DC LINK
DC LINK
(OP)
Can anyone please explain exactly what the function of the DC link in an inverter drive is?
Thanks
Thanks
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RE: DC LINK
Since this is outside my area, standby for someone else to confirm or correct.
RE: DC LINK
RE: DC LINK
AC power at fixed frequency (50 or 60 Hz) ==> rectify to DC ==> DC Link ==> invert to AC at variable frequency
Best to you,
Goober Dave
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RE: DC LINK
Thanks
RE: DC LINK
I don't think you need to be accessing the DC link to power other things. I don't know your supply voltage, but on a 480 VAC drive the DC link is in the 700 VDC range...
Best to you,
Goober Dave
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RE: DC LINK
I actually had a customer come up with the same question once. He needed around half an ampere at 24 V and thought that it would be cheap and easy to drop the 560 V DC via a resistor down to 24 V. There are three problems with that approach:
1. there will be around 250 W dissipated
2. there will not be any voltage regulation
3. there will be no insulation between grid and load
On top of that, you need very powerful fuses or brakers to protect your system in case of a short or a ground fault.
So, don't even think of that.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: DC LINK
So, in essence, an inverter hangs on the DC link. In drive systems where you have one large rectifier (controlled or uncontrolled) you can feed multiple inverters from this DC supply. This is called a common DC bus drive. In applications such as paper or steel, you can have driven loads or regenerating loads on the same bus. As long as you do the correct engineering to size it correctly. This is when the drives business gets fun.
On a traditional converter (VFD), you will have capacitors hanging onto the DC bus required to smooth out the supply and sometimes DC link reactors to provide additional smoothing and minimising harmonic distortion.
For a VFD, measuring the voltage on the DC bus is the means to understand if the unit is functioning correctly; both for rectification and also in the event of any regeneration (if on an uncontrolled rectifier). So, typically on all vfd's, you will have terminals that can be used to measure the dc voltage.
Likewise, on some but not all drives, you will have some means to dissipate regenerated typically via an additional transistor connected on the DC bus that monitors the DC bus voltage and if it reaches a level that would usually cause the drive to trip, it 'dumps' the excess into a series of resistors that can be connected onto the DC bus.
So, there are plenty of things that can be connected onto onto the DC link, as long as it is not fingers. That would hurt.
I use the term "traditional" throughout because there are many different topologies these days for a 'drive'.
RE: DC LINK
Bill
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"Why not the best?"
Jimmy Carter
RE: DC LINK
Rather than playing a game of 20 questions, why don't you state the reason for your question? It sounds as if you have an idea of something you want to try doing with the DC connections in the drive.
"Will work for (the memory of) salami"
RE: DC LINK
RE: DC LINK
Boy, the cost of a DC power supply sure seems small compared to the cost of that drive and the cost of the energy you'll expend and the other disadvantages of the voltage divider or even a DC-DC converter. See Skog's note four posts above this one, read it again. You have 480 VAC (or possibly 200 - 240 VAC) right there for power, too.
480:120 150 VA control transformer: USD$50.00
120 VAC to 24 VDC power supply 100W: USD$100.00
Avoiding a risky solution: priceless
That's an Eaton transformer and an Idec switcher. You could get the whole deal for USD$50 if you do it on the cheap.
How much current do you need at 24V?
Best to you,
Goober Dave
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RE: DC LINK
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies