Line reactor for VFD
Line reactor for VFD
(OP)
Hello Everybody
I have 5 HP 1730 RPM, 5.1amps, 600 Volts motor for an airlock which I want to connect to VFD. I have 9 KVA 1336 A.B. VFD in stock. My question is that do I need to connect line reactor? If yes, then what should be its rating? Also it would be good to know for future how to calculate these ratings (amps and henry).
I have 5 HP 1730 RPM, 5.1amps, 600 Volts motor for an airlock which I want to connect to VFD. I have 9 KVA 1336 A.B. VFD in stock. My question is that do I need to connect line reactor? If yes, then what should be its rating? Also it would be good to know for future how to calculate these ratings (amps and henry).





RE: Line reactor for VFD
RE: Line reactor for VFD
RE: Line reactor for VFD
RE: Line reactor for VFD
RE: Line reactor for VFD
You never want to use a reactor when it is not needed because reactors drop voltage and can cause low voltage problems.
RE: Line reactor for VFD
RE: Line reactor for VFD
I assume your reference to a line reactor is between the VFD and AC supply. In which case ensure the line reactor is sized to the VFD rating rather than the motor rating.
RE: Line reactor for VFD
The line side reactor would help protect the drive from harmful power conditions. It would also cut down on the harmonics introduced onto your power system by your drive.
The load side reactor is a cheap way to help protect the motor windings from the spikes caused by the long distance of the motor cabling.
Also, with that distance of motor leads, I would recommend a shielded cable. LAPP/Olflex makes a nice cable for the job. I believe it is called Olflex VFD Slim Cable.
Sizing the Reactor to the load is important. Line reactors do not perform as well underloaded. However, you don't want to go over the ratings of the reactor either
Here is the link to the MTE selection chart:
www.mtecorp.com/line_select.html
MTE has a lot of useful information on their website.
RE: Line reactor for VFD
When you ask about line reactor I assume you mean between the line and the VFD because that is the line side, hence line reactor.
If you were asking about a reactor for between the VFD and the load I would expect you to ask about a load reactor or motor reactor, being that side of the VFD.
But that's just me I guess.
RE: Line reactor for VFD
That may be enough to reduce the harmonic current to the point that the VFD input current is equal to the 5.1 amp output current, but it isn't going to reduce it to the 4 amp reactor rating.
RE: Line reactor for VFD
Whether a reactor is installed in front of the drive is a separate issue entirely having to do with supply power network harmonics. Do not use a reactor if the input network harmonics are at an acceptable level.
RE: Line reactor for VFD
Be sure to spec inverter duty motors (I think mine were spec'd for insulation to withstand 1600v in 2 microseconds / standard is less) [it's been awhile and my specs are at work]...
I haven't used shielded cable - cable lengths were typically less than 300ft and little opportunity for interference to parallel cabling...
Used load filters on small hp (1/2hp or less if cabling exceeded 100ft) or for larger hp if cabling exceeded 700 to 1000' -- voltage spikes would exceed the insulation withstand ratings and the load reactors kept this within the ratings...
work with your motor/VFD suppliers to make sure all components are compatible for the application...
RE: Line reactor for VFD
http://www.transcoil.com/
we use the KLC for long motor leads
And there UL and CUL listed
RE: Line reactor for VFD
I would only recommend a sinewave filter under the following applications:
True extreme lead length, greater than 3000ft. ie downhole.
HVAC where noise is an issue. The filter will transfer the noise from the motor to the filter.
Very old motors that would be difficult/costly to replace.
Shipboard where mixed and unknown loads are present.
Neil
RE: Line reactor for VFD
Nineteen years of VFD experience and doing it wrong enough times to have paid my dues allows me to say that with a good level of confidence.
On the other hand, the comment above about "always using a 5% line reactor" is not good practice either. A line reactor operating at its rated current drops the same percent voltage as its impedance % figure. So, on a 460V service running at 460V, a 5% line reactor will drop the voltage to the drive by 5% which results in 437V. Since drives cannot generally make voltage, that's all the motor is going to get at full speed. Now, just add another 5% motor lead reactor "just to be sure" and there goes another 5% of the voltage at full load. Clearly, not a good idea!
Line reactors are good things when you need them but to use them indiscriminately is a waste of money and can make other problems.
Better to use them when needed and that's all.
RE: Line reactor for VFD
As a standard on any VFD driven motor at voltages >500Vac you will need a minimum of dv/dt filters. 700ft is certainly needing sinewave filter on a standard VFD when you are looking at P-P voltages on the PWM waveform of minimum 1200v, then you have a long cable length.The motor will cook if not.
Line reactors will provide some protection on slow, low energy surges but a spike of high energy and fast acting will go straight through the AC line reactor, maybe taking out the rectifier, IGBT or if you are lucky the drive will trip.
A number of VFD's have built in DC link reactors and so the harmonic performance is as good as fitting a 5% AC reactor except you do not get the voltage drop effect that DickDV mentions. Fitting an AC line reactor to a VFD that has DC link reactors does not improve the harmonic performance that much and the downside of voltage drop and lowering the efficiency of the VFD system is an important aspect.