Although the contactor is probably one of the most common components in an industrial / motor control application, selecting one correctly requires detailed application information to be provided.
There are 3 key elements to a contactor
- Main contacts (also referred to as main poles)
- Auxiliary contacts
- Coil (part of the electromagnet used to energise the contactor).
Each of these elements should be fully specified based on the application;
1. Main pole selection criteria
- How many required in either normally open (N/O) or normally closed (N/C) format
- Current rating in amps.
- Voltage rating in AC or DC
- Duty (either AC1, AC3, DC1- DC5 etc). In the absence of a specific duty, a full description of the nature of the electrical load (e.g. lighting , resistive heating etc), making current, breaking current and continuous current through the contacts.
2. Auxiliary contacts selection criteria
- How many required in either normally open (N/O) or normally closed (N/C) format. Possibility of time delayed auxiliary contacts with certain product ranges.
- If not used in standard low power signalling application, details as per main poles required.
3. Coil selection criteria
- Voltage of coil (Note: The coil is often a different voltage to the main poles).
- AC or DC voltage;
- Frequency of coil if AC (Usually 50Hz or 60Hz)
- If DC coil, is low consumption required (available for certain ratings of TeSys D and TeSys K contactors).
Any additional information available should be provided, for example
- Is the contactor to be enclosed, i.e. is an enclosed motor starter required?
- Specific design requirements (e.g. Modular)
- Number of operations per hour
- latching operation
- Environmental considerations such as ambient temperature etc.
- Are any ancillary parts required such as mechanical interlocks, busbars, thermal overload relays or motor protection circuit breakers?
Released for:Schneider Electric Ireland
