Repair of magnetic starters and their maintenance

01.09.2019 House, Repair
Repair of magnetic starters and their maintenance

A magnetic starter is a device designed for switching power circuits. The first thing to do before servicing or repairing a magnetic starter is to study the documentation for that starter, or how to do it in the 21st century, look on the Internet. It is also worth knowing the weak points of magnetic starters - contact groups. It is the contact groups that need careful examination. It is worth paying attention to the fasteners and the housing, which will be discussed in the article.

External inspection

Repair of the magnetic starter begins with an external inspection. External inspection involves inspection of the housing and fasteners for cracks, chips. If cracks are present on the fasteners, this affects the volume of the work, as well as if the starter falls off and its “toad” design, then there is a danger that it will turn on the power circuit. In addition, you should pay attention to the protective covers.

It is also worth inspecting the starter for contamination. If dust, oil, traces of liquid (crystal-like growths) and other aggressive elements are present in large quantities on the case, then it is worth revising the method of protecting the starter from the aggressive effects of the external environment. Increase the degree of dust and moisture resistance. If this is not done, then the coil in the starter, which will be described later, will quickly become damp and malfunction, and the metal parts will become corroded.

Contact groups

Contact groups

Mainly maintenance and repair of magnetic starters comes down to contact groups. To inspect them, you need to open the protective cover, the first thing we pay attention to is contact groups. If there is a slight soot, then you need to clean it with a fine grain skin. As can be seen in the photo, there is no oxidation. This means that the chosen method of protecting the starter from aggressive environmental factors is selected correctly.

If traces of oxide, darkening, rust are visible on metal parts, then in this case, you need to clearly review the method of mounting the starter. More precisely, install it in a more dust-waterproof shell. Then we examine the contact groups for the presence of soot, deposits, shells. Depending on the degree of damage to contact groups, a decision is made to repair or replace.

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Example of faulty movable contacts to be replaced

The photo above shows the “surviving” contact after a short circuit. The other two are out of order and need to be replaced.

Repairing contactors and magnetic starters often comes down to repairing contact groups. This is accomplished by cleaning the soot from the contact pad. If during inspection shells, deposits are found, then these places need to be leveled with a flat small file or file. This is done in the same plane as the contact pad of the fixed contact. To ensure the best effect, you can polish both pads on moving and stationary elements.

It is highly recommended not to do all these operations with sandpaper or sandpaper, since in this case it is very difficult to maintain the plane. An unstable plane means a reduction in contact area, which in turn causes excessive heating and premature failure of the magnetic starter. It’s worth inspecting both primary and secondary contact groups.

Anchor and electromagnet

Photo magnetic core

The armature and magnetic circuit of the magnetic starter rarely suffers, but sometimes it happens that the package into which it is collected sheets of cold rolled anisotropic electrical steel crumbles. This is usually caused by factory defects. But this happens very rarely.

The most common damage that occurs when repairing a magnetic starter at the armature and magnetic circuit is corrosion. Switching is carried out by moving the armature down under the action of an electromagnet and up under the action of springs. As a result of the vibration created, the rust exfoliates and can accumulate in moving parts, which can jam over time.

Springs, mounting bolts and screws

Bolts and springs

Springs and bolts should be inspected for corrosion. Springs lose their properties over time, which means they must be replaced. A poor spring causes a slow breaking of the load, which means that the arc that occurs during the disconnection process will affect the contact groups for longer, which will accelerate their wear. It is also impossible to set an excessively strong spring.

This will lead to an incomplete closure of the magnetic flux, which will cause additional heating of the coil, and this in turn will disable it. Bolts and screws with signs of severe corrosion must be replaced. It is also worth inspecting threaded connections. Laced, corroded or mechanically screwed threads must not be used; such bolts must also be replaced.

Magnetic starter coil

When pulled out the coil of the magnetic starter from its place, the first step is to inspect its section (the frame on which the copper wire is wound) for cracks and chips. In our case, the copper wire is flooded with plastic. If there is damage, the starter will make a lot of noise during operation. Then you need to pay attention to the coil itself. On paper / plastic there should be no traces of heating (blackening), and there should be no burning smell. Typically, the main data is indicated on the coils on the side.

Basic data

This is the number of turns, operating voltage, type of current (if alternating, then frequency). The brand and thickness of the wire and the brand of the starter for which it is intended are also indicated. It is quite difficult to determine the presence of inter-turn closure. For example, abnormally low or high resistance. If the coil looks the same as in the photo above, then it can be rewound. If it is filled with plastic, it must be replaced.

Conclusion

In conclusion, we can say that after repairing the magnetic starter, you should try to manually push the anchor. If biting or slow spring rejection is observed, the starter should be reassembled or the spring replaced. Typically, magnetic starters are serviced and repaired according to a plan that was drawn up in advance depending on the number of on and off times per hour. But it is worth noting that the starter should be inspected unscheduled if the equipment that is connected through it is out of order. Typically, short circuits also affect contact groups. And sometimes equipment is damaged due to damaged contacts.

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