VFDLib

VFDLib Library

The VFDLib library provides a clean interface for basic control of variable frequency drives (VFDs).

Usage

The VFDLib functionality can be integrated into any project using a data structure and a function call.

Initialization

To use the VFDLib functionality, a variable must be declared of type VFD_typ. This variable should then be initialized in the INIT routine of your program. This initialization consists of setting configuration settings and initial motion parameters. The examples in this document will assume this variable will be named ‘VFD’.

VFD.IN.CFG.Scale.MinUnits:=	0;
VFD.IN.CFG.Scale.MinRPM:=	0;
VFD.IN.CFG.Scale.MaxUnits:=	1500;
VFD.IN.CFG.Scale.MaxRPM:=	1500;

VFD.IN.PAR.Velocity:=		100;

The interface from the VFD variable to the VFD hardware is done via IO mappings. All necessary IO points are contained in the VFD.IOMap structure. These IO points are named consistently with the IO mapping entry names for the VFDs.

Cyclic Operation

To control the axis cyclically, the VFDFn_Cyclic() function must be called in the CYCLIC routine of your program, once every scan, unconditionally. This function should not be called on the same VFD variable more than once per scan.

VFDFn_Cyclic( VFD );

The VFD variable can then be used as an interface for higher level motion sequencing programs.

Reference

VFD Data Structure

The VFD structure (VFD_typ) provides the interface to higher level programs and also stores all necessary internal information. It is divided into inputs (VFD.IN), outputs (VFD.OUT), a test interface (VFD.TEST), IO points (VFD.IOMap), an encoder structure (VFD.Encoder) and internals (VFD.Internal).

Inputs

The VFD inputs are divided into commands (IN.CMD), parameters (IN.PAR), and configuration settings (IN.CFG). Commands are used to initiate operations, and parameters and configuration settings determine how the commands will be processed. The difference between parameters and configuration settings is that configuration settings are generally set only once, while parameters might be set any time a command is issued.

Commands

Power - Power the motor. If set to 1, the motor will be powered. If set to 0, the motor will be depowered.
Run - Run the motor at speed. If set to 1, the motor will run at the specified Velocity. If set to 0, the motor will stop.
Reverse - Reverse the direction of motion.
AcknowledgeError - Acknowledge any errors on the VFD.
Restart - Restart the VFD after a fault has occurred.

Parameters

Velocity - Velocity for motion. [units/time]

Configuration Settings

Scale - These settings specify the scaling between velocity units and the native VFD units, RPM. The four settings constitute a point pair used for linear scaling.

Outputs

The VFD outputs contain status information (OUT.STAT).

ActualVelocity - Current motor velocity. [units/time]
ActualVelocity_RPM - Current motor velocity. [RPM]
DriveStatus, Extended - Extended drive status information. See the ACOPOSinverter help for details.
State - Current VFD state.
Error - An error exists for the axis. Error is reset with the AcknowledgeError command.
ErrorID - Current error ID number.
ErrorString - Current error text.

Test Interface

The test interface gives you direct access to the axis commands and parameters, interrupting any commands from higher level programs. This allows for easy testing of the axis during machine commissioning or servicing. The test commands and parameters are intended for use in an Automation Studio watch window and SHOULD NOT BE SET IN PROGRAMS.

Enable - If set to 1, TEST.CMD and TEST.PAR take priority over IN.CMD and IN.PAR. If set to 0, then TEST.CMD and TEST.PAR are ignored.
CMD - Test commands. See above for a full list of commands.
PAR - Test parameters. See above for a full list of parameters.
STAT - A reduced set of status information that is always available whether test mode is enabled or not.

Encoder

The Encoder structure is divided into inputs (Encoder.IN), and outputs (Encoder.OUT)

Encoder Inputs

If an encoder is used, the encoder should be initialized in the INIT routine.

VFD.Encoder.IN.CFG.Scale.MinUnits:=		0;
VFD.Encoder.IN.CFG.Scale.MinCounts:=	0;
VFD.Encoder.IN.CFG.Scale.MaxUnits:=		1;
VFD.Encoder.IN.CFG.Scale.MaxCounts:=	1;

Counter - Encoder position input. THIS VARIABLE SHOULD NOT BE MAPPED TO IO OR SET IN PROGRAMS. It is automatically set to VFD.IOMap.IN.Counter.
CFG.Scale - These specify the scaling between velocity units and encoder counts per second. The four settings constitute a point pair for linear scaling.
CFG.tf, CFG.deadband, CFG.K - These settings configure the internal speed estimator used to report the current encoder speed. For details on these parameters, please see the documentation for the SpdEstLib library.

Encoder Outputs

SpeedUnits - Encoder speed in units/s.
SpeedCounts - Encoder speed in counts/s.
STAT.Error - Encoder scaling error exists. Error is automatically reset when the scaling error is corrected.

Error ID Numbers

3 - “CFF”: Incorrect configuration (parameters)
4 - “CFI”: Invalid configuration (parameters)
5 - “SLF”: Modbus communication interruption
6 - “ILF”: Internal communication interruption
7 - “CnF”: Communication option card
8 - “EPF”: External fault
9 - “OCF”: Overcurrent
10 - “CrF”: Capacitor pre-charge
13 - “LFF”: 4 - 20 mA loss
16 - “OHF”: Drive overheating
17 - “OLF”: Motor overload
18 - “ObF”: DC bus overvoltage
19 - “OSF”: Line supply overvoltage
20 - “OPF”: Motor phase loss
21 - “PHF”: Line phase loss
22 - “USF”: Line supply undervoltage
23 - “OCF”: Motor short-circuit (phase to phase)
24 - “SOF”: Motor overspeed
25 - “tnF”: Auto-tuning was unsuccessful
26 - “IF1”: Unknown rating
27 - “IF2”: MMI card
28 - “IF3”: MMI communication
29 - “IF4”: Industrial EEPROM
30 - “EEF”: EEPROM memory
31 - “OCF”: Impeding short-circuit
32 - “SCF”: Motor short-circuit (to ground)
33 - “OPF”: Motor phase loss - 3 phases
34 - “COF”: Communication interruption, fault line 2 (CANopen)
35 - “bLF”: Brake control
36 - “OCF”: Power module, specific to 15kW drives
55 - “SCF”: Power module or motor short-circuit, detected at power up.