What is Undervoltage – A Guide

Undervoltage can be loosely defined as when a voltage (mostly in 3-phase power systems) is way below the recommended/intended levels. These systems have an Undervoltage relay that prevents the circuit-breaker from closing; hence the motor, for example, won’t start. The relay thus protects the motor from possible damage if/when voltage is lost or reduced drastically.

Is Undervoltage Bad for Electronics?

While it might seem harmless at first, Undervoltage is quite harmful to electronic components and the motor as well. Although the motor might be able to start, it won’t work as efficiently and effectively as it is designed (due to altered voltage pulses), causing increased wear and tear. In other words, Undervoltage could have a severe impact on your electronics’ lifespan.

Why Is It Referred to As a Brownout?

Brownout is the term used to describe the dimming of lights when there’s a voltage drop. Voltage may sag due to a disruption in the electrical grid and could also be imposed to reduce the risk of a total blackout. Brownouts may also be affected to reduce the load on the gridline as well.

What is a Minimum Voltage Relay?

relay board

Every coil has a minimum operating voltage, also known as an Operate Voltage, which is needed for it to work as desired. The minimum voltage relay only activates when the said voltage is reached and remains on for as long as the operating voltage is maintained.

How Can I Protect My Equipment from Overvoltage?

There are several measures you can undertake to protect your electricals from overvoltage. One of the most straightforward and commonly used safety measures is using a fuse at the input supply. The fuse can only allow a preset voltage to pass through. It thus will blow if there’s overvoltage to protect the rest of the equipment. Fuses, however, only provide one-time protection and will need to be replaced when/if blown.

What Is An Undervoltage Release, And How Does It Work?

This device is usually (though optional) installed in the circuit breaker to trigger a power trip in case of an Undervoltage. However, the device isn’t powered through the circuit breaker, which allows it to provide additional protection. This device is commonly set from between 35 and 70% of the UV rating for optimal protection.

How To Know If a Motor Is Overloaded?


One of the best ways to do this is to check the current going into the motor using an ammeter. Compare the readings with the nameplate to see if it matches or is too high.

Does A Manual Starter Have a Low Voltage Protection?

A manual starter lacks the LVP (Low Voltage Protection). Low voltage protection is meant to prevent the equipment from restarting in case of a power failure. In its absence, power contacts remain closed in a manual starter (if switched ON), leaving it unprotected. However, some motors may have or use an AC magnetic motor starter.

Causes Of Undervoltage in Generators?

A voltage drop may occur when the prime mover speed is too low. Undervoltage may also happen as a result of a ground fault in the generator’s field winding. A short circuit in the stator winding or a poor connection or small brush contact surface may also be a reason for Undervoltage in generators.

What Is A 52 Relay?

This is a device designed to interrupt or close an AC power circuit when there’s a fault, during emergencies, and even in normal conditions. A 55-power factor relay activates when the AC circuit falls below or rises below the predetermined value.

Causes Of Voltage Surge or Overvoltage?

Overvoltage can occur as a result of switching impulses of the system and lightning impulses. Although lightning is one of the leading causes of voltage surges, factors such as insulation failure, resonance, and arcing ground could be to blame as well.

What is Overvoltage?

Overvoltage is a situation where the supply voltage rises, surpassing the motor/equipment’s rated input voltage. This happens if there’s varying/uneven circuit loading, oversized transformers, electrical isolation or insulation failures, and poor regulation by the power utility company.

How To Protect Your Equipment from Overvoltage?

You can use Transient Voltage Surge Suppressors and Surge Arresters to protect your equipment from overvoltages. Having a TVSS or arrestor helps restrict only the specified voltage to pass through. You could also use this for under voltage protection. 

Which Devices Are Used for Overvoltage Protection?

A Silicon Controlled Rectifier (SCR) or a thyristor is used to protect power supply units from overvoltage. The SCR detects high voltage, which triggers the thyristor to short circuit, preventing the high voltage from passing through.

Will A 5v Relay Work On A 3.3 V?

A 5V relay can work on a 3.3V relay. This is because the 3.3V is seen as a logic high, allowing for a low current data connection. While the relay will work, you may need an input of the same voltage (5V) to ensure it doesn’t fail.

What Is the Minimal Voltage Needed to Switch A Relay?

Most relays have a rating of 12V, though they can operate with a little under 12V up to 15V comfortably.

This is one of the reasons most of your car accessories will be on when the engine is off but the key ON. The relay will still switch when the voltage is low, such as when the lights are ON, and the engine is off.

Will a 24-volt Relay Work on 12V?

24V relay

Most 24V relays should work satisfactorily on 12V. Anyone looking for a low-side switch can thus use 24V dc relays without any trouble. All you’d need to do is connect Fig,1 to a 12-13.8v DC rail.

Is It Advisable to Unplug the Fridge in The Event of An Undervoltage/Brownout?

It’s highly advisable to unplug your fridge, freezer, air conditioner, furnace, and water if there is a brownout. The best way to do this would be to turn the breakers off until power is restored and safe to turn them back on. Be sure to label the breakers to prevent others from ‘accidentally’ turning them ON again.

Can I User My Computer During A Brownout?

Computers are sensitive to power fluctuations and won’t handle brownouts nicely. Brownouts could ruin your computer power supply or even the motherboard, a reason you should turn it OFF and unplug it, if possible, to prevent damage or data loss. Like most electronics, computers work on a specific voltage, which must be maintained to ensure it runs smoothly without risking anything.

How Long Does a Blackout Last?

Depending on your location, a blackout should typically last one hour. However, some areas, such as police stations, airport control towers, hospitals, and fire departments, aren’t subject to blackouts. Power companies will progressively switch off supply in certain areas, leaving others connected to avoid huge losses.

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