In recent years, there has been a trend to upgrade household and similar appliances with electronic controls. For these types of products, this represents a significant change because they have previously employed “low tech” controls, including components such as electromechanical thermostats, thermal overprotection devices, and mechanical switches. Electronic controls have a potential to be interfered with which may cause inadvertent operation and related safety hazards.

Amendment 1:2004 to the EN 60335-1 safety standard, which covers household and similar appliances, added EMC requirements to address these concerns. The severity of these new EMC requirements is much higher than previous levels. In addition, while the previous requirements only included monitoring of appliance performance, the new requirements also include monitoring the appliance for hazardous operation. These Amendment 1 requirements specifically apply to electrical appliances which incorporate protective electronic circuits, those which have a switch with an off position obtained by electronic disconnection, and those with a switch that can be placed in a stand-by mode electronically. These requirements became mandatory on Oct. 1, 2007.

The new requirements significantly increase the IEC 61000-4-x severity levels mandated in the more typical EMC Standard EN 55014-2.

Enlarge this picture Fig. 1. Flowchart assists in the process of determining which appliances may fall within the new requirements.

The increased severity levels for applicable products are as follows:
IEC 61000-4-2 Electrostatic Discharge (ESD)

• +/- 15 kV (air).
• +/- 8 kV (contact).

  IEC 61000-4-3 Radiated Susceptibility

• 10 V/m.

  IEC 61000-4-4 Electrical Fast Transients (EFT)

• +/- 4 kV (AC).
• +/- 4 kV (DC).
• +/- 2 kV (I/O’s).

  IEC 61000-4-5 Surge

• +/- 2 kV Differential Mode (line-to-line).
• +/- 4kV Common Mode (line-to-ground).

  IEC  61000-4-6 Conducted Radio Frequencies (RF)

• 10 V rms (AC).
• 10 V rms (DC).
• 10 V rms (I/Os).

  IEC 61000-4-11 Voltage Dips/Interrupts

• Dip of 20 percent for 5 sec.
• Dip of 30 percent for 500 ms.
• Dip of 60 percent for 200 ms.
• Interrupt >95 percent for 10 ms.
• Interrupt >95 percent for 20 ms.

  IEC 61000-4-13 Harmonics/Interharmonics.

• Now applicable.

  For clarity, a comparison of the typical to the increased severity levels can be seen in Table 1. In addition, a flowchart (Fig. 1) is also provided to assist in the process of determining applicability.

Enlarge this picture Table 1. Comparison of the typical to increased severity levels.

A protective electronic circuit is defined in the EN 60335-1 standard as an electronic circuit that prevents a hazardous situation under abnormal operating conditions. And, an electronic circuit is a circuit with at least one component in which conduction is achieved principally by electrons moving through a vacuum, gas or semiconductor. In order to determine if an appliance has this type of circuit, one needs to find out whether there are any electronic circuits in a product that function to prevent any type of hazard. One example of where testing would be required is an electronic controller that monitors temperatures within an appliance and turns off the appropriate circuit, or the complete unit, in response to excessive temperatures. Unless the controller has been tested to these increased severity levels, which is unusual, the appliance would need to be tested to these higher levels.

An appliance with switches, with an off position obtained by electronic disconnection, would also be tested to these higher severity levels. In order to determine if an appliance has this type of switch circuit, one needs to know how the off position is obtained. If a separate and isolated mechanical switch is used, then this more severe testing is not necessary, unless an electronic circuit is used to initiate and close this switch. One example of where testing would be required is a membrane switch that turns the unit off by electronically sending a signal to other circuitry.

If an appliance has switches that can be placed in a stand-by mode electronically, it should also be tested to these higher severity levels. To determine whether an appliance has this type of switch circuit one needs to know how the stand-by mode is obtained. If a separate and isolated mechanical switch is used, then this more severe testing is not necessary. For example, an electronic controller that has a membrane switch that sends a signal to other circuitry to put the unit into a stand-by mode would require testing.

In order to determine applicability, the basic main question that should be asked is whether there are electronic circuits in an appliance that can be susceptible to external electromagnetic interference that could result in a hazardous condition. If so, then the appliance should be subjected to testing at these higher severity levels. All appliance modes should also be evaluated. As a result of this testing, the appliance should not undergo any dangerous malfunction, the protective electronic circuits should not fail, and appliances with an applicable off switch or stand-by mode should not become operational.

Since there is no grandfather provision, manufacturers of household and similar appliances should immediately have their products evaluated, and potentially tested.  This will assure that manufacturers of such products are prepared for the latest EN 60335-1 EMC test requirements.