موتور رژیم کاری S1 چنانچه بار مکانیکی آن از قدرت نامی موتور تجاوز نکند می تواند در هر رژیم دیگری کار کند. اصولاً رژیم غیر S1 به منظور یک انتخاب اقتصادی وقتی موتور حالت کار دائمی ندارد تعریف می شود و در این رژیمها موتور می تواند برای کوتاه مدت با توانی بیشتر از مقدار نامی خود کار کند.
DUTY CYCLE APPLICATIONS
TYPES OF DUTY
The duty cycle of a motor describes the energization/de-energization, and load variations, with respect to time for any given application.
Duty cycle applications may be divided into three basic classifications:
1. Continuous duty is a requirement of service that demands operation at an essentially constant load for an indefinitely long time.
This is the most common duty classification and accounts for approximately 90% of motor applications. To size a motor for a specific application with this duty cycle classification, select proper horsepower based upon continuous load.
2. Intermittent duty is a requirement of service that demands operation for alternate intervals of load and no-load; or load and rest; or load, no-load and rest; each interval of which is definitely specified. Select a motor for these applications to match the horsepower requirements under the loaded condition. In some instances, such as a hoist or elevator application, savings in the purchase price of a motor may be possible by designing for the intermittent duty cycle. 30 or 60 minute motors are normally specified. Frequent starts, however, can increase motor heating.
3. Varying duty is a requirement of service that demands operation at loads and for intervals of time, which may be subject to wide variation. For this classification of duty cycle, a horsepower versus time curve will permit determination of the peak horsepower required and a calculation of the root-mean-square (RMS) horsepower will indicate the proper motor rating from a heating standpoint. The following example demonstrates the method for selecting a motor for a varying duty cycle based upon peak horsepower and RMS horsepower requirements assuming constant frequency.