Type Tests for IEC 61010-1 Equipment

Cherie Forbes

Safety certification of laboratory, measurement, and control equipment requires that product designs pass a gauntlet of tests specified in the standard.

IEC 61010-1 is the safety standard for electrical measurement, control, and laboratory equipment.¹ That is equipment typically used in nonresidential environments. As described in its statement of scope, the standard covers the following:

• Electric shock.
• Mechanical hazards.
• Excessive temperature.
• Spread of fire.
• Effects of fluids and fluid pressure.
• Effects of radiation, including laser sources and sonic and ultrasonic pressure.
• Liberated gases, explosion, and implosion.

Manufacturers can meet the requirements of IEC 61010-1 by designing products with safety in mind, by selecting and using components within their ratings, by examining the finished product, and by testing it.

Two categories of tests are specified in this standard: routine tests and type tests. Routine tests are those that are conducted by the manufacturer on 100% of production to establish that each manufactured item complies with particular requirements. An example would be ground continuity tests performed to ensure that the enclosure is adequately grounded. Type tests are conducted by the safety-testing laboratory to determine whether a representative sample of the planned full production run complies with the requirements of the standard. This article outlines the most common tests conducted during type testing for safety certification of a product.

Before testing can begin, product ratings for electrical and environmental conditions must be established. The manufacturer must provide a complete set of manuals for installation, use, and maintenance. Type tests are conducted against the manufacturer’s ratings and instructions. Typically, equipment is evaluated with the following ratings:

• Indoor use.
• An altitude of 2000 m.
• A temperature range of 5° to 40°C.
• A relative humidity (RH) of 80%.
• Mains supply-voltage fluctuations of ±10%.
• The presence of typical transients on the mains supply (those of installation, or overvoltage, category II).
• Pollution degree 2.

However, it is not unusual to have ratings outside of these specifications. A rating that exceeds any of those just listed must be evaluated either by examination or by test.

This article does not describe all the tests in 61010-1, nor does it provide all conditions and specifications for each test. The intention is to provide a fundamental understanding of the types of tests that may be conducted by the test lab, and their purpose. For a comprehensive description of the tests, consult the standard.

Insulation Tests

Figure 1. A typical block diagram showing equipment insulation points (indicated by letters A–J).

Before any insulation-related test can be conducted on a piece of equipment, the test lab must draw a block diagram of the system (see Figure 1). Insulation between various parts of the equipment, such as the mains input circuit, low-voltage signal circuits, ground, and so on, must be classified according to the type of insulation required (basic, reinforced, etc.), and the working voltage across the insulation point must be measured. An insulation point may be a space between two traces on a printed wiring board, or it may be a physical barrier such as is found in an optocoupler.

The test lab then prepares a table giving the requirements for creepage distance, clearance, and dielectric-strength test voltage for each of the insulation locations. The test lab uses this table to evaluate the product.

After first measuring the creepage distances and clearances, the test lab conducts dielectric-strength tests. Any inadequate insulation within the equipment will be apparent from the results of these tests.

Next, the lab performs a humidity preconditioning test. The equipment is placed in a 40ÞC humidity chamber set for 92.5% ± 2.5% RH, or higher if the equipment carries an extended environmental rating. It sits unpowered in the humidity chamber for a period of 48 hours. After that interval, a technician removes it and allows it to rest for 2 hours before conducting dielectric-strength tests again. The purpose of this preconditioning test is to ensure that hygroscopic, or water-absorbing, materials have not been used for insulation.

Power Cord, Conduit, and Grounding Tests

Power-supply cords of the nondetachable type must be tested to ensure that the cord anchorage provides suitable strain relief. The anchorage must not allow strain on the cord and must protect the insulation of the conductors from abrasion. The test lab conducts a push-pull test in which the cord is pushed into the equipment and then quickly pulled out again, for a total of 25 cycles. This is immediately followed by a torque test, conducted at some level between 0.1 and 0.35 Nm (depending on the mass of the equipment), and a dielectric-strength test. This test reveals whether strain relief is adequate.

North American deviations from IEC 61010-1 apply in the case of conduit. Rigid conduit is installed in accordance with instructions, then pulled. A torque test and bending test also are performed on the conduit.

