5)Maintenance tips

Maintenance tips

Siemens NEMA contactors have a robust design and a rugged construction and thus do not require frequent maintenance. Nonetheless the following items can be added to your preventative maintenance program to help further ensure equipment protection and minimum unplanned down time.

1. Routine inspection: Inspection consists of observation for signs of overheating, dirt, loose parts, noise and any other signs of abnormalities. It will help to monitor the state of contactors.


2.Keeping the contactor clean will help eliminate overheating, high voltage leakage and breakdowns. Clean by blowing the dust and dirt away with a low pressure dry air stream.


3.Terminals: Tighten Terminals periodically because

a) Connections have a tendency to loosen with time – particularly those of aluminum which is soft material



b) Vibration may result in loose connections that will eventually cause problems.
Note: Brittle or discolored wire insulation may be an indication of a loose connection.



4.Contact condition: Remove the arc cover and inspect the contacts. Replace all 3 contacts if one or more of the following conditions exists:

a. Silver cadmium tips are unevenly worn,
b. Silver cadmium tips are nearly worn down to the copper material of the contact,
c. Copper material of moveable contact is discolored indicating over-heating.

Note: It is normal for the Silver cadmium tips to be discolored.
It is due to formation of silver oxide which is nothing but good conductor



5.Clean the contacts with CRC2-26. Use care not to drop magnet or scratch the pole faces of either magnet or armature.

6. Magnets In case of rust/dust accumulation on the magnet faces clean them with CRC 2-26 / Chamoi leather. Do not use degreasing agent as petrol. Dust/rust affects contactor performance and cause humming.

Do not clean magnets with share/pointed objects. Filing upsets the mating of the magnet faces. Clean lightly with fine size 00 emery papers if required.

Fig.CRC2-26


7. Corrosive atmosphere: Overheating takes place due to the formation of foreign films at the connections and on the springs. For such applications, contactors have to be suitably derated. Occasional spraying with CRC 2-26 prevents reaction of the silver parts with the atmosphere and minimizes damage.




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