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Relationship between melting rate and productivity of induction melting furnace
It should be noted that the induction melting furnace melting capacity data provided by the general induction melting furnace manufacturer on the sample or specification is the melting rate. Induction melting furnace melting rate characteristic induction melting furnaceitself, it induction melting furnace of the type of power supply and the size, and production operations irrespective system. The induction melting furnace productivity is related to the melting rate performance in addition to induction melting furnace itself, but also related to the melting operation system. Usually, there is a certain no-load assist time in the melting operation cycle, such as: feeding, slag, sampling test and waiting for test results (related to testing methods), waiting for pouring. The presence of these no-load assist times reduces the power input to the power supply, i.e., reduces the melting capacity of the induction melting furnace .
For the sake of clarity of the description, we introduce the concept of induction melting furnace power utilization factor K1 and operating power utilization factor K2 .
The induction melting furnace power utilization factor K1 is the ratio of the power output to its rated power throughout the melting cycle, which is related to the type of power supply. The K1 value of the medium frequency induction induction melting furnace equipped with a thyristor (SCR) full-bridge parallel inverter solid-state power supply is usually around 0.8 . After the Xi'an Institute of Mechanical and Electrical Engineering added inverter control to this type of power supply (usually this type of power supply only Rectification control), the value can be close to about 0.9 . Shared medium frequency induction melting furnace power supply of solid configuration (IGBT) or (SCR) connected in series half-bridge inverter K1 values of 1.0 theoretically attainable.
The working power utilization factor K2 is related to factors such as the process design and management level of the melting plant and the configuration scheme of the induction melting furnace power supply. The value is equal to the ratio of the actual output power of the power supply to the rated output power over the entire operating cycle. Typically, the size of the power utilization factor K2 is between 0.7 and 0.85 in the selected auxiliary working dead time of induction melting furnace (e.g.: feeding, sampling, testing wait, wait, etc. casting), the shorter, the greater the value of K2. The K2 value of the scheme 4 of Table 4 (dual power supply with two furnace system) can theoretically reach 1.0, and in fact, the induction melting furnace can achieve 0.9 or more when the no-load auxiliary operation time is very low .
Thus, the productivity N of the induction melting furnace can be calculated from the following formula:
N = P · K1 · K2 / p (t/h) ..................................................................... (1)
In the formula:
P - - induction melting furnace rated power (kW)
Kl - - induction melting furnace power efficiency, typically in the range of 0.8 to 0.95
K2 – - operating power utilization factor , 0.7 ~ 0.85
p –– - Induction melting furnace melting unit consumption (kWh/t)
For example, a 10t medium frequency induction induction melting furnace equipped with a 2500 kW thyristor (SCR) full-bridge parallel inverter solid-state power supply produced by an electromechanical research institute has a melting unit consumption p of 520 kWh/t , and aninduction melting furnace. The power utilization factor K1 can reach 0.9 , and the operating power utilization factor K2 can be taken as 0.85 . The productivity of the induction melting furnace is thus:
N = P · K1 · K2 / p = 2500 · 0.9 · 0.85 / 520 = 3.68 (t/h)
It should be pointed out that some users confuse the meaning of melting rate and productivity, and regard them as the same meaning. They do not consider the induction melting furnace power utilization factor K1 and the operating power utilization coefficient K2 . The calculation result will be N = 2500 / 520 = 4.8. (t/h) . It is impossible to achieve design productivity by the induction melting furnace thus selected .
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