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電機(jī)啟動(dòng)型熱敏電阻器
馬達(dá)啟動(dòng)用正溫度系數(shù)熱敏電阻器，只要用于電冰箱、空調(diào)馬達(dá)啟動(dòng)、空調(diào)變頻機(jī)啟動(dòng)、馬達(dá)過熱保護(hù)等。
工作原理：馬達(dá)啟動(dòng)器是利用PTC陶瓷的電流－時(shí)間特性，當(dāng)電壓施加于PTCR時(shí)，開始有大電流I流過，經(jīng)過一定時(shí)間ts后，隨著PTCR溫度的升高，電阻值迅速增大，導(dǎo)致電流也急劇下降，這段時(shí)間ts可以從0.1s到幾秒，其值取決于PTCR的熱容量、電阻值、熱耗散條件、負(fù)載電阻及工作電壓，當(dāng)外電壓撤銷時(shí)，PTCR將冷卻至常溫電阻值。利用這個(gè)原理，在家用電冰箱和空調(diào)機(jī)等電器馬達(dá)啟動(dòng)上得到了廣泛的使用。應(yīng)該說明，當(dāng)使用PTCR的延遲性能時(shí)，如果要重復(fù)同一延遲時(shí)間，應(yīng)間隔一定時(shí)間tr（即所謂的恢復(fù)時(shí)間），使PTCR恢復(fù)到原始狀態(tài)溫度，所以應(yīng)避免立即重復(fù)動(dòng)作，否則PTCR不能提供持續(xù)的大電流，使壓縮機(jī)無法正常啟動(dòng)工作，會(huì)導(dǎo)致壓縮機(jī)燒毀。
電機(jī)在啟動(dòng)時(shí)，要克服本身的慣性，同時(shí)還要克服負(fù)載的反作用力（如冰箱壓縮機(jī)啟動(dòng)時(shí)必須克服制冷劑的反作用力），因此電機(jī)啟動(dòng)時(shí)需要較大的電流和轉(zhuǎn)矩。當(dāng)轉(zhuǎn)動(dòng)正常后，為了節(jié)約能源，需要的轉(zhuǎn)矩又要大幅度下降。給電機(jī)加一組輔助線圈，只在啟動(dòng)時(shí)工作，正常后它就斷開。將PTC熱敏電阻串聯(lián)在啟動(dòng)輔助線圈， 啟動(dòng)后PTC熱敏電阻進(jìn)入高阻態(tài)切斷輔助線圈，正好可以達(dá)到這種效果.
產(chǎn)品優(yōu)勢(shì)：采用帶有PTCR的啟動(dòng)電路具有經(jīng)濟(jì)、可靠、電路簡(jiǎn)單等特點(diǎn)，優(yōu)于過去的重錘式啟動(dòng)電路，它具有無觸點(diǎn)、低噪聲、高可靠、長(zhǎng)壽命等特點(diǎn)。
PTC Thermistors for Motor-Starting
Applications
Motor-starting PTC Thermistors are mainly used in fridge and air-conditioner motor-starting, air-conditioner transducer-starting, motor over-heating protection.
Working Theories
Motor-starter is a machine that makes use of the PTC pottery current-time feature. When PTCR is put on by pressure, the heavy current begins to pass through, and after certain time, with the increasing of the PTC temperature, resistance value goes up sharply and cause current to fall down suddenly. During this time, ts can change from 0.1s to several seconds. The specific time depends on PTCR’s heating capacity, resistance value, heating dissipation condition, overloaded resistance and operating voltage. When the outer electricity pressure retreats, PTC will become cool and alter to normal resistance. Making use of this theory, PTC is applied extensively in household refrigerator and air-conditioner motor-starter and so on. One point should be noticed that when using the delay-time feature of PTC, we should make the PTC recover to its original temperature every certain time tr（That is what we called recovering time）. So sudden repeated movements should be avoided, otherwise PTC cannot provide constant heavy current, and the compressor cannot start or work normally, which will cause the compressor burnt.
When the electricity motor is being started, it has to overcome its inertia and the counterforce of loading （eg: Its counterforce must be overcome when refrigerator compressor starts）, so starting the electricity motor needs relatively heavy current and torque. When it runs normally, and the torque needed has to be brought down to save energy. Give motor electricity a circle assistant loop, and it works only when the motor starts and it will break up after the current goes regularly. This effect can be reached by connecting the PTC Thermistor in series in starting assistant loop and cutting off the assistant loop when PTCR enters the state of high resistance.
Advantages
The starting circuit with PTC owns the feature of being economic, reliable, simple which is better than the heavy hammer starting circuit Additionally, It has the characteristics of being contactless, lower noise, high reliability, long service and so on.
