1.Ratings
There are two kinds of rating for motors: continuous duty rating and short time rating classified by the temperature rise of motors. Usually they are defined by power output, voltage, cycles in frequency, and rpm
etc.:so-called rated power output, rated voltage, rated cycles in frequency, and rated rpm.
2.Continuous duty rating and short time rating
Continuous operation at the rated output power under normal condition is called a continuous duty rating.
While operation at the rated output power in a specific time is so called short time rating.
3.Output power
The twist force produced by motors in an unit time shall be expressed by rpm and the torque of motors. The rated output power of a motor is expressed by Watt in Japan and H.P. in Europe.
（W）= 1.027×0.00001×T ×N where
1.027×0.00001 : a constant T(gcm) : Toruqe N(rpm) : number of revolutions per minute
4.Rated output power
Rated power output means to develop a best characteristic output power under the rated voltage and rated frequency of motors. The rpm torque is simply called rated output power.
5.Starting torque
Torque produced at any instant of a starting motor is called starting torque. Motor is not rotating in case of a larger load than the torque.
6.Stop torque
The maximum torque is produced any motor under a specific voltage and specific frequency. Any loading is applied on a Motor within this range of torque, motor is stopped.
7.Rated torque
The speed reduction gearing under rated voltage, rated frequency, rated power output is defined as continuous torque, as well as the rated torque, torque for rated rpm.
8.Rated rpm
The most favorable rpm of the motor shall be a rpm under a rated output power.
9.Rpm in synchronism
Suppose the number of poles of a motor and the frequency of power source are given. It can be sown in the following equation which is usually expressed by revolution per minute.
Ns=120f/p(rpm)
Where Ns=Number of rpm in synchronism
F=number of frequency in Hertz. P=number of poles of the motor 120=constant
For example:
A four-pole motor and frequency of the power source is 60Hz.
Ns=120x60/4=1800(rpm)
10.Slide slip rate
Another kind of indication for rpm can be shown in he following formula:
S=Ns-N/Ns or N=Ns(1-S)Ns:
Where Ns: rpm in synchronous(rpm)
Where N: rpm under any loading(rpm), The slide slip rate for a 4 pole 60Hz induction motor is, Revolution per S=0.1 N=120-60/4 (1-0.1)=1800(1-0.1)=1620(rpm)