Test Equipment

EMCPro™ 1089 Offered by Thermo KeyTek
3-Terminal Bellcore GR-1089-CORE 1st & 2nd Level Lightning Surge Tester

EMCPro™ Offered by Thermo KeyTek
Advanced, combination, low-cost EMC immunity test system with up to 7 compliance-level capabilities for testing for the CE Mark and Beyond

ECAT™ Offered by Thermo KeyTek
Expert Computer Aided Test system for ESD, EFT, Surge and Dips and Interrupts testing to Bellcore, UL, IEC, ANSI, etc. requirements.

Dips and Interrupts Background

Dips and interrupts can occur on the AC power mains as a result of a fault in the distribution system such as an open circuit breaker or a sudden large load being turned on in the immediate vicinity. A power distribution system fault can cause a switch in the distribution grid to open and close a number of times, resulting in multiple interrupts to electrical and electronic equipment.
Electronic products are tested for immunity to dips and interrupts to insure their continued reliable operation if subjected to dips and/or interrupts on the AC power mains. The European Union’s EMC Directive mandates dips and interrupts testing for virtually all electrical and electronic products as a condition for obtaining the CE Mark before shipping products to member states of the European Union.

Applicable Standards

Generic Immunity Standards, Product Standards and Product Family Standards require that dip and interrupt tests be performed in accordance with Basic EMC Standards: IEC 61000-4-11 and EN 61000-4-11. Thermo KeyTek’s Application Note, “EMC Standards Overview,” provides an overview of European Standards for electromagnetic compatibility, describes how the Standards relate to one another, and lists sources for procuring copyrighted documents.
1 IEC 61000-4-11 and EN 61000-4-11 are virtually identical standards.

Basic EMC Standard

The Basic EMC Standard for Dips and Interrupts defines methods of generating consistently reproducible electrical dips and interrupts for test purposes. They specify characteristics of the AC mains to the EUT such as peak inrush current, transition times and durations. While the Basic EMC Standard specifies how to perform Dips and Interrupts testing, the Generic, Product and Product Family Standards specify the test levels and pass/fail Performance Criteria.

Test Levels
 

Peak Inrush Current

IEC 61000-4-11 requires the simulator be capable of supplying peak inrush currents of up to 500A for 220V to 240V mains, and up to 250A for 100V to 120V mains. Additionally, the Standard requires this capability be measured using a bridge rectifier connected via a switch to a discharged 1700µF capacitor. The parallel discharge resistance should be chosen to allow several RC time constants between tests. An example in Annex A (normative) uses a 10k ohm resistance, providing a time constant of 17 s, “...so that a wait of 1.5 to 2 minutes should be used between inrush drive capability tests.”

The test for inrush current is performed by switching the generator from 0% to 100% at both 90Þ and 270Þ to insure sufficient peak inrush current drive capability for both polarities.

Waveform Verification

IEC 61000-4-11 requires that the simulator output be verified periodically. For Dip and Interrupt test simulators, it is necessary to verify the voltage transition levels, transition times to 100%, and the inrush current capability. Most modern oscilloscopes are capable of observing the voltage levels and transition times. For verifying the inrush current, a bridge rectifier, suitably rated 1700µF capacitor and appropriate current transformer are required.

Test Execution

According to IEC 61000-4-11, tests must be performed in compliance with the manufacturer’s test plan, which shall specify:
• Input power of the EUT
• Performance Criteria
• Operation modes of the EUT
• Test set-up description
• Type of designation of the EUT
• Information on possible connections, cables, peripherals, etc. After each group of tests, a complete functional test must be performed.

EUT Performance Criteria

For Dip and Interrupt tests, Performance Criteria varies in some standards depending on the duration or severity of the dip and/or interrupt. Under some conditions, loss of function is allowed, provided that the function is self-recoverable or can be restored by the control operations. Under less severe conditions, degradation of performance is allowed during the test, however, the unit must continue to operate as intended after the test. Refer to the tables located in the Generic, Product and Product Family Standards for specific Performance Criteria. The product cannot become unsafe under any conditions.

Dip and Interrupt Simulators

Dip and Interrupt Simulators produced by Thermo KeyTek meet all the simulator requirements of IEC 61000-4-11, including those for peak inrush current. Additionally, Thermo KeyTek simulators meet the fast switching time requirements not only to 100% as required by the standards, but from any level to any other level.