Designing AC Drive Panel: Basics

VFD/Inverter panel  essentials


In this post I shall enumerate the basic requirement, design aspects, electrical aspects of vfd panel

we all know that now a days with the extensive developments in the field of power electronics
now vfd application to induction motor is now a common practice. Now in the market application specific drives are available with sophisticated control features.

Now whatever the drive make is , there is some general standards to be followed for
selecting the right switch gear
selection of filters, reactors and smoothening circuits
cable sizing
cooling clearance
arrangement of modules
panel cutout
glanding
control wiring etc
We can supply the panel with the way we want. But its not the right method. One who designing the entire system should have a good knowledge
motor load type/ Application
Ambient conditions where the motor and panel will be fixed
Total distance of power cabling
The way the cable to be routed
The IP standard to be followed

While executing the project the concerned engineer must understand client's exact requirement and should prepare the drawings and layout based on that.
Now even though the drive has got inherent ability to respond to faulty conditions, its always recommendable to go for protective power components. The most common include

sdf/mccb at incomer : mainly meant for supply isolation

HRC fuse
Thyristor fuse
Line reactors, Line LC Filters
Output reactor : if requred
Braking components : if required
Power cable selection


Line reactor selection

The equation for the reactance of an inductor is
XL = 2¶FL. Where XL is inductive reactance in Ohms, F is the applied frequency of the AC source and L is
the inductance value of the reactor. As you can see, the reactance and therefor the impedance of the
reactor is higher with a higher inductance value. Also, a given inductance value will have a higher
impedance at higher frequencies. Thus we can say that in addition to limiting the rate of rise in current, a
reactor adds impedance to an AC circuit proportional to both its inductance value and the applied
frequency


Now while selecting the filter components you should be always careful because wrong selection will result in adverse results, but from my past experiece what I understand is that if you once got the concept, if you know the electrical aspects then you can go ahead.

since the inductance is in series in the power circuit  ofcourse a small percentage of the applied voltage would drop across. 
the drive manufactures in their product catalogue mostly mentioned the specification of the suitable line reactor.
once you got the specification you can check for other make too.

This topic is not over, shall update further in coming days
those who read, if find that the post is informative please provide your valuable feed back. this would certainly help me in improving over the upcoming posts