sensor technology:Power frequency sensor low frequency sensor design principle
Date:2015-05-21
Frequency sensor is commonly known as low-frequencyCurrent and voltage, switching power supply in order to show the difference between the high-frequency sensor, frequency sensor widely used in the past, the traditional power supply, and stable way these power supplies is the use of a linear regulator, so those traditional The power is also known as a linear power supply.
frequency sensor principle is very simple, theoretically relevant formula is not complicated, so we formed the view: too simple, it was three or four formulas, nothing to study . Just based on those simple formula, immediately successful design.
I think the understanding of both the above merits, but also a place worth studying. Merit: According to the calculation formula, you can quickly calculate the results, to solve the problem; the place is worth studying: do you know your own design product performance optimized design designed it yet how the economy
For an example, according to the power selected core size is a very complicated issue because more factors involved. Some books recommend using the following semi-empirical formula to select:
S = K · Sqrt (P) (1)
After the set S, and perform other calculations. This is indeed a practical way, but also recognize that this is a simplified design methods, in most cases there is a waste. This design approach for amateurs need not discuss (only occasionally to design a sensor own use), but for businesses, it is worth discussing, high-volume products with this design, reflecting lower economic efficiency.
? Well, in professional situations, such as sensor manufacturers, how they approach
on principle, based on the wire in the window to select the core specifications occupancy factor, but this calculation is very complicated, but the relationship is not simple, such as correlation calculation formula is:
P = 0.0222 · f · B · J · Sc · Sm (2)
when the current density is determined by the voltage adjustment rate, calculated as:
P = 0.0555 (f · f) (B · B) (Sc · Sc) · Sm · ΔU / (Z · Lm) (3)
this complex relationship, to artificial to come up with a design solution is very troublesome, so, experts on the actual situation, these relationships binding data compiled into a series of tables, the design engineer long based on different design specifications corresponding check table, you can get a set of practical data, such as look-up table according to the power and other indicators give the core specifications.
This method brings convenience is so large, so you can quickly come up with some solutions, combined with the accumulation of experience, the program can make the appropriate judgments, and then make optimization. Even so, this method there are two major shortcomings, first, the experts can not make all the campaign table, two engineers to come up with a more complete product design parameters, you have to spend a lot of time to go one by one calculation, the head engineer engage in several programs a day out certainly big. Fortunately, the current popularity of computer applications, specialized software has also been, you can let the computer do the calculations rigid, engineers only concerned with the design and optimization programs.
As another example, the current density for the selection, simple design is generally recommended as 2.5A ~ 3A / (mm · mm), but according to (3), the small power adjustment rate is large, the current density can be taken large, to achieve 8 ~ 9A / (mm · mm) [See column "will do low-EI-typeCurrent and voltage come in chat" posted, I was there to the landlord provides six programs], when the temperature is still small,Current and voltage safe work, this design in the premise of ensuring safety, generally reduce the amount of copper, at a very high price of copper, the lower the cost; while power adjustment rate limited, the current density may be less than 2A / ( mm · mm), the sensor temperature is too high or it may burn down sensor. It should be emphasized noted that not just the current density can be increased, and it is linked to indicators designed to calculate given just increase often leads to deterioration of performance, even burned sensor.
Some people may think: why did care about I do not think so, say foreign economic growth how how to save energy, conservation of raw materials, is not that just a little bit to pull out the efficiency of switching power supply?? come from, not also a little bit of research out of it? Now the truth of this, if you really engage frequency sensor manufacturing and design, we must do a good job their bank, find out their own work-related content. Imagine, a company product requires various types ofCurrent and voltage, want recruit engineers engaged in a design, to make a few examples of design on the spot, A and B are the results of two design engineers to meet the requirements, but the A's average cost of 10% lower than B, Who said that companies will hire you?
from the perspective of saving energy and raw materials, here to share with you:
1, reducing the amount of copper, there are two aspects can be achieved, one is to reduce the diameter which means that increased resistance of copper, copper loss loss will increase. Second is to reduce the number of turns, it will make no-load current increases, the same no-load losses will increase, if the sensor is in a standby power state for a long time, a waste of power resources is very large. Waste of electricity each year because of long-term household appliances in standby power is caused tens of millions of dollars.
2, the sensor should be designed so that the copper loss and iron loss equal to the lowest loss this sensor, working most stable, if a sensor design finished, due to save copper, while taking trumpet Wire and methods to reduce the number of turns, so that the core window there is a lot of space margin, so it shows too large core size selection, resulting in a waste core, because the core specifications, with a mean circumference of the winding also Great, it will also result in increased use of copper. According to current prices, the cost of the core is higher than the cost of copper.
So in the design, to ensure the performance to meet the customer's requirement, should try to choose a small core, can be 41, 48, would never use. About load current, saving standby losses from the consideration, or as low as possible is good.