Friday, April 27, 2018

Sensorless Vector control; Sensorless Vector control Vs V/f control


Variable frequency drive Sensorless Control

The variable recurrence drive designs of the sensorless control contain the accompanying extra capacities, which supplement the conduct as indicated by the parameterized V/f trademark.

Slip compensation

The heap subordinate distinction between the reference speed and the genuine speed of the 3-stage engine is alluded to as the slip. This reliance can be remunerated by the present estimation in the yield periods of the variable recurrence drive.

The enactment of Operation Mode for the slip remuneration empowers as speed control without input. The stator recurrence and speed are revised relying upon the VFD stack.

The variable recurrence drive slip pay is enacted amid the guided appointing. The Stator Resistance is required to guarantee a right capacity and is estimated amid the guided authorizing.

On the off chance that no guided dispatching is executed, the slip pay can be enacted physically. In these cases, enter the VFD esteem for the Stator Resistance physically as indicated by the engine information sheet.

The variable recurrence drive control conduct of the slip pay must be streamlined through the parameters on account of particular applications. The VFD parameter Amplification decides the rectification of the speed and the impact of the slip pay relatively to the difference in stack. Parameter Max. Slip Ramp characterizes the most extreme recurrence change every second keeping in mind the end goal to stay away from an over-burden on account of a heap change.

The VFD parameter Frequency Lower Limit decides the recurrence as from which the slip remuneration winds up dynamic.

Current limit value controller
Through a heap subordinate speed control, as far as possible esteem controller guarantees that the VFD framework isn't over-burden. This is reached out by the astute current points of confinement portrayed in the past section. As far as possible esteem controller decreases the heap on the VFD, e.g. amid increasing speed, by halting the quickening incline. The turn off of the variable recurrence drive which happens when the increasing speed slopes have been set at an exorbitant inclination is in this way avoided.

 

The variable recurrence drive control conduct of as far as possible controller can be set by means of the relative part, parameter Amplification and the coordinating part, parameter Integral Time. In the event that, in uncommon cases, advancement of the controller parameters is required, continue with the accompanying advances:

               Change parameter Current Limit with a major advance, dissect the adjustments in the Scope.

               For a more unique conduct increment Amplification or potentially diminish Integral Time.

               For a less powerful conduct diminish Amplification and additionally increment Integral Time.

Behavior in motor operation:
On the off chance that the VFD current set by means of parameter Current Limit is surpassed, the initiated current point of confinement esteem controller will lessen the yield recurrence until the point when as far as possible is never again surpassed. The yield recurrence is decreased as a most extreme to the recurrence set by the parameter Frequency Limit. On the off chance that the present esteem dips under the variable recurrence drive Current Limit, the yield recurrence is raised back to the reference esteem.

Behavior in generator operation:
In the event that the VFD current set through parameter Current Limit is surpassed, the enacted current breaking point esteem controller will expand the VFD yield recurrence until the point when as far as possible is never again surpassed. The yield recurrence is expanded, as a most extreme, to the set Maximum Frequency. On the off chance that the current is underneath the variable recurrence drive Current Limit, the yield recurrence is decreased to the required reference esteem once more.

In a Scalar drive (V/Hz just), the drive releases a Voltage a Frequency as indicated by the speed you have chosen. In any case, the VFD has no clue regardless of whether that had the coveted impact on the engine and load; it does it's thing and trusts in the best. On the off chance that the heap ends up being more than the engine can deal with, the engine backs off, the slip increments and the engine pulls more present and makes more torque, yet this is a "messy" process, best case scenario. So basically the drive gives a yield, the heap makes a "blunder" in execution, yet the drive doesn't generally make a move. The final product isn't generally compelling.

In Vector control, the VFD utilizes input from the engine to see the blunder, at that point to decide the correct vector of voltage and recurrence to deliver precisely what is expected to adjust the mistake. It has a rapid processor to do the math and rapidly change the yield voltage and recurrence example to augment the torque and/or fix the speed control. Along these lines, you can work an engine at Breakdown Torque at any speed, even zero if vital.

Vector control can be proficient with outer input from encoders called Closed Loop Vector or Field arranged Control (FOC), as you are doing, or with what is called "Sensorless Vector Control" (SVC) or "Open Loop Vector Control". The two names are actually off base; there is dependably a sensor and it is constantly shut circle. Yet, the distinction is in that what is called SVC utilizes exceptionally delicate current sensors within the drive to observe precisely what is happening, and contrasting it with a scientific model it has made of the engine amid setup (the "tuning" methodology). The two techniques work fine, yet the SVC has one restriction; it can't watch the engine execution if the engine isn't moving, i.e. zero speed; like what you would need with a lift. FOC, where you have the encoder criticism, can do that.

So for you, Starting Torque will dependably be most astounding and repeatable with Vector control of any kind contrasted with Scalar control. On the off chance that you require it at Zero Speed since you are expecting to discharge a brake and you need full torque to start with, at that point you require FOC. If not, SVC will likely work fine and you won't require the encoder.