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Precautions for the use of frequency sensitive rheostat

source:网络 date:2020-03-26 12:18:11 author:正阳兴电子
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The motor system driven by frequency sensitive rheostat has been used more and more because of its advantages such as obvious energy saving effect, convenient adjustment, simple maintenance and networking. However, the interference brought by the special working mode of frequency converter can not be ignored more and more.

The frequency converter interference mainly includes:

First, the frequency converter is commonly used in the use of thyristor or rectifier diode and other non-linear rectifier devices, the harmonic generated by the harmonic will produce conductive interference to the power grid, causing the power grid voltage distortion (voltage distortion rate is expressed by THDV, the frequency converter caused by harmonic THDV is about 10-40%), affecting the power supply quality of the power grid;

Second, the output part of the frequency converter is generally used IGBT and other switching devices, in the output of energy will produce strong electromagnetic radiation interference in the output line, affecting the normal work of the surrounding electrical appliances.

Frequency sensitive rheostat detail parameters:

The principle: change the resistance by changing the length of the resistance line connected to the circuit.

Function: adjust the frequency sensitive rheostat can gradually change the resistance connected to the circuit, so as to gradually change the current in the circuit and part of the voltage at both ends of the circuit, sometimes also play a role in protecting the circuit.

(3) Structure: frequency sensitive rheostat is composed of porcelain cylinder, coil, metal bar, slide vane and other components. The coil on the porcelain cylinder is made of resistance wires (alloy wires with high resistivity) coated with insulating paint. One end of the coil is connected with terminal post A and the other end is connected with terminal post B. The metal rods above the cylinder are mounted on the insulating porcelain frame. The ends of the rods are connected with terminal posts C and D. The metal slider sheathed on the metal bar slides on the rod and is in close contact with the coil. Where the coil can contact the slider, the insulating paint has been scraped off.

(4) connection method: whether there are several terminal posts of frequency sensitive rheostat, in the connection circuit, you can use the "up and down" connection method. "One up" means the connection of any terminal post at either end of the upper metal bar into the circuit, and "one down" means the connection of any terminal post at either end of the lower coil into the circuit.

⑸ Use: The frequency sensitive rheostat has four terminals. With a rheostat, which is placed in series in a circuit, the current in the circuit and the voltage at either end of the circuit can be changed by changing the resistance. There are six possible connections for connecting four terminal rheostats in series.

Precautions for the use of frequency sensitive rheostat

Problems to be noted in the use of frequency sensitive rheostat:

The frequency sensitive rheostat should be in series with the controlled circuit.

The frequency sensitive rheostat is connected to the two terminal posts of the circuit: "one up and one down".

(3) in order to protect the circuit, before the power should be placed away from the slide "a" position.

(4) the current through the frequency sensitive rheostat can not exceed its allowed through the large current.