Tests of the continuity and impedance of all ground bond connections are part of the regimen. For 1 minute, a current of 25 A or two times the rated current of the equipment, whichever is greater, is applied between the protective conductor (ground) terminal and the part required to be grounded. North American deviations from the international standard require that this test be conducted either at 40 A or at two times the rated current of the equipment, if that is greater, for 2 minutes. There must be continuity in order for the current to flow, and the measured impedance must be low enough that it cannot exceed 0.1 Ω for plug-connected equipment or exceed 10 V across the test points for permanently connected equipment. (The latter limitation is 4 V for Canada.)

Mechanical Tests

Many tests are conducted on the equipment enclosure. The test lab carries out stability tests to ensure that the equipment will not topple over even in the most unfavorable conditions. All units of equipment other than handheld items are tilted by 10°. Equipment exceeding 1 m in height and 25 kg in mass, and all floor-standing equipment, is subjected to a force applied in various directions (except upward) to try to topple the equipment.

Drawers and doors accessible to the operator may be placed in the most unfavorable position during the test, which involves a force of either 250 N or 20% of the mass of the equipment. In addition, technicians apply 800 N of force downward on all horizontal working surfaces of floor-standing equipment, and on any other surfaces that provide a ledge less than 1 m above the floor. If the equipment overbalances during any of these tests, it is considered to have failed the test.

Handles and grips for lifting and carrying the equipment also need to be tested. Each handle or grip must be able to withstand a force of four times the mass of the equipment for 1 minute. Handles or grips shall not break loose, crack, or be permanently distorted as a result of this test.

Wall- or ceiling-mounted equipment must be installed following the manufacturer’s installation instructions and then tested. The mounting brackets must be found to withstand the weight of the equipment plus three times that weight for 1 minute. The bracket and mounting surface shall not be damaged by performance of this test.

The enclosure, intended to provide mechanical protection, must be shown to be unbreakable. A static test, dynamic test, and drop test are conducted to demonstrate this. In the static test, the test lab applies a 30-N force by means of a hard 12-mm-diameter rod that has a hemispherical-shaped end. The rod is addressed to every accessible part of the enclosure. Nonmetallic enclosures are tested only after the equipment has been operating for a while at its maximum rated temperature, or at 40°C, whichever is greater, because plastic enclosures can soften at elevated temperatures.

Performance of the dynamic test involves striking the enclosure with a 50-mm-diameter steel sphere with 5 J of energy. The test technician either applies the steel ball pendulum style, swinging it from a height of 1 m, or else drops the ball from a 1-m height. The enclosure may be placed on its side for this test. Nonmetallic enclosures are tested at their minimum ambient temperature rating, if this is less than 2°C, because plastic enclosures can become quite brittle at these lower temperatures.

There are several different drop tests that may be conducted with portable, or nonfixed, equipment. The corner-drop test is used for equipment less than 20 kg in mass. One corner of the product is raised 100 mm from a concrete or steel test surface, or to an angle of 30°, whichever is less severe, and then dropped. One drop is performed for each corner. The face-drop test is used for equipment between 20 and 100 kg in mass. It is similar to the corner-drop test, except that the front edge is raised either 25 mm or 30°, whichever is less severe, before the unit is dropped onto the surface.

Handheld and direct plug-in equipment items are exempt from the corner- and face-drop tests. They have their own test. In this, the test lab drops the equipment from a height of 1 m onto 50-mm-thick hardwood, which in turn rests on a rigid base such as concrete. The drop is conducted so as to have the equipment fall on its weakest side or edge.

For all of the drop tests, nonmetallic enclosures are cooled to their minimum rated temperature if this is less than 2°C.

Subsequent to mechanical testing, compliance is checked by examining the enclosure for cracks and openings that could allow hazardous parts to become accessible. These tests are followed by dielectric-strength tests to confirm that the insulation has not been impaired by subjection to the mechanical test regimen.

Temperature and Heating Tests

Temperature tests are conducted with the equipment installed as the manufacturer instructs and operating at its maximum configuration, meaning with all cards installed and drawing the greatest amount of power that would be drawn in normal use. Outputs are loaded to the maximum manufacturer specifications. Any duty cycle specified by the manufacturer is adhered to. The equipment under test is operated within a temperature chamber set for the manufacturer’s specified maximum ambient, unless that temperature is 40°C or less, in which case the product may be tested at room temperature. In this case, measured surface temperatures are adjusted by calculation to reflect testing at an ambient of 40°C.

