What is Motor Duty Cycle and S1 S2 S3 S4 on motor?


If you are connected with electrical, then you must have heard the name of motor duty cycle, because this question is many time asked in interviews and electrical exams. So this question becomes very important.

Also, if you have seen a motor in the industry or in your home at the plate of a motor, then it is written S1, S2 S3, or S4. times You may think that some motors have S1 written on them and some motors have S2, S3, or S4 written on them, so what is the mean of this?

So in today’s post, we will understand S1 S2 S3 S4 along with motor duty cycle very well. So let’s understand both questions one by one.

What is Motor Duty Cycle?

Friends, if we first talk about what is the duty cycle of a motor, then its meaning is simple. We all know that different motors are used for different tasks.

Like some motors have to run for a very long time, apart from this we also have some motors which will run for a few hours, then stop for 10-15 minutes and then run back for a few hours. Along with this, there are some motors that run for a few hours or a few minutes then off for the rest of the day.

So, friends different motors have to be installed for different applications. For different applications we have to use which motor, we know from its duty cycle.

Friends, from duty word you will clear that if a person has a duty of 5 hours in the office, then it means that he has to work for 5 hours in the office. Similarly, friends, for how many hours the motor will work, it is the duty of the motor.

Meaning that from duty cycle, we can tell whether our motor will run for 24 hours or our motor can run only for 8 hours. So all this can be told from the duty cycle of the motor.

Friends, you must have been very clear about the motor duty cycle that is how many hours the motor can work, it is its duty cycle. Now let us talk that S1 S2 S3 S4 is written on the motor, what does it mean?

What is the mean S1 S2 S3 S4 on Motor?

Friends, although you have to keep in mind that there is a total of S1 to S10 in the market, but most of the S1 S2 S3 S4 motors are used in the industry. Almost the entire motor is covered in these motors. So friends, without much delay let’s understand one by one where which motor is used?


S1: Friends, if you see motors in the industry, most of the motors are of S1 type. Because friends S1 type motor is designed in such a way that once we start it, this motor can run for a few days or even a few months without getting damaged.


If we need such a motor in the industry, which has to run for many months without stopping, then we use S1 type motor there.

Because the insulation of S1 type motor is designed in such a way that even if the motor runs for a long time without shutting down, the insulation will not damage. Therefore, S1 type motor is used in the industry so that even if the motor runs without stopping for months, its insulation will not be damaged.

S2: S2 type motor is called “short time running motor”. If S2 is written on a motor, then it cannot be run for a long time. As in our homes, the motor installed at the water pump is S2 type. In most the cases this type of motor is run only for some time and then it turns off. From here you must have been completely clear that whatever S2 type motor we have, we can run it for some time only. Otherwise its winding may be damaged.s2-type-motor

S3: In such a place where we have to run the motor in periodic path or in cycle order like the motor has to run for 1 hour then stop 15-20 minutes then start again and in this way, the motor will continue run. For example, the compressors used in our industry are in load condition for some time and then turn off again, after some time start again. So, in this case we use S3 type motor only.s3-type-motor

S4: Friends, like S4 type motor, S3 type motor stays ON for some time and then OFF for some time. But the different thing comes in this that if we want high starting torque. Mean when motor is starting then we want high torque then we use S4 type motor. If we talk about example then you can see it in your crane. Because in crane we need high starting torque.


We hope friends that you have learned what the duty cycle in motor and what the mean of S1 S2 S3 S4. If any question is left, you can comment below or send the question to us on Instagram Electrical Dost.”

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Aayush Sharma is an Assistant Engineer in a Semi-Government Company and Owner of "Engineering Dost" and the Electrical Dost YouTube Channel. He Provides you Engineering inquiry and support of engineering market facts with Practical experience.


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