Brownout (electricity)
A brownout is a drop in the magnitude of
Unintentional brownouts can be caused by excessive electricity demand, severe weather events, or a malfunction or error affecting electrical grid control or monitoring systems.[1][2] Intentional brownouts are used for load reduction in an emergency, or to prevent a total grid power outage due to high demand.[3] The term brownout comes from the dimming of incandescent lighting when voltage reduces.
In some countries, the term brownout refers not to a drop in voltage but to an intentional or unintentional power outage (or blackout).[4][5][6]
Effects
Different types of electrical apparatus will react in different ways to a voltage reduction. Some devices will be severely affected, while others may not be affected at all.
Resistive loads
The heat output of any resistive device, such as an electric
Motors
Commutated electric motors, such as universal motors, will run at reduced speed or reduced torque. Depending on the motor design, no harm may occur. However, under load, the motor may draw more current due to the reduced back-EMF developed at the lower armature speed. Unless the motor has ample cooling capacity, it may eventually overheat and burn out.
An
Power supplies
An unregulated DC supply will produce a lower output voltage. The output voltage ripple will decrease in line with the usually reduced load current. In a cathode-ray tube television, the reduced output voltage will make the screen image smaller, dimmer and fuzzier.
A linear DC regulated supply will maintain the output voltage unless the brownout is severe and the input voltage drops below the drop out voltage for the regulator, at which point the output voltage will fall and high levels of
A switched-mode power supply will be affected if the brownout voltage is lower than the minimum input voltage of the power supply. As the input voltage falls, the current draw will increase to maintain the same output voltage and current, until such a point that the power supply malfunctions or its under-voltage protection kicks in and disables the output.
Digital systems
Brownouts can cause unexpected behavior in systems with digital control circuits. Reduced voltages can bring control signals below the threshold at which logic circuits can reliably detect which state is being represented. As the voltage returns to normal levels the logic can latch at an incorrect state; to the extent that even '
See also
- Black start
- Dumsor
- Power outage
- Undervoltage lockout(UVLO)
- Voltage drop
References
- ISSN 2073-4433.
- ISBN 0-920650-00-7.
- ISBN 978-0-470-12987-6.
- ^ "Beijing 'Brown-out' to Save Power". BBC News. July 22, 2004.
- ^ Burgos, Nestor P. Jr. (November 7, 2010). "Iloilo Power Firms Asked to Explain Brownouts". Philippine Daily Inquirer. Archived from the original on June 5, 2013. Retrieved June 21, 2012.
Both Peco and PPC were asked to submit their explanations on the power interruptions being investigated by Gerochi's committee.
- ^ Baxendale, Rachel (January 26, 2019). "Heatwave: AEMO Hits Go on Emergency Energy Supply Measures as Victoria Swelters". The Australian. Retrieved January 30, 2019.