Temperatures on a variety of components are monitored: on transformer and motor windings; on accessible surfaces, including any nonmetallic enclosures, knobs, and handles; on any component that has a maximum temperature rating that cannot be exceeded, such as electrolytic capacitors and printed wiring boards; and on field wiring terminal boxes. Testers generally apply thermocouples on the components, but either thermocouples or the rise-of-resistance method may be used with motor and transformer windings. The rise-of-resistance method compares the cold (before testing started) and hot (during testing) resistances of the winding with the ambient air temperature to determine the actual temperature of the winding. Rise-of-resistance is more accurate than the thermocouple method for testing windings because thermocouples can be applied only on the outer surface of the windings, which tends to run cooler than the inner windings.

Table I. Surface temperature limits in normal condition—Table 15 from IEC 61010-1, 2nd ed.

Temperature testing is usually conducted at the voltage tolerances; that is, if the equipment is rated 100–240 V, it will be tested at 90 V (–10%) and 264 V (+10%), or at the test tolerances specified by the manufacturer. Temperatures of each component are monitored throughout the test, and testing is terminated only after all of the component temperatures have stabilized (meaning that all components have reached their maximum temperature). Each component must not have exceeded its maximum temperature rating, and transformer windings and accessible parts cannot have exceeded the limits set out in IEC 61010-1, Tables 15 and 16, or the ratings provided by the component manufacturer (see Tables I and II).

Table II. Surface temperature limits of winding insulation material—Table 16 from IEC 61010-1, 2nd ed.

This test establishes that accessible parts are safe to touch and will not cause a burn—or, if the allowable surface temperature is exceeded, the part must be marked with the “hot surfaces” label as a warning to the operator. Also, the test verifies that the components inside the equipment are not reaching use temperatures above their rated levels. The test lab follows temperature testing with measurement of the creepage distances and clearances within the equipment to ensure that these have not been reduced by the elevated temperatures.

After the temperature test, nonmetallic enclosures are put in the oven either at 70°C or at a heat 10°C higher than the plastic temperature measured during the temperature test, whichever is higher, for 7 hours. The enclosure may be tested on its own or as part of the assembled equipment. Once the enclosure is removed from the oven, the mechanical tests performed on it earlier, as described above, are repeated to ensure that it does not now allow hazardous parts to become accessible.

The Effects of Fluids

Fluids may come into contact with the equipment in a variety of ways. Contact may be continual (such as via an internal vessel), occasional (such as the introduction of cleaning fluids), or accidental (such as coolant leakage). Each potential hazard must be evaluated to ensure that the fluid intrusion cannot compromise the insulation provided by the equipment.

Equipment is cleaned three times following the manufacturer’s specified cleaning instructions. Parts shall not be wetted if this would create a hazard. Another use for the cleaning test is to check the durability of any markings on the equipment. After the cleaning method has been applied, direct markings must remain legible and any labels should not peel off.

If liquid spills into the equipment during normal use (beverages are exempt), this should not be hazardous. Safety performance in this regard is tested by pouring 0.2 L of water from a height of 0.1 m over a period of 15 seconds onto each area of the product where liquid might enter.

When the equipment is designed to hold a container of liquid, overflow of the liquid should not create a hazard. Liquid containers are overfilled by 15% or by 0.25 L, whichever is greater, over a period of 60 seconds. Also, if the equipment is likely to be moved when holding a full container, the product being tested is tilted 15° in the most unfavorable direction with respect to spill potential. Compliance in relation to these fluid-hazard tests is demonstrated by conducting the dielectric-strength tests immediately after each fluid test is conducted, and determining that accessible parts cannot become a hazard.

It should also be noted that leakage pressure tests need to be conducted to ensure that any parts under pressure do not leak in the event of a greater pressure than normal, as specified in the standard. The standard has the particular test requirements.

The Effects of Radiation

Radiation as an influence needs to be evaluated, whether the equipment is exposed to radiation, such as ultraviolet (UV) wavelengths, or emits radiation via some operational component, such as a laser. In the exposure category, North American deviations from the specifications in IEC 61010-1 provide that nonmetallic parts that are subject to UV radiation must be tested if the failure of the plastic could result in a hazard.

