Motors Applications

It depends upon the application, the details of which have been withheld from the forum.

https://www.engineeringtoolbox.com/iec-duty-cucles-d_739.html

<...due to non availability it will take a month to replace...> Only if the supplier doesn't value the level of business that is being conducted. Getting someone from the buying function onto the case, in order to expedite, would seem like a good idea, as a threat to take the business elsewhere can do wonders to clear log-jams. Escalate it.

yeah mine was continuous duty whereas S4 was intermittent periodic duty.

but i want to run the S4 motor for continuous duty application.

what was the worst damage can happen if i operate S4 instead of S1?

The <...worst damage can happen...> is that it will burn out.

<...yeah mine was continuous duty whereas S4 was intermittent periodic duty.

but i want to run the S4 motor for continuous duty application...> This information was stated in the original posting and there is no need to repeat it.

One might wonder why the motor was not rejected at any pre-despatch inspection that took place or upon arrival.

Yes, there are many under explained layers to this motor misapplication.

Good question.. hardly off topic.
Either the vendors dispatch should have caught it or goods receiving!

If someone else made the mistake, tell them they owe you a correctly specified motor and run this one until it arrives as payment for your trouble, then let them decide if they want it back (if it holds up).

if YOU made the mistake and you cannot return this motor, order the new one and run this one to destruction, hoping that is not going to happen until after the correct one arrives.

Continuous duty is not necessarily or always the most severe application. Frequent restarts, especially jogging or plugging, can be worse.

You might need to run your motor continuously, but will it be fully loaded all the time? If not, you might be O.K., but it could be worth discussing with the motor mfr.

Big difference.S1 are continuous duty,S4 are not.

Here is a link that explains the difference in types,with graphs.

https://electrical-engineering-portal.com/10-duty-types-three-phase-asynchronous-motors

The problem is that the S4 motor is for periodic duty while the S1 is for continuous duty. The running of an intermittant rated motor continuously is the heat build up in the windings from the copper and iron losses and the inability to remove the heat will cause insulation and winding failure and most likely in a very short time which could be less than a day.

My advice from experience is don't even contemplate running the S4 motor in continuous duty S1. Return the motor to the supplier and get one from someone who has read the specifications on your order and can supply an S1.

Remember motors are driven by smoke and once the smoke escapes the motor is dead.

I think you can use the S4 duty motor as S1 if-in order to not overload the motor and the maintain the same relative thermal life expectancy [see IEC 60034-1 Annex A] you may reduce the load.

Since the temperature rise in a motor is proportional to the losses the total equivalent current will be Ieq=sqrt((I1^2*t1+I2^2*t2)/Tc) where:

Ieq = continuous load duty S1 equivalent current; I1 is the constant load current multiplied by t1 the time in which I1 is acting, I2 is the starting current and t2 is the starting time. Tc it is one cycle load time. Translated in power units:

Peq=Prated*sqrt((t1+(Ist/Irated)^2*t2)/Tc)

In my opinion for Tc=10 minute t1=2 sec and (Ist/Irated)=8 for 25% 30 hp S4 19hp it could be S1 equivalent

However, the manufacturer has to declare what is the real equivalent S1 duty power for the delivered S4 duty motor.