Three ways to choose a motor start capacitor

Update:29-09-2020
Summary:

Electricians, it is common to replace the starting capa […]

Electricians, it is common to replace the starting capacitor of a motor, and some are very easy. Which model is broken, and which model is replaced, generally based on the principle of replacing the original number, but sometimes there are some special cases, such as the motor starting The capacitor is seriously burnt and deformed, and the model parameters marked above cannot be seen at all. Or we don’t have the same model around, do we quickly know the parameters of the capacitor model to be changed? Here are three methods, you can choose one according to your hobbies!


One: Method rote memorization method, here is a sort, according to the power of the motor from small to large, 40-60 watt motors are generally equipped with 1-1.5uf capacitors, and 70 watt motors are generally equipped with 2uf capacitors. 180 watt motors use 6uf capacitors, 350 watts to 2.2 kilowatts of motors use 450V200μf non-polar capacitors, do not count, because the operating current has an allowable range, it is not difficult to remember these, you can quickly know the starting capacitor to replace model. It should be emphasized here that the starting capacitor and the working capacitor are worth noting, because the starting capacitor actually requires a larger current than the working capacitor, but because the capacitor selection can allow a certain floating range, most of the working capacitors are slightly larger. One point, one is used for dual purposes. This is why some electric fans have been used for a long time, the loss of capacitance has become smaller, and the fans will not start when they start, so you can replace them with a larger capacity capacitor.


Two: The theory is strong and the accuracy is slightly higher, but there are also some factors that are estimated components, so the results are not very accurate. The drawback is that sometimes it will be a little troublesome, but if you are familiar with the calculation several times, you can master this method. Just like a calculation problem, it is not as complicated as imagined. Bring various parameters into the formula. The circled result is the capacity of the optional capacitor. Calculate the optional according to the formula: C=350000*I/2p*f *u*cos∮ Among them: co∮ represents the power factor of the motor, generally 0.55--0.75, p represents the number of pole pairs of the motor, which can be calculated on the motor nameplate or can be calculated according to the formula, u represents the power supply voltage, refers to the rated state, f Represents the power frequency, our country is 50 Hz, l is the rated current, c is the capacitance


Three: A quick and accurate method is to download an electrician calculation software in the mobile phone, and fill in the parameters to be calculated. The software will automatically calculate the capacity of the optional capacitor, which benefits from high technology.


This is also a summary of experience. If the estimated or calculated capacitor cannot be bought or is not available at hand, we can choose a model with a similar capacity nearby, and try to be larger, but no matter which method is used, it must be tested after replacement. Whether the current meets the requirements, the result has been this test as a standard to determine whether the selected capacitor is suitable. If the current disparity is too large, it means that the matching type is incorrect and must be re-selected. Otherwise, it will leave future troubles and cause more trouble. As long as there are many detection steps, even if the wrong selection is made, there is a chance to make up. Therefore, this step is the key to replacing the starting capacitor.

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