With regard to emissions, tests are conducted to determine levels of ionizing radiation, microwave radiation, sonic and ultrasonic pressure, or laser radiation. The emissions most commonly tested or evaluated are sound pressure and laser radiation. Sound pressure must be limited to 85 dBA above a reference pressure of 20 µPa when measured at both the operator’s position in normal use and at a point 1 m from the enclosure. Laser and LED radiation must be evaluated in accordance with IEC 60825-1.²

Multimeters and Current-Measuring Circuits

A hazard must not occur when an incorrect combination of voltages and settings is applied. The test lab applies voltages for one set of terminals (for example, the voltage measurement terminals) to the incorrect terminals (perhaps the current measurement terminals). During this test, all combinations of controls are tried to determine that an electric shock, fire, arc, or explosion cannot occur. In addition to applying the voltage to the incorrect terminals and settings, the test technician may activate the selector switch while the voltage is applied to ascertain that no hazard occurs.

Figure 2. Measuring circuit for alternating current with frequencies up to 1 MHz and for direct current—Figure A.1 from IEC 61010-1, 2nd ed.

Current-measuring circuits must be tested with 10 times the maximum rated current for 1 second. This shall not create a hazard situation. Also, if the equipment contains a range-change switch in the measuring circuit, that switch will be made to change the maximum current 6000 times for purposes of test. The switch must not cause an electrical or mechanical breakdown during the test, or exhibit any undue pitting or burning of the contacts afterward.

Single-Fault-Condition Testing

Generally, single-fault-condition tests are left to the end of the testing process because these tests sometimes damage the equipment under test. Before conducting single-fault tests, manufacturers must evaluate the equipment in terms of identifying all of its accessible parts. The importance of determining which parts are accessible is that the voltage, current, and capacitance measurements of these parts cannot exceed specified limits during single-fault testing if the product is to be compliant.

Figure 3. Measuring circuits for alternating current with sinusoidal frequencies up to 100 Hz (a) and for direct current (b)—Figure A.2 from IEC 61010-1, 2nd ed.

Limits. During normal operating conditions, accessible parts should not exceed the following voltage-level limits, according to 61010-1: 33 V rms, 46.7 V peak, and 70 V dc. (For North America, the limits are 30 V rms, 42.4 V peak, and 60 V dc.) It is acceptable for a component to exceed these voltages, however, as long as it complies with the current and capacitance limits. The current limits are 0.5 mA rms, 0.7 mA peak, and 2 mA dc, as measured on the measuring circuits diagrammed in Figure 2 or Figure 3, as appropriate. The capacitance limit designated by line A in Figure 4 cannot be exceeded.

During single-fault conditions, these limits are higher. Voltages on accessible parts should not exceed 55 V rms, 78 V peak, or 140 V dc. (The corresponding North American limits are 50 V rms, 70 V peak, and 120 V dc.) Moreover, the voltages should not exceed the levels shown in Figure 5 when measured across a 50-kΩ resistor. Again, it is acceptable for these voltages to be exceeded as long as the current limits and capacitance limits are not. The current limits are 3.5 mA rms, 5 mA peak, and 2 mA dc, as measured using the measuring circuits diagrammed in Figure 2 or Figure 3, as appropriate. The capacitance limit designated by line B in Figure 5 cannot be exceeded.

Figure 4. Charged-capacitance-level limits in normal (line A) and single-fault (line B) conditions—Figure 2 from IEC 61010-1, 2nd ed.

Tests. For all of the following 12 single-fault tests, these limits have to be applied against each accessible part.

Test 1. A protective impedance providing insulation may be a high-integrity component, a combination of components, or a combination of basic insulation and a current- or voltage-limiting device. This protective impedance may have to be tested at this stage. A high-integrity component is evaluated separately; it is not necessary to conduct a single-fault test of it. The combination of components or combination of basic insulation and a current- or voltage-limiting device is tested by applying a short or disconnect across one of the components or the basic insulation, whichever is less favorable. Each of the components or the insulation may be tested with respect to multiple faults, but only one fault may be applied at a time.

Test 2. For the protective conductor test, the conductor (ground) is disconnected, except in the case of permanently connected equipment or equipment using an IEC 60309 connector for mains power. With the ground removed, accessible parts must meet the single-fault voltage, current, and capacitance limits.

Test 3. Equipment or parts designed for short-term or intermittent operation are to be run continuously, if possible. Individual parts such as motors, relays, and heaters are investigated under conditions of continuous operation.

Test 4. Motors are stopped while fully energized or else are prevented from starting, whichever produces the less- favorable result.

