What is SELV?
Safety Extra Low Voltage (SELV) is a safety standard that specifies the maximum voltage limit for electrical devices to ensure safety from electric shocks.
According to the International Electrotechnical Commission (IEC) standard 60950, SELV is typically defined as an electrical supply that has a voltage of no more than 60V DC or 42.4V AC peak.
Generally, most switch-mode low voltage AC-DC power supplies with outputs of 48 VDC meet the SELV and its Applications requirements.
With a 48 V output, the OVP setting can only be up to 120% nominal, allowing the output to reach 57.6 V before the power supply shuts down.
This would still conform to the maximum 60 VDC for SELV power.
Requirements for SELV Circuit
A SELV circuit must have:
- Protective separation either as double insulation, reinforced insulation or in protective screening from all circuits other than SELV
- Requires simple separation from other SELV systems and the ground.
On the other hand, the safety of a SELV circuit is provided by
- Extra-low voltage
- Low risk of accidental contact with a higher voltage
- Lack of a return path through the earth that an electric current could take, in case it comes in contact with a human body.
SELV and its Applications in Real-World
SELV and its Applications can be commonly seen where human safety is a primary concern, such as in medical equipment, control systems, and electric vehicles.
In electric vehicles, SELV is used to power low-voltage systems such as lights, sensors, and communication systems.
This ensures that in the event of an accident or damage to the high-voltage system, the low-voltage systems remain safe and do not pose any risk of electric shock to the occupants of the vehicle.
In electric vehicles, SELV is typically provided by a separate 12V battery or by a DC-DC converter that steps down the high-voltage battery voltage to the SELV level.
The 12V battery is used to power the vehicle’s low-voltage systems, such as the headlights, radio, and other electronic devices.
SELV and its Applications apply in electric vehicles that enable the use of standard wiring and connectors, which can help to reduce the cost and complexity of the vehicle’s electrical system.
Additionally, the use of SELV and its Applications can help enhance the reliability of the vehicle’s electrical system by reducing the risk of electrical shorts or other malfunctions that can occur when high-voltage and low-voltage systems are mixed.
In real-world applications, SELV is an important safety standard that is used in a wide range of electrical and electronic devices. It is particularly important in applications where the risk of electric shock is high, such as in medical equipment, control systems, and electric vehicles.
By limiting the voltage of electrical devices to a safe level, SELV and its Applications help to ensure that these devices are safe to use and do not pose a risk to the user’s health or safety.
Companies Leveraging SELV and its Applications
Some of the companies that use SELV and its Applications in their products include:
Siemens
Siemens is a multinational company that produces a range of electrical and electronic products, including medical equipment, control systems, and power distribution systems, all of which use SELV and its Applications to ensure safety.
ABB
ABB is a leading manufacturer of power and automation technologies, including DC-DC converters, which are widely used in industrial automation and renewable energy systems.
Delta Electronics
Delta Electronics is a Taiwanese company that produces a range of power electronics products, including DC-DC converters, which are used in many applications, including electric vehicles, renewable energy systems, and telecommunications.
Philips Healthcare
Philips Healthcare has a wide product portfolio that includes a range of medical devices, like patient monitors, ultrasound machines, and MRI scanners, all of which use SELV and its Applications for safety requirements.
Schneider Electric
Schneider Electric produces a range of electrical equipment, including circuit breakers, switches, and transformers, using SELV and its Applications to ensure safety.
Bosch
Another multinational engineering and technology company, Bosch provides a wide range of products, including automotive components, power tools, and home appliances, all of which use SELV to ensure safety.
General Electric (GE)
GE offers a range of electrical and electronic products, including power generation equipment, lighting, and control systems, hence utilizing SELV and its Applications for safety purposes.
Fujitsu
Fujitsu is a multinational information technology company that produces a range of products, including laptops, servers, and storage systems, all of which use SELV to ensure safety.
Emerson Electric
Emerson Electric produces a range of products, including power supplies, control systems, and HVAC equipment, thus ensuring the safety using SELV and its Applications.
Honeywell
Honeywell is a multinational conglomerate that produces a range of products, including aerospace systems, building automation, and industrial control systems.