產(chǎn)品細(xì)節(jié)介紹
1VCF752000操作面板主機(jī)
電機(jī)數(shù)據(jù)表規(guī)定，允許的啟動(dòng)順序?yàn)?冷或1熱，之后必須等待5小時(shí)嘗試再次啟動(dòng)。
?這意味著在正常啟動(dòng)條件下，電機(jī)使用34%到50%的熱容量。因此，兩個(gè)允許連續(xù)啟動(dòng)，但不允許三次（即34×3>100）。
?如果熱/冷曲線(xiàn)或熱/冷安全失速比不可用，程序0.5（1熱/2冷啟動(dòng)）作為熱/冷態(tài)比。
?編程啟動(dòng)抑制“開(kāi)”可在62.5%（50×1.25）熱容量可用時(shí)盡快重啟。
?在2次冷啟動(dòng)或1次熱啟動(dòng)后，將使用接近100%的熱容量。使用的熱容量呈指數(shù)衰減
（計(jì)算見(jiàn)369手冊(cè)電機(jī)冷卻部分）。1次后僅使用37%的熱容量常數(shù)，這意味著有足夠的熱容量可用于另一次啟動(dòng)。計(jì)劃60分鐘（5小時(shí)）作為停止冷卻時(shí)間常數(shù)。因此，在2次冷啟動(dòng)或1次熱啟動(dòng)后，停止的電機(jī)將被阻止啟動(dòng)5次小時(shí)。
由于電機(jī)運(yùn)行時(shí)轉(zhuǎn)子冷卻更快，因此運(yùn)行冷卻時(shí)間常數(shù)的合理設(shè)置可能為一半停止冷卻時(shí)間常數(shù)或150分鐘。使用的熱容量計(jì)算過(guò)載元件使用熱容量算法來(lái)確定過(guò)載跳閘條件。過(guò)載程度電流決定熱存儲(chǔ)器的填充速度，即如果電流剛好超過(guò)FLC×O/L傳感器，則熱容量緩慢增加；如果電流遠(yuǎn)遠(yuǎn)超過(guò)FLC拾取水平，則熱容量會(huì)迅速增加。當(dāng)使用的熱容量達(dá)到100%時(shí)，發(fā)生過(guò)載跳閘。過(guò)載電流不一定要通過(guò)過(guò)載曲線(xiàn)才能發(fā)生跳閘。如果有熱容量已經(jīng)建立，過(guò)載跳閘將更快發(fā)生。換句話(huà)說(shuō)，過(guò)載跳閘將在規(guī)定的僅當(dāng)熱容量等于零且電流以穩(wěn)定速率應(yīng)用時(shí)，曲線(xiàn)上的時(shí)間。否則熱容量從過(guò)載前的值增加，直到達(dá)到100%熱容量和過(guò)載發(fā)生跳閘。
正確選擇過(guò)載曲線(xiàn)以進(jìn)行適當(dāng)保護(hù)很重要。在某些情況下，需要計(jì)算啟動(dòng)后形成的熱容量。這樣做是為了確保369在完成一個(gè)開(kāi)始。熱容量的實(shí)際填充是過(guò)載電流曲線(xiàn)下的面積。因此，到計(jì)算啟動(dòng)后的熱容量，計(jì)算過(guò)載電流的積分。
下面是一個(gè)啟動(dòng)期間如何計(jì)算熱容量的示例：
熱容量計(jì)算：
1.畫(huà)出與加速度曲線(xiàn)和過(guò)載曲線(xiàn)相交的線(xiàn)。這如圖7-6所示：熱第7-18頁(yè)的極限曲線(xiàn)。
2.確定繪制線(xiàn)相交的時(shí)間、加速度曲線(xiàn)以及繪制線(xiàn)與所選過(guò)載曲線(xiàn)相交的時(shí)間。
3.整合已確定的值。369的啟動(dòng)抑制元件提供準(zhǔn)確可靠的啟動(dòng)保護(hù)，而不會(huì)造成不必要的鎖定時(shí)間延長(zhǎng)，導(dǎo)致生產(chǎn)停機(jī)。鎖定時(shí)間基于電機(jī)的實(shí)際性能和應(yīng)用而不是在最壞的情況下，因?yàn)槠渌麊?dòng)保護(hù)元素。
369熱容量算法用于確定啟動(dòng)抑制元件的鎖定時(shí)間。熱容量為顯示電機(jī)溫度的百分比值，該值來(lái)自過(guò)載電流（以及不平衡電流和RTD（如果啟用了各自的偏置功能）。了解Thermal最簡(jiǎn)單的方法369的建模功能是成像一個(gè)裝有熱容量的桶。一旦這個(gè)假想的鏟斗裝滿(mǎn)，就會(huì)發(fā)生過(guò)載跳閘。鏟斗由隨時(shí)間累積的過(guò)載電流量填充，并與編程的過(guò)載曲線(xiàn)進(jìn)行比較，以獲得一個(gè)百分比值。熱容量桶根據(jù)編程的當(dāng)電流低于滿(mǎn)載電流（FLC）并正常運(yùn)行時(shí)的運(yùn)行冷卻時(shí)間
EXAMPLE
Motor data sheets state that the starting sequence allowed is 2 cold or 1 hot after which you must wait 5 hours before attempting another start. ? This implies that under a normal start condition the motor is using between 34 and 50% thermal capacity. Hence, two consecutive starts are allowed, but not three (i.e. 34 × 3 > 100). ? If the hot and cold curves or a hot/cold safe stall ratio are not available program 0.5 (1 hot / 2 cold starts) in as the hot/ cold ratio. ? Programming Start Inhibit ‘On’ makes a restart possible as soon as 62.5% (50 × 1.25) thermal capacity is available. ? After 2 cold or 1 hot start, close to 100% thermal capacity will be used. Thermal capacity used decays exponentially (see 369 manual section on motor cooling for calculation). There will be only 37% thermal capacity used after 1 time constant which means there is enough thermal capacity available for another start. Program 60 minutes (5 hours) as the stopped cool time constant. Thus after 2 cold or 1 hot start, a stopped motor will be blocked from starting for 5 hours. Since the rotor cools faster when the motor is running, a reasonable setting for the running cool time constant might be half the stopped cool time constant or 150 minutes.
