the term "nominal capacity" we are confronted almost daily.Choose whether kettle or bulb - everywhere you specify this value.Units are in watts or kilowatts.It would seem - what could be easier in this matter?After all, since the school physics course we all know that to determine the power (P) is sufficient to multiply the value of current and voltage.But what lies behind the words "rated capacity"?
the term "nominal" refers to a specific value of anything, do not take into account external factors corrective.Thus, the rated power - the value specified by the manufacturer, which can be obtained only if the specified design parameters.This is a general concept.In each case the need to take into account their specific features.Here is an example with an incandescent lamp.On its glass flask noted: 230, 100 watts.That is, 100 W can only be achieved at a voltage of 230 V Rated power - these are the 100 watts.Its value decreases with a decrease in voltage and increases with increasing as these options are directly related to each other (P = I * U).
Typically, for most appliances there is a restriction on the upper limit, typically 5-10%.In other words, the work is permissible at 230 V + 23 = 253 W. The lower limit can not be specified, as in the case of the lamp.More sophisticated equipment nameplate parameters limited in both the top and bottom.
For example, how to understand the term "rated engine power"?There are two equivalent definitions - one in terms of electricity, and the other based on the estimated mechanical load on the shaft.Although they are directly linked, the latter is more simple to understand.We present two.On the nameplate are always set to power.It is numerically equal to the consumption from the mains at the design of mechanical load, the temperature of the housing must be within permissible limits (assuming continuous operation).That is, it can be assumed that the value is equal to the nominal passport.If the drive operates in the intermittent mode (PV is not equal to 100%), then this line is not satisfied, because the time is not enough work to go in steady state when the heating is compensated by an increase in ambient temperature.In this case, the need to load the schedule: the rated power is equal to the product of the values of the passport P and the square root of the ratio chosen schedule.All of the above is true for the electrical component.
According to another definition, the rated power is assumed to be a mechanical, developed by the engine at the rated voltage and temperature conditions, the corresponding passport.Thus, if the voltage (U) decreases, and the moment of force is changed while the rotational speed of the shaft can remain unchanged.As mentioned, the product manufacturer is laid in a certain "safety margin": oscillations of U in the range of ± 5% allows the engine to develop the current time (at constant frequency network).For the frequency of such reserve amounts to only 2.5%.
But the nominal capacity of the transformer takes into account only the temperature regime.If you look in the passport unit, there are shown two temperatures: the nominal and the surrounding air.If the former does not exceed its rated value, and the second data differs slightly from the passport, in this mode transformer rated power outputs.Any increase in the electrical load causes an increase in current and temperature, so it is quite enough control of the latter.As in the case of engines allowed a slight excess.
