Volt free contacts
Volt free contacts
(OP)
Could any one explain what is a volt free contact and how it works
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Volt free contacts
RE: Volt free contacts
Where as PLC's (unless specified otherwise) would have outputs which can have +/-24V to 48V ac/dc signal on them. They are not volt-free. Then you have to have a interveinig relay drive by PLC to get volt-free contacts.
RE: Volt free contacts
Many thanks for your post.When these volts 'free contacts"
are configured to communicate with a PLC or simply put in a motor control circuit, a control voltage(could be anything between 24V to 230V) is applied across them .Does it mean they are still volts free and no current flows through them?I would appreciate if you could enlighten me on this.
RE: Volt free contacts
RE: Volt free contacts
uses include telemetry and interlocking with other systems
RE: Volt free contacts
In olden days "changeover" contact is used for interlocking purposes as the control scheme was simpler and operates in 'OR' scheme.
With larger systems and the sequencing & interlocking are to be taken to various levels & various voltages, "voltage free" contacts have become essential. These contacs will not have the influence of either coil voltage or the power voltage of the Contactor/ relay.
These "Voltage free" contacts are used in some other circuit and some other voltage for sequencing and interlocking.
RE: Volt free contacts
The volt-free contacts do not remain volt-free 'after' the voltage (of the circuit it is controlling)is applied.
In otherwords, you can use them as you described in your second post. Volt-free does not mean they have to remain so when used in a circuit. Only that they have no voltage related to the logic or relay that is driving (actuating) them. The volt-free contacts are rated to be used on certain voltage and to carry certain current and should be used within their rating.
Hope this helps.
RE: Volt free contacts
Visit
http://www.a-tcontrols.com/pdf/MM/301-302-mm.PDF
for: volt free contact example at limit switch