Mai samar da na'ura mai jujjuya birkin mitar yana tunatar da ku cewa a cikin tsarin sarrafa saurin saurin mitar, ainihin hanyar rage saurin shine a hankali a rage mitar da aka bayar. Lokacin da inertia na tsarin ja ya yi girma, raguwar saurin motar ba zai ci gaba da raguwar saurin motar da ke aiki tare ba, wato, ainihin saurin injin ɗin ya fi saurinsa na aiki tare. A wannan lokacin, jagorar layukan filin maganadisu da aka yanke ta hanyar jujjuyawar injin ɗin ya yi daidai da na yau da kullun na aikin injin ɗin. Jagorancin ƙarfin lantarki da aka jawo da kuma na yanzu na jujjuyawar juyi shima ya saba da na jujjuyawar motsi, kuma motar za ta haifar da mummunan ƙarfi. A wannan lokacin, injin ɗin shine ainihin janareta, kuma tsarin yana cikin yanayin haɓaka birki. Ƙarfin motsi na tsarin ja yana dawowa zuwa bas ɗin DC na mai sauya mitar, yana haifar da ƙarfin wutar lantarki na DC ya ci gaba da tashi har ma ya kai matsayi mai haɗari (kamar lalacewa ga mai sauya mitar).
Ƙa'idar aiki na naúrar birki
Naúrar birki ta ƙunshi babban transistor GTR da kewayar tuƙi. Ayyukansa shine ƙara kayan aikin birki na waje don haɓaka yawan amfani da makamashin lantarki da aka sabunta lokacin da ma'aunin mahaɗin na yanzu ba zai iya adanawa a cikin kewayon ƙarfin lantarki da aka ƙayyade ko kuma na'urar birki ta ciki ba zai iya cinye ta cikin lokaci ba, wanda ke haifar da wuce gona da iri a ɓangaren DC.
In certain applications, rapid deceleration is required. According to the principle of asynchronous motors, the greater the slip, the greater the torque. Similarly, the braking torque will increase with the increase of deceleration rate, greatly shortening the deceleration time of the system, accelerating energy feedback, and causing the DC bus voltage to rise rapidly. Therefore, the feedback energy must be quickly consumed to maintain the DC bus voltage below a certain safe range. The main function of the braking unit system is to quickly dissipate the energy (which is converted into thermal energy by the braking resistor). It effectively compensates for the disadvantages of slow braking speed and small braking torque (≤ 20% rated torque) of ordinary frequency converters, and is very suitable for situations where fast braking is required but the frequency is low.
Due to the short-term operation of the braking unit, which means that the power on time is very short each time, the temperature rise during the power on time is far from stable; The interval time after each power on is longer, during which the temperature is sufficient to drop to the same level as the ambient temperature. Therefore, the rated power of the braking resistor will be greatly reduced, and the price will also decrease accordingly; In addition, due to the fact that there is only one IGBT with a braking time of ms level, the transient performance indicators for power transistor turn-on and turn off are required to be low, and even the turn off time is required to be as short as possible to reduce the turn off pulse voltage and protect the power transistor; The control mechanism is relatively simple and easy to implement. Due to the above advantages, it is widely used in potential energy loads such as cranes and in situations where rapid braking is required but for short-term work.
The function of the braking unit
1. When the electric motor decelerates under external force, it operates in a generating state, producing regenerative energy. The three-phase AC electromotive force generated by it is rectified by a three-phase fully controlled bridge composed of six inverter specific energy feedback units and freewheeling diodes in the inverter section of the inverter, which continuously increases the DC bus voltage inside the inverter.
2. When the DC voltage reaches a certain voltage (the starting voltage of the braking unit), the power switch tube of the braking unit opens and current flows through the braking resistor.
3. The braking resistor releases heat, absorbs regenerative energy, reduces motor speed, and lowers the DC bus voltage of the frequency converter.
4. When the DC bus voltage drops to a certain voltage (braking unit stop voltage), the power transistor of the braking unit is turned off. At this time, no braking current flows through the resistor, and the braking resistor naturally dissipates heat, reducing its own temperature.
5. Lokacin da wutar lantarki na bas din DC ya sake tashi don kunna na'urar birki, sashin birki zai sake maimaita tsarin da ke sama don daidaita wutar lantarkin bas kuma tabbatar da aikin yau da kullun na tsarin.