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10-05-2012 09:36 AM

Choose the right inverters

What's the general factors you will consider when choosing an inverter?

We know inverter is used for controlling motor speed. It's also for motion control and energy saving.

So when you choose the frequency inverter, what's the most important factors that will affect your decision?

The performance? The brand? The service? The reliability? and other things?
10-05-2012 02:39 PM
Top #2
10-05-2012 02:39 PM
I would say that all these technical & financial matters are all important ones, but the most important is before all to clearly understand what will be the application and process where will be the inverter, note that you can have high quality drive if you use it for fan you'll lose money, efficiency, time to commission...at the opposite if you take a fan drive for roller mill application it will not work....

so 1st thing is to define clearly application and process because it will tell you what you need to control as much as possible and will give you some ideas where to go..... important values to control, torque, speed, efficiency & power on network, several single drive, one converter and several inverter, brake, regenerative, cos phi, motion application, open loop, close loop, direct torque control, V/F control, current control....to define the best frequency inverter, before define at best your need and regulation type, the ROI is only important in HVAC system, for big application like tunnel boring machine is efficiency and torque regulation, for Pipelay system is efficiency, harmonic (not acceptable on a boat) torque and speed regulation with master and several slave controls....

so clearly first application and regulation, then you'll find easily the inverter type....to finish, I would say that going with the fact that more than 75-80% of world application are pump and fan, all inverter manufacturers can manage this, so just need to check harmonic, efficiency and reliability.
10-05-2012 10:42 PM
Top #3
10-05-2012 10:42 PM
For your application, consider if you will have enough DC voltage headroom at maximum speed (peak back EMF) in order to push sufficient current necessary to sustain the machine torque. If not, please apply phase advance especially for BLDC machines.

you need to evaluate the average switching + conduction losses of the semiconductor devices under maximum torque and speed conditions (worst case) to determine the size of heat sink and thus keep the device junction temperature at acceptable level. Remember the switching loss depends mainly on frequency whilst conduction loss depends chiefly on the current through the device. You can optimize the frequency converter efficiency and lifetime this way, i.e. through proper thermal modeling.

Lastly, take protection design into account if you must operate the inverter drive safely and reliably.
10-06-2012 09:44 AM
Top #4
10-06-2012 09:44 AM
The Application should be considered first, as this tells the majority of the story which should include what the application, inverter drives and motor placement environment will be, the driven motor should also have been properly selected for the application and environment and utilized for Drive Sizing allowing adequate headroom for current and bus voltage levels to include motor lead length and input supply and output waveform filtering requirements, proper carrier frequency selection again for the application, proper cooling for both frequency inverter and Motor, adequate and proper Voltage and Current Power Source and conductors, proper grounding and grounding conductors, properly selected Output conductors considering length to motor, proper wiring layout, both control and power and correct sheilding/separation of types and voltage levels, correct control system architecture to support the application, stable and fast communications capability and selection which is necessary in the majority of systems today, also select the variable frequency inverter that can be supported and serviced in whatever part or parts of the globe the inverter will be in when the unexpected occurs, with applications engineering support as well as technical and sales support. After you look at all of this, call ABB or Siemens, they'll be happy to assist and supply your every need.
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