

7.1.9 Comments

  1. The measurement frequency was chosen to minimize power line harmonics, while at the same time minimizing the loss of harmonic amplitude due to the effects of shunt capacitance. Other frequencies can be used, but should be documented if they are.
  1. Step 10 measures the performance of the protector at maximum rated current
  1. Step 12 measures the performance of the protector at maximum rated voltage

A, A1, A2=ammeters or oscilloscopes with current shunts, for reading current A

C=common terminal

DUT=device under test

e, e1, e2=dc or sinewave sources with less than 1% total harmonic distortion, for providing voltage level e

RL, RL1, RL2, RS, RS1, RS2=noninductive resistors

X1, X2, Y1, Y2=signal terminals

Figure 2—Test circuits for the rated current test [Note: Needs to be redrawn]9

Note: Does leakage current need to be measured as part of the test where RL is disconnected?