Why the electric motor starts and stops: causes and how to fix it

In this article, we provide a description of jumps in an electric motor. You will understand why the electric motor starts and stops, We will show you the tools needed to detect faults in an electric motor and how to find the problem with possible solutions.

Electric motors start and stop due to various reasons such as circuit overloads, short circuits, poor ground wiring, faulty resistors, overheating, contamination, vibrations, faulty wiring, clockwise or counterclockwise rotation of the nose, fuses, cut-off programming, poor wiring insulation, incorrect values in the HMI (Human Machine Interface) or SCADA (Supervisory Control and Data Acquisition Software), power supply, etc.

This article is intended to help electromechanical and industrial plant maintenance technicians detect and resolve issues that cause an electric motor to start and stop. The 10 simple steps we are going to explain will make it easier for you to detect these issues. These tests apply to all types of electric motors.

Tools required to detect faults in an electric motor 

In order to find the reasons/cause/problem that cause an engine to start and stop, you must have some tools and equipment to perform tests. In addition to pliers, screwdrivers, and wrenches, you must have the following:

• Digital multimeter.
• Voltmeter.
• Insulation tester.
• Megger resistance tester.

Before I explain how to determine why an electric motor starts and stops, there are certain things I think you should know so that you have a better understanding.

No matter what type of electric motor you choose from the market, each electric motor has a service life ranging from approximately 30,000 hours to approximately 40,000 hours of use. You can find this information in the motor catalogues or specifications. The motor's service life is determined by the maintenance it receives, with its life being shorter without maintenance.

You should be familiar with what a breaker or circuit breaker is, as they are commonly used in industry. A breaker or circuit breaker is used to protect and control an electrical circuit. These breakers can be automatic or manual. A breaker is the main device that protects your entire electrical installation and your machine, as it cuts off the flow of electricity when there is too much electrical flow or a power surge. The circuit breaker cuts off the flow of electricity to prevent overheating and further damage.

Imagine the situation: if there were no breaker, the circuit would overheat or there would be a short circuit, and the common causes would be fires.

There is no doubt that having the power supply cut off by a breaker makes it safer, but it can sometimes be frustrating if the breaker constantly cuts off and restores the power supply. This may be due to a problem and should be fixed.

Why does an electric motor start and stop?

Engineers and technicians working in different industries, factories, electricity companies, water treatment and irrigation plants encounter various problems with electric motors that start and stop. These problems can be minor or serious. An electric motor starting and stopping may be due to a bad connection, poor timing, or weather conditions such as excessive heat causing the breaker to cut off the power supply.

It is also due to poor choice of breaker, connectors, and wiring, which do not meet the requirements for a proper installation to prevent the electric motor from starting and stopping.

How to find the problem of why the electric motor starts and stops

By following these steps and tests, you will be able to find the reason for the problem that is causing the electric motor starts and stops, Once the problem is identified, fixing it is a matter of minutes.

1. Check the continuity of the wiring using the digital multimeter.
2. Check the rotation of the electric motor, clockwise or counter-clockwise.
3. Check the values of the timer, date, and data.
4. Check the relays. If it is connected in a Star Delta configuration and is overheating due to the ambient temperature, the motor is being forced or because the motor is rotating in the opposite direction to normal.
5. Check the watertightness of the motor, if it is submersible.
6. Check whether the automatic switch or breaker has the correct settings to support the load.
7. Check the HMI values if it is connected to the HMI and PLC.
8. Check the fuses if the connection is Star Delta.
9. Check the insulation of the wiring.
10. Check the power supply.

How can we solve the problem?

Now I will explain each one in detail. If you read each step carefully, I am sure you will be able to solve the problem of the electric motor starting and stopping.

Wiring continuity check

In this step, engineers and technicians must check the continuity of the wiring using a digital multimeter.

This is a very important test, as it allows you to determine whether there is continuity in the wiring or whether there is a short circuit.

Check the continuity of the wiring with the digital multimeter by setting it to the tone function. If the wiring is fine, you should hear a BEEP, which indicates that the cable is fine.

