Drives and Control Solutions

Motors, Control Solutions, Power Transmission and Advanced Motion Technology                                                                 

February 18, 2020

By Mike Keefe

When selecting a motor, it is important to consider the required duty cycle to ensure the motor can meet the needs of the application.  

Knowing what type of duty cycle your motor requires will help a motor manufacturer like KEB select the best motor for your application. Watch the video below to see the most common types of motor duty cycles.

 

 

 

The International Electrotechnical Commission (IEC) defines eight classifications for duty cycle which are grouped by continuous, short term, or periodic cycles.  These cycles refer to the sequence and durations in time of all aspects of a typical operation, including starting, running with no load, running with full load, electric braking, and rest.  These operations are viewed by how they affect the motor temperature in order to determine if the selected motor is correct for the application, if increased cooling such as a forced ventilation fan is required, or if a whole new motor should be used.Motor-Duty-Cycles_Continuous-Operation.jpg

Continuous Duty

The first, and simplest, type of motor duty cycle is continuous duty.  This is also referred to by its abbreviated name, S1 duty.  In this type of operation, the motor runs with a constant load for a long enough duration so that it reaches thermal equilibrium.  This also assumes the starting of the motor can be considered to have a negligible effect on the motor temperature.  An example of S1 duty would be a fan that is switched on and then let to run non-stop.

Motor-Duty-Cycles_Short-Time-Duty.jpgShort Time Duty

The second type of motor duty cycle is short time duty. Similar to continuous duty, this operation runs with a constant load. Unlike continuous duty, it is shut off before it reaches thermal equilibrium. The motor is then allowed to rest long enough for it to reach ambient temperature. Short time duty is designated by S2 followed by the number of minutes in the cycle (S2 30 minutes).

Periodic Duty

Periodic duty refers to the designations S3-S8. These include cycles with and without rest that have starting, electric braking, and/or changing speeds/loads. Throughout all of these designations, the various operations of the cycle are repeated over time and the motor is not allowed to reach thermal equilibrium.

IMotor-Duty-Cycles_Intermittent-Periodic-duty-graph.jpgntermittent Periodic Duty

Intermittent periodic duty is the simplest type of periodic duty. This sequence of identical cycles each contain a period of constant load and a period at rest. This is very similar to S2 duty, but differs because it never reaches ambient temperature during its rest period. This duty cycle is abbreviated as S3 followed by the percentage of time under load.

An example of intermittent periodic duty could be a conveyor that runs at constant intervals with the same loading.

Continuous Operation with Electric Braking

Motor-Duty-Cycles-S3-duty_Small.jpgThe final example of motor duty cycle is continuous operation with electric braking.  This cycle includes a sequence of starting, constant load, and electric braking.  Motor-Duty-Cycles_Continuous-Operation-with-Electric-Braking.jpgAdditionally, there is not time during the operation for rest.  This type of duty cycle is abbreviated as S7 followed by the moment of inertia of the motor and load (Jm and JL).

The other periodic duty cycles S4-S6 and S8-S9 are similar to S3 and S7, but can be done with or without rest, starting, braking, and loading.

Conclusion

When purchasing a motor, it is important to consider the required operation and declare the duty cycle. There are many types of motors and gearing combinations that can be offered for your specific application. When you let a motor manufacturer know exactly the type of duty the motor can expect, you can ensure the proper motor will be selected for your application.

Source


Editor's Pick: Featured Article


BrakingResistor1When designing a motor control system, it is not always clear if a braking resistor is required and, if it is, how to proceed in selecting a braking resistor. This post is intended to simplify that process so it is clear when and how to select a braking resistor for your application. 

Why are braking resistors necessary?

Braking resistors are introduced into a motor control system in order to prevent hardware damage and/or nuisance faults in a VFD. They are required because in certain operations, the motor controlled by the VFD is acting as a generator and power is flowing back towards the VFD, rather than towards the motor. 

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           Partnering For The Next Step                

Siemens CanadaWelcome to the Digital Enterprise Virtual Summit brought to you by Siemens

How quickly can you react to changing conditions and demands in your market? How can you ensure your production will run securely at any time in the future?

Industry’s digital and technological transformation is the answer for meeting today’s and tomorrow’s challenges and market needs.

With the right digitalization and automation solutions, expertise won from practical experience, and a partnership approach that benefits all involved parties.

To explore these possibilities, we’re bringing together top-level speakers, specialists and decision-makers from various industries and experts from Siemens

to the Digital Enterprise Virtual Summit under the motto “Partnering for the next step.”   

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Motor Feature


S6 VFD for Linear Motor ApplicationsThe Combivert S6 drive is a modern, compact and flexible servo amplifier that can be used across a wide range of applications. The drive controller provides optimum performance in torque, speed, and position control. The S6 has the ability to control AC induction motors, AC PM motors, and lastly linear motors. In this article, we will be focusing on linear motors and how they work, as well as the simplicity of controlling them with the Combivert S6.

 

 

 

 

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