How does PLC interface to variable frequency drive controller
The System of VFD which abbreviate from variable frequency drive generally consists of
an AC motor, a device controller and an operator interface.
How to communicate with variable frequency drive of PLC unit?
Most VFD have a digital, analog and communication interface, you can use to exchange with a remote control.
|
Digital signals are Start, Stop, Rotation CW, CCW Rotation, Jog, Speed Set 1
Set Speed 2 (this can drive the speed parameter), management status, alarms .
Analog signals are the reference speed, speed feedback, current, voltage, DC voltage, bus, RTD feedback .
Communication bus of the digital and analog signals via Modbus, Profibus-DP, Ethernet / IP,
ControlNet, and many others, depending on the manufacturer.
And let SNCE multiple connections, you will save a lot on the cable, one cable run many nodes PLC
We come to try to understand the VFD system before continue to read more in PLC interface with VFD.
VFD motor
|
The engine used in a VFD system is usually a three-phase asynchronous motor. Some types of one-phase motors can be used, but three-phase motors are usually preferred. Different types of synchronous motors offer advantages in some situations, but the induction motors are suitable for most purposes and are usually the cheapest option. Engines designed to operate fixed line speed of tension are often used, but a number of improvements to the standard design of the engine offers increased reliability and improved performance VFD .
VFD Controller
Variable frequency drive controllers are solid state electronic devices to power conversion.
|
The usual design first converts direct current electricity through an intermediate bridge rectifier.
Intermediate DC power is then converted into a quasi-sinusoidal AC using an inverter circuit. The bridge rectifier is usually a three-phase diode, but controlled rectifier circuits are also used. Since the power is converted to DC, the number of units will accept single phase and three-phase input power (acting as an inverter and a phase speed), but the device must be reduced by using the method of monophase as only one part of the bridge rectifier is connected to the implementation of load
This site is really a question. If it wants to integrate into the existing system, or if a stand-alone project.
The choice depends on your choice of technology. Certainly what I call the old way of hardwiring I / O is still working,
well, not really practical with new technology we have available.
Speaking from the direction of Allen Bradley (what I normally use), you can use the Ethernet / IP, ControlNet and DeviceNet.
I do not think the SERCOS VFDs, I think it’s servo-protocol. My choice is Ethernet / IP.
Since I do not know what brand you use, I’d Logix platform (PLC) and PowerFlex 4, 70, and
700 series are great. The use of Ethernet / IP (22 or 20 E-comm module) and ControlLogix is very cool.
It’s as simple as adding the card in ENBT I / O tree and add to drink. You have done.
Even the brand for you. All you have to do is logical and proper use of tags for you.
It can not much easier than that. ControlNet and DeviceNet are also quite simple,
these two are just not the choice of protocols for disk drives. We are using Ethernet / IP for years and it works great .
At minimum, you must:
1st Install relay 1 ‘pilot’ in the unit area. This is your “Run” relay. Drive relay with discrete output of your PLC.
2nd The unit is a dry contact output indicating that the “Running.” Discrete Wire to enter the PLC.
3rd If you or a reference rate of demand. The best way would be an isolated analog output 4-20 mA drive.
Of course, depending on the characteristics of station may be the number of digital interfaces available, including Allen-Bradley Remote I / O, DeviceNet, or bus.
Depending on the application, you still want analog speed reference for the digital start / stop / status.
For security, you too will want to use a type of dry-contact Emergency Stop.