Figure 5. The maximum duration of short-term temporary accessible voltages in single-fault condition—Figure 1 from IEC 61010-1, 2nd ed.

Test 5. Capacitors in motor auxiliary winding circuits are short circuited, unless the capacitor is a self-healing type.

Test 6. Mains transformers must have each of their secondary windings short circuited and overloaded. In the short-circuit test, with all secondary windings loaded to their rated load, one secondary winding is short circuited. This is then repeated with all the other secondary windings.

For overload testing, the secondary windings are either loaded to their rated load or unloaded, whichever is less favorable. One secondary winding is overloaded by applying an adjustable resistor across the winding so as to draw the maximum allowable current for 1 hour. This is often limited by fuses, in which case the current characteristics of the fuse must be evaluated. Typically, fuses certified to UL 248-14 and CSA C22.2 No. 248.14 will allow 135% of the fuse rating for 1 hour, and IEC 60127–certified fuses will allow 150% of the fuse rating for 1 hour. However, this should be verified by the specifications for the fuses used. The fuse that is being overloaded generally is removed to ensure that it does not open and terminate the test before the end of the 1-hour period. This test is repeated with all the other secondary windings.

Test 7. All outputs must be short circuited one at a time.

Test 8. Equipment that may be powered from more than one source is simultaneously connected to both supplies, unless the construction does not allow this test.

Test 9. To test the cooling system, any air holes may be closed, cooling fans may be stopped, the circulating water or coolant may be stopped, and so on.

Test 10. In equipment that incorporates heating devices, these devices may be faulted by overriding the timers, overriding the temperature controllers, and simulating a loss of cooling liquid.

Test 11. Insulation between circuits and parts may be short circuited if the insulation falls short of the level specified for basic insulation. This includes any single-fault tests that are conducted on an unapproved power supply, such as shorting capacitors, diodes, and the like.

Test 12. To test interlocks, each part of the interlock system may be short circuited or open circuited, whichever is less favorable. These tests must show that the interlock cannot be defeated in a single-fault condition such that the result is to allow access to hazardous parts.

Special Considerations. All single-fault tests are conducted at the rated ambient temperature or 40°C, whichever is higher. The voltages of accessible parts must be monitored during the fault tests to determine that all accessible parts may be considered safe to touch. Temperatures of windings also must be evaluated during the tests to establish that they do not exceed their allowable temperatures. Moreover, the enclosure is to be wrapped in cheesecloth for these tests. If charring of the cheesecloth occurs, the compliance of the equipment is called into question.

Noncertified parts that are used for protection, such as a noncertified thermal cutout, may be bypassed or removed for the single-fault tests. These parts are not considered to be reliable and might not open when expected if the fault were to be repeated. A single-fault test in which a noncertified part has been relied upon for safety may be repeated three to five times.

All tests are held for 1 hour. If the temperature of the equipment has not stabilized at the end of 1 hour, or if the test is perceived to potentially cause a risk of shock, spread of fire, or injury to persons if the testing were to extend beyond 1 hour, the test may be continued to a maximum of 4 hours. The test is terminated when it is shown that no hazard can occur from the applied fault.

At the conclusion of the fault, the test technician applies the dielectric-strength test to all parts requiring reinforced or double insulation. The test voltage applied is only the test voltage for basic insulation, however. This ensures that if one level of insulation is faulted, one level of protection remains intact.

Conclusion

Many tests are conducted when an item of electrical equipment undergoes 61010-1 evaluation. The purpose of these tests is ultimately to ensure that the equipment will remain safe during intended use and under single-fault conditions.

Through careful testing and evaluation, the equipment will be shown not to be a shock hazard, not to contain mechanical hazards, not to get excessively hot, not to spread a fire, not to be affected by fluids and fluid pressure, not to be affected by nor to produce hazardous radiation, and not to produce gases that are liberated. Equipment that satisfies the test requirements is considered safe and may be placed on the market.

References

1. IEC 61010-1:2004, “Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use—Part 1: General Requirements,” 2nd ed. (Brussels: International Electrotechnical Commission, 2004).
2. IEC 60825-1:2001, “Safety of Laser Products—Part 1: Equipment Classification, Requirements, and User’s Guide” (Brussels: International Electrotechnical Commission, 2001).

Cherie Forbes is lab coordinator at M. A. Lamothe & Associates Inc. (Georgetown, ON, Canada). She can be reached at cherie@lamothe-approvals.com.