Device for protecting the electric motor from overheating. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electric motors
Comments on the article
Protection of electric motors against current overloads is carried out by thermal relays built into magnetic starters. In practice, there are cases of failure of the electric motor due to overheating at the rated current value, at elevated ambient temperatures or difficult heat exchange conditions, while thermal relays do not work.
The proposed device for protecting the electric motor from overheating, shown in the figure, allows you to turn off the electric motor when its windings overheat, regardless of the reasons that caused this overheating.
The device consists of a thermistor R3 temperature sensor, fixed in the motor housing as close as possible to the windings, and an electronic relay on the VT1 transistor, installed in the magnetic starter casing.
The operating mode of the transistor VT1 is set by a variable resistor R5, and it is closed until the temperature allowed for the motor is reached. Relay K1 in the collector circuit VT1 is de-energized and its contacts are closed. The power supply circuit of the magnetic starter winding is on. When the motor overheats, the resistance of the thermistor R3 decreases, which causes a voltage change at the base of VT1. It opens and relay K1 is activated, turning off the power to the winding of the magnetic starter KM 1. The electric motor is turned off. The motor can only be switched on again after it has cooled down.
Establishment The device is reduced to setting the threshold for operating an electronic relay with a variable resistor R5.
Details. Thermistor type MMT-1, relay type K1 RES-9 (passport RS524.201), capacitor C1 type MBGO 1 μx400 V, capacitor C2 type K50-12 200μx300V.
Author: V.F. Yakovlev, Shostka
See other articles Section Electric motors.
<< Back
Latest news of science and technology, new electronics:
Air trap for insects
01.05.2024
Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>
The threat of space debris to the Earth's magnetic field
01.05.2024
More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>
Solidification of bulk substances
30.04.2024
There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>
| Random news from the Archive NEC's thinnest 15,6" ultrabook
19.12.2012
NEC is proud to announce that its LaVie X (code LX850/JS) is the thinnest ultrabook to date, featuring a 15,6-inch 1920 x 1080 Full HD IPS screen with LED backlight.
The model is enclosed in a case with dimensions of 375 x 255 x 12,8 mm and weighs 1,59 kg. It is built on an Intel Core i7-3517U processor and is controlled by the Windows 8 operating system.
Even in the arsenal of the computer is: 4 GB of RAM; 256 GB solid state drive;
Wireless network adapter Wi-Fi 802.11b/g/n; Bluetooth 4.0 + HS module; 2 megapixel webcam; Slot for SD/SDHC/SDXC memory cards; Two USB 3.0 ports and an HDMI port.
|
Other interesting news:
▪ paper battery
▪ Self-constructed systems
▪ All the gold in the world
▪ Reading the minds of jellyfish
▪ Set a speed record
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ section of the site Interesting facts. Selection of articles
▪ article Freeze the worm. Popular expression
▪ article Who is Napoleon? Detailed answer
▪ article Why compass readings can be unreliable. Children's Science Lab
▪ article Rationale for choosing a modern oscilloscope. Encyclopedia of radio electronics and electrical engineering
▪ article Entertaining experiments at home. Encyclopedia
Leave your comment on this article:
All languages of this page
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua
2000-2024
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese