What Happens if You Overvolt a Motor? & How To Protect It


Electric motors convert electrical energy to mechanical energy, used in many applications and devices. However, each motor has specific ratings, such as voltage and current ratings, so can overvolting damage the motor?

Can Overvolting Damage Motor? And How to Avoid it?

Yes, overvolting can damage the motor because the excessive voltage and current flow through the motor and overload its components which causes damage to the motor’s parts and insulation, and the life of the motor will be reduced. You can avoid overvolting the motor by decreasing the voltage source to the motor’s limit.

What Happens if You Overvolt a Motor?

What will happen is that excessive voltage will be created when you overvolt a motor, and an excessive current will flow through the motor. The new load put on the motor can cause damage to its components and affect the motor’s insulation; this will reduce the motor’s life.

If you raised the supply voltage above the motor or equipment’s voltage rating, you would overvolt the motor. Overvoltage can be caused for many reasons, such as the power source bad regulation from an oversized transformer.

Another reason that can cause overvoltage is varying or uneven circuit loading, isolation failures or electrical insulation, and wiring errors.

How To Protect The Motor From Overvoltage?

The three-phase monitor relay is the best way to protect the motor from overvoltage because it’s cost-effective, has easy installation, and protects the equipment and motor from overvoltage conditions.

Phase failure relay, also known as Macromatic’s three-phase monitor relay, protects the equipment and the devices from premature equipment failure by observing common fault conditions like overvoltage.

A three-phase monitor relay can send notifications to any fault case and enable you to control equipment and devices, where you can turn them off before any damage happens. This relays fast and quick troubleshooting.

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How To Check Electric Motors?

To check your motors, you need to test their components like their shaft, bearing, fan, and motor windings. In addition, you can use a multimeter to test the motor’s power and its windings.

The Shaft and The Bearings

One of the most common components that go bad over time is the bearings; they need to be replaced after a while due to the tear and wear. When used without replacement, Worn-out bearings can reduce the motor’s efficiency.

Another result of using worn-out bearings is the damage and the failure of the mechanism of the motor.

The Motor Windings

You need to check the resistance of the motor windings and inspect if there is any wear or tear in the windings as they are very important for the motor’s mechanics. To test the motor’s winding, you will need a multimeter and follow these steps:

  1. Adjust the multimeter to ohms and test the terminal and wire of the motor.
  2. Test the windings shorts or open and for short to ground.
  3. For short to ground test, adjust the multimeter to ohms and disconnect the motor’s power source.
  4. Test each wire; the wires with issues will have 0 ohms or infinity reading.
  5. If you find any wires with any issues, you should consult a professional to solve the problem.
  6. For open or shorts testing, you should test T1 to T3, T2 to T2, T1 to T2, and T2 to T3; some motors can have other markings such as U or W or V; always check your motor’s manual.
  7. The readings should be between 0.3 to 2 ohms; if you have 0 readings, you have shorts in your windings.
  8. If you have read more than 2 ohms, you have open winding, which means that you have a broken wire in your winding.

The Motor’s Fan

The fan is used in motors to keep its temperature cool and prevent it from experiencing heat problems, which means the fan is a very important component in any motor. However, fans can be clogged with debris and dust; therefore, you need to check them regularly.

The debris and dust can reduce the airflow, keeping the heat, increasing the motor’s temperature, and affecting its performance. The motor’s fan must also be properly secured to work, move, and cool down the motor.


What Are The Ratings And Specifications of Motors?

There are several characteristics that you should be considering when choosing and connecting a DC motor, such as input and output characteristics:

Input Characteristics

Input characteristics or ratings are the ones that determine the electrical characteristics of the motor, for example:

The Operating Voltage

Motors that use batteries as the power or voltage source need fewer batteries to achieve the required voltage; therefore, low voltage ratings are more preferred and desirable than high voltage ratings.

However, when using a piece of electronic equipment to drive an motor, you will find them more efficient at higher voltage ratings. The DC motor function at a wide range of voltage from 1.5 volts to 100 volts.

The motors used to operate roboticists use low voltages like 6, 12, and 24 volts because these roboticists operate using batteries.

The Operating Current

The perfect motor is supposed to generate a great amount of power using a low amount of current; however, the current and the voltage rating are great indicators of the motor’s output capacity.

Meanwhile, the voltage times current, known as the power input, is a great indicator of the motor’s mechanical power output; the more torque the motor provides, the more current it needs.

Therefore, the current ratings are not determined until the motor is stalled because it will be applying its maximum torque and drawing its maximum current. For example, a low voltage “12 voltages” draws 1oo mA current.

Output Ratings

Output ratings are the ones that determine the output characteristics of the motor, for example:

The Speed

When the motor is running freely or unloaded, you can determine its speed or the rotations per minute, also known as RPM, according to its specified operating voltage. DC motors’ average speed is between one to twenty thousand RPM.

A LEGO pulley wheel or mounting disk can be used to determine the speed of the motor with one hole on the motor. An oscilloscope and a slotted optical switch measure the time between the switch openings.

The Torque

The motor’s output shaft produces the rotary force, known as the torque. The maximum torque of the motor is produced when the motor is stalled. Therefore, the torque rating is determined when the motor is completely stalled and called stall torque.

The English system measures the torque in ounce-inches; meanwhile, the metric system measures the torque in Newton-meters. The small motors’ torque is measured milli-Newton-meters (mN-m) or 1/1000 of an N-m; torques ratings range from one ounce-inch or less to large motors in many dozen ounce-inches.

The Power

The product of the motor’s torque and its speed is the power; the motor’s maximum output is achieved at the moment between the stalled state (no speed, maximum torque) and the unloaded speed (no torque, maximum speed).

The output power can be calculated through a simple equation which is RPM * Torque / 9.57.


To sum up, when you overvolt a motor, an excessive voltage will be created, and an excessive current will flow throw the motor. In addition, the new load put on the motor can cause damage to its components and affect the motor’s insulation, reducing the life of the motor.

The overvoltage happens when you raise the supply voltage above the motor or equipment’s voltage rating. It can also be caused for many reasons such as the power source bad regulation from an oversized transformer.

To protect your motor from overvoltage conditions, you should use the three-phase monitor relay because it’s cost-effective and has easy installation. In addition, it protects the equipment and motor from overvoltage conditions.

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