Contactors are very common component that can be found in almost any electrical circuit . Contactors being used in electrical control circuits where high current switching required . Relays do the same job but they lack handling high current loads . You can find one or more contactors in motor control circuits . Most common type of Contactor is the three phase contactor . However , There are single phase or modular type Contactors as well . The current handling capabilities are different from Contactor to Contactor . You need to select a Contactor that can handle more current than the applications maximum current load .Good long lasting Contactors can be very expensive. But , Cheaper ones are available too .But , Cheaper ones have to be repaired frequently due to low cost materials they used to manufacture the Contactors. Here in this tutorial we will discuss how to repair contactor
Why Contactors get damaged ?
There are many reasons that can cause the Contactors to go bad . However , since different manufacturers use different materials and different techniques when building Contactors ,The damage of the Contactor can be different from manufacturer to manufacturer. Here are some of them .
High current flow
If the equipment that controlled by the Contactor draws more current than the maximum rated current of the Contactor , This will damage the Contactor points . The amount of damage depends on the time that excessive current flow through the contacts and the amount of times contacts breaks and makes contact .
Rust & Oxidization
These are the two things you don’t want in any electrical circuit . Depend on the weather condition the rust and oxidization formation on the metal parts of the Contactor can vary . Place of the equipment also affects the formation of rust and oxidization . Manufactureres use different steps to prevent or limit the formation of oxidization and rust such as plating . But , These steps cant protect the components for ever .
Most factory environments are filled with dust and other small particles . If the panel box is not properly closed the dust can go inside the contractor . These dust particles can prevent proper contact between the contact points . Thus , causing damage to the contact points due to low area of the contact surface .
The coil is a main component inside the Contactor . It’s a long insulated coil that wrapped around a core . The amount of coil turns and amount of current flow through this coil decides the magnitude of the magnetic field . However , This coil’s insulation can be damaged due to heat and age . This can cause short circuit damaging the coil .
As the time pass the mechanical parts can wear out due to friction . Springs may lose their tension . Causing slow contact speed between contact points . Thus , Causing arks between contact points.Damaging the contact points .
In order to repair a electrical Contactor you must disassemble it first . For this tutorial we will discuss how to repair Schneider Electric’s LC1D32 (3Phase) Contactor .Whatever the Contactor is Examine the outer housing and figure out how to disassemble it . If you cant figure it out , search it on the internet . The below steps will explain how to disassemble the Schneider Electric’s LC1D32 Contactor .
Schneider Electric’s LC1D32 top half and bottom half is held together by simple plastic latches on the top and bottom of it. Press both at the same time while pulling the top half out .
In the bottom half you will see the coil pack , Fixed Iron core . Pull the coil pack out . Then , pull the fixed Iron core out .
Remove the top iron core by pulling the side locks to sides .
In order to access the top part you have to remove the top shell of the housing . There are two latches at each side pushed against the walls of the housing . So , In order to pull the top shell out widen the housing from sides while pushing the auxiliary lock part . The top housing will come off easily .
Cleaning the Iron Cores
When the current flows in the coil the fixed iron core will become a electromagnet .Moving iron core will attract to the fixed iron core . The iron cores will impact each others on the faces . However , If there is anything in between these faces this will prevent proper contact between contact points . That’s why you need to clean the faces of each iron core .
• If you managed to disassemble your Contactor . You have the access to the iron cores . Remove them from the housing .
• Take a sand paper , The first sand paper grid size depends on the amount of rust buildup in the faces . If there is great amount of rust , You need to select a coarse grit sand paper (80 – 120) . If there is no much rust start with fine grit sandpaper (220 – 400) .
• Lay the sandpaper against a flat surface (Sanding side on top) and put the Iorn core face against the sand paper on the top.
• Hold the sand paper using one hand while moving the iron core in a linear direction (Up- Down or side to side) . Apply some pressure to while sanding .
• Check the iron core face frequently . Sand it until the rust is gone .
• Increase the sand paper grit size . If you used coarse grit sand paper first , next use a fine grit . If you have used fine sand paper first , next use a super fine (600 – 800) grit or ultra fine grit (800 – 1000) sand paper .
• Sand it until you get a smooth surface . Do it to both iron cores .
Cleaning Fixed Main Contact Points
Remove the terminal screws that holding the contact points . Pull the contacts from the housing .Check the damage on each contact point . If there is no or less damage leave them . Take only the once that are damaged .
Lay the sand paper on a flat surface . Start with a fine sandpaper .
Put the contact against the sand paper . Hold the sand paper by one hand . Move the contact against the sanding surface in a linear direction . Make sure to only sand the contact point .
The face of the contact point should be parallel to the sanding surface . The sanding should result a flat surface on the contact point .
Check the contact point surface frequently . Once the groves are gone . Stop sanding with that sanding paper and sand the contact point surface with a super fine or ultra fine grit sand paper to finish it .
Cleaning Moving Contacts
The moving contacts may be concealed inside a the housing. You have to take apart that housing . Inside the moving contacts that held by springs . Remove the springs by compressing them and pushing them out . Once the springs are removed you can pull out the moving contacts .Check whether they are damaged or not . Select the once that are damaged and sand them as in the previous section.
Cleaning Auxiliary Contacts
When cleaning auxiliary contacts using sand papers must be only if necessary . Because , These contacts points are small and sanding them with any sand paper have less grit size than 400 can damage the contacts . Clean them carefully . Prevent any over sanding these contact points .
Any mechanical part that’s inside the contractor that have rust which can prevent any free movement need to be cleaned . However if the rust is very less you can use any rust cleaning liquid available on the market to clean them . However do not use these products on the contacts or terminals .
The wire terminals can also get rust on them . You can use sand paper on them to clean them . But , you may have to copper plate them afterwards . Because , Some of these terminals are plated .
Springs inside can also get rust (Depend on the materials they made out of). If there is rust on the springs you may have to replace them .
Repairing The Coil
When it comes to coil there can be oxidization on the coil terminals. If there so . Clean the with a brush dipped in isopropyl alcohol . Don’t use paint thinner . Because , It can damage the insulation if dropped on the coil pack .
If the coil pack is damaged . You have to re-wind the coil pack . unwrap the coil pack and measure the coil windings weight . Buy the same gauge coil at same weight . re-wind the coil pack . However , You wont be able to get the machine wingding finish . Try your best to wind it so that it can be fit inside the Contactor . If you cant wind it hire someone who have a machine to wind the coil pack . Solder the wire ends to the coil contacts .
Conclusion – How to repair a Contactor
Contactors can be expensive component to replace . The best thing about Contactors is that they can be repaired easily . Most of the time it’s the main contact points that get damaged . This is due to the sparks caused during the contacts touch each other . However , Over the time this damage can become severe and prevent the contacts being made between the contact points . Avoid sanding contact points that are good in shape . Once sanding done the contact point surface should be flat and smooth . If you wants to check whether the contact points touch each other properly place the corresponding contact points faced to face and try to see through the contact surfaces . If you cant see through , You have properly sanded the contact points . However If the damage is severe , Replace the Contactor instead of repair .