THERMAL CAPACITY USED CALCULATION
The overload element uses a Thermal Capacity algorithm to determine an overload trip condition. The extent of overload current determines how fast the Thermal Memory is filled, i.e. if the current is just over FLC × O/L Pickup, Thermal Capacity slowly increases; versus if the current far exceeds the FLC pickup level, the Thermal Capacity rapidly increases. An overload trip occurs when the Thermal Capacity Used reaches 100%. The overload current does not necessarily have to pass the overload curve for a trip to take place. If there is Thermal Capacity already built up, the overload trip will occur much faster. In other words, the overload trip will occur at the specified time on the curve only when the Thermal Capacity is equal to zero and the current is applied at a stable rate. Otherwise, the Thermal Capacity increases from the value prior to overload, until a 100% Thermal Capacity is reached and an overload trip occurs. It is important to chose the overload curve correctly for proper protection. In some cases it is necessary to calculate the amount of Thermal Capacity developed after a start. This is done to ensure that the 369 does not trip the motor prior to the completion of a start. The actual filling of the Thermal Capacity is the area under the overload current curve. Therefore, to calculate the amount of Thermal Capacity after a start, the integral of the overload current most be calculated. Below is an example of how to calculate the Thermal Capacity during a start: Thermal Capacity Calculation: 1. Draw lines intersecting the acceleration curve and the overload curve. This is illustrated in Figure 7–6: THERMAL LIMIT CURVES on page 7–18. 2. Determine the time at which the drawn line intersect, the acceleration curve and the time at which the drawn line intersects the chosen overload curve. 3. Integrate the values that have been determined
The Start Inhibit element of the 369 provides an accurate and reliable start protection without unnecessary prolonged lockout times causing production down time. The lockout time is based on the actual performance and application of the motor and not on the worst case scenario, as other start protection elements. The 369 Thermal Capacity algorithm is used to establish the lockout time of the Start Inhibit element. Thermal Capacity is a percentage value that gives an indication of how hot the motor is and is derived from the overload currents (as well as Unbalance currents and RTDs if the respective biasing functions are enabled). The easiest way to understand the Thermal Modeling function of the 369 is to image a bucket that holds Thermal Capacity. Once this imaginary bucket is full, an overload trip occurs. The bucket is filled by the amount of overload current integrated over time and is compared to the programmed overload curve to obtain a percentage value. The thermal capacity bucket is emptied based on the programmed running cool time when the current has fallen below the Full Load Current (FLC) and is running normally
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