If the cable is very long and you cannot connect the multimeter probes to the ends of the cable, you can connect a 10k resistor to the ends of the cable, and at the starting end, you can connect the multimeter to the resistor.

If you can read the values on the resistor, then the cable is fine and you can turn on the electric motor if there are no further problems.
 

Direction of motor rotation

In this step, engineers and technicians can check the direction in which the motor shaft rotates, whether it is clockwise or counterclockwise. If it rotates counterclockwise, it means that the motor is not working properly, as this can lead to overheating and permanent damage. Due to the counterclockwise rotation of the motor, the pressure of the liquids is slow.

This problem can be solved by changing the direction of the cables connected to the electrical panel.

If the electric motor turns clockwise, it means that it is working properly, which can be checked by the water pressure. Good water pressure indicates that the motor is working properly.

Timer adjustment

If your electric motor is connected to a timer for protection, you must check the values. If they are correct and the electric motor starts and stops, you must check the amperage of your motor, which is indicated on the motor plate. If your motor is 5A, all you have to do is calibrate the regulator to 5A with a screwdriver.
Remember to exceed the amperage indicated on the motor plate, as the electric motor will be damaged.
Check the motor relays. If the electric motor continues to start and stop due to the weather, check the heat of the relay with your hands and replace it if it is very hot.

Submersible motors

If the type of motor you are using is submersible (a submersible motor is one that is completely submerged in water or another substance), and the electric motor starts and stops constantly, you should check the cleanliness of the water or liquid.

When a submersible motor is used for sewage, the electric motor may suffer from starts and stops due to dirt.

When plastic or dirt causes the motor to jam, the breaker trips, cutting off the power supply.

In normal situations, if the motor becomes clogged with dirt, it will continue to run until it overheats and trips the breaker. In a situation like this, if there is no breaker to protect it, damage to the motor is imminent.

Breaker adjustment (automatic switch)

Breakers and contactors are designed to protect electrical installations. Once you have purchased an electric motor and know its specifications, a controller and protection system are easy to design.

You can order a breaker with the rating specified in the motor specifications.

The most common recommendation is that it should exceed the nose value by 10%, as the electric motor exceeds its rating when starting up, so it is advisable to protect against this excess.

If the electric motor still starts and stops, you can perform the test mentioned in the previous point or the following one. If, after performing the tests, the breaker continues to trip, there is no other option but to replace the breaker.

If the motor is connected to an HMI in a PLC or SCADA, you can change the values if they are too low or too high as stipulated by the motor.

Star connection – motor triangle 

If the motor is installed in a star-delta configuration, for added protection, check the fuses and replace any that have blown. But how can you tell if a fuse is working properly? With the digital multimeter set to Ohms or continuity, place the terminals on the ends of the fuse. If you hear a BEEP, it means that the fuse is fine. If you do not hear anything, it means that the fuse has blown and you must replace it with a new one.

Insulation test

Checking the insulation of the wiring is also important because when the weather changes from cold to hot, the cable heats up more than normal, which leads to the electric motor starts and stops, causing the load values to change even more; when the load is greater, the cable heats up more. This means that engineers must choose the right type of cable with the appropriate insulation to ensure that the electric motor works properly, avoiding starts and stops. To check the cable insulation, you can use the Megger Tester. If you want to know more about Insulation faults in electric motors: how to measure and fix them Subscribe to our newsletter.

Power supply

This is another important test that we must perform and know the specifications of the motor. You must know whether the motor you are going to use is single-phase or 3-phase.

You must know the specified voltage and the voltage you are using. If the power source is greater than that specified in the motor, then the breaker is likely to trip.

If the supply is lower or higher, it will cause the motor to start and stop. The specific voltage is written on a plate that comes with the motor. If it is single-phase, connect the motor to 210V-230V; if it is three-phase, connect the motor to 400V-450V.

So that's all there is to know about the problem of electric motors starting and stopping, its causes, and how to fix it. I hope you've learned something from this article. If you want to know more about Common faults in electric motors and how to fix them Subscribe to the technology newsletter for industry.