Industrial motor drive power and control circuit supplies?
Industrial motor drive power and control circuit supplies?
(OP)
I'm trying to design a 3 phase ac ind. motor driver. I planned to obtain dc bus voltage from 380VAc to feed the motor via power semiconductors and obtain the power needed for control circuits from 220VAC via a dc-dc converter. For this purpose, 3 phase and 1 neutral line have to be connected to the drive. But i have some hesitations and questions since i have not got much experience with the commercial drives:
1- What strategy commercial drives usually follow? Seperate input for control circuits? e.g. 24VDC. or obtain from dc bus voltage which is high (500VDC or more) and makes difficult to obtain dc voltage for control circuits than obtaining from 220VAC.
2- Should i care anything while obtaining DC Bus voltage from 380VAC. When we rectify it we get max ~537V. But capacitors aren't more than 450V. Must i use serial connected capacitors? If so,then capacitance will decrease, will it suffice?
Also at a 10KHZ carrier frequency with igbts have reverse connected diodes, should i use snubber circuits on power devices with the motors lower than 15HP.
1- What strategy commercial drives usually follow? Seperate input for control circuits? e.g. 24VDC. or obtain from dc bus voltage which is high (500VDC or more) and makes difficult to obtain dc voltage for control circuits than obtaining from 220VAC.
2- Should i care anything while obtaining DC Bus voltage from 380VAC. When we rectify it we get max ~537V. But capacitors aren't more than 450V. Must i use serial connected capacitors? If so,then capacitance will decrease, will it suffice?
Also at a 10KHZ carrier frequency with igbts have reverse connected diodes, should i use snubber circuits on power devices with the motors lower than 15HP.





RE: Industrial motor drive power and control circuit supplies?
But you should know that competition is fierce and that very competent drives can be bought for less than what you would pay for the components. These drives are the result of many years of experience, optimization and "productification".
And, yes. Do, by all means, derive auxiliary power from the DC link. You will not be able to brake to stillstand on power outage if you connect the power supply to AC. For obvious reasons.
Good luck, anyhow.
RE: Industrial motor drive power and control circuit supplies?
RE: Industrial motor drive power and control circuit supplies?
That said, I agree with Skogsgurra as to making sure you really want to embark on this journey. The largest corporate giants in the world have invested mightliy in brining costs down to levels that allow no reasonable margin for new innovators, unless you bring something that has NEVER been done before and can convince a large enough market that they can't live without it. In that endeavor, using an Engineering Tips group like this to solve your problems is probably not going to serve you well, and indicates that you may be biting off more than you can chew.
I'm not trying to be negative, I'm just offering unsolicited advice based upon 1 paragraph I have seen you write, so take that for what it is worth and good luck.
"Venditori de oleum-vipera non vigere excordis populi"
RE: Industrial motor drive power and control circuit supplies?
RE: Industrial motor drive power and control circuit supplies?
So I could recommend such an activity to anyone that feels that she/he needs a deep understanding of one of the more complex and varied electronic systems that exist today. But, there is an even better way: attend classes in basic electricity and electronics. That will eventually put you in a position where you will be able to resolve issues like the one with capacitor voltage and capacity (in your OP) with great confidence.
Learning by trial and error is a painful proposition when it comes to power electronics - and dangerous as well. Exploding electroltyitic capacitors have killed one guy that I once knew. An I can thank my eye-glasses for not being blind when an IGBT module exloded right into my face. Epoxy shrapnels are not to laugh at.
So, I think that you should consider the (class) alternative. It will give you a good education and also proof that you have the skills needed. Then get a job with a good company and work your way up. There are very few short-cuts. And they seldom work.
Gunnar Englund
RE: Industrial motor drive power and control circuit supplies?
The drive will also have to withstand higher voltages (say 1000 VDC due to regeneration when inertial loads are decelerated. 450VDC capacitors are used in series with parallel balancing resistors. 450 V capacitors have higher surge ratings (550 VDC?).
RE: Industrial motor drive power and control circuit supplies?
RE: Industrial motor drive power and control circuit supplies?
----------------------------------
If we learn from our mistakes,
I'm getting a great education!
RE: Industrial motor drive power and control circuit supplies?
As my professor was fond of saying, "In logic you can make
all the mistakes you want, in power you can't make any".
This site has a huge amount of data on "how to" AC drives.
http:/
RE: Industrial motor drive power and control circuit supplies?
1. Diodes with a peak reverse voltage of at least 2,000 volts.
2. A switched or unswitched load ( bleeder resistor or dynamic braking resistor ) that will get rid of excess voltage even when the motor is not running. This is how electronic fluorescent ballasts burn out when the bulbs fail or are removed.
3. Resistance-capacitance snubbers across each diode. If you do not have these then dV/dT when a diode turns off can cause the diode to fail to turn off.
Please see http://home dot earthlink dot net/~mc5w/badnewsballasts.txt for more details.
4. Choke input power supply otherwise you will have more power quality problems and very high peak current in the diodes.
5. A 3-phase inductance or Universal Harmonic Filter in the 3-phase supply circuit. Mirus International makes a Unversal Harmonic Filter for VFDs including 1 that does single phase to 3-phase conversion. Both devices produce current waveform distortion equivalent to an 18-pulse rectifier.
Actually, you can learn just as much by taking apart old drives, especially the ones that use a combination of analog and digital circuits such as Emerson's Prism drives.
During the summer of 1994 I had to adjust/recalibrate 5 Prism drives to get 5 steel coil straighteners to work right. Once I got them to give me 60 Hertz at 6 volts DC signal input I programmed the sonar control to produce a minimum signal of 1.5 volts when calling for the motor to run so that the motor would not stall out. The motors were dependent on a shaft driven fan for cooling. Essentially, the sonar senses the depth of the steel coil loop between the straightener and the punch press. The Coiltek sonars from the Carey Corporation were programmed to operate in start-stop mode when steel demand was low and operated the VFDs as 15 Hertz soft start at low demand. At higher demands the sonar could operate the motor at up to 90 Hertz.
One problem was that somebody else had tinkered with the Prism drives thinking that they could improve performance by maladjusting the things. Prism drives are a bit of a pain to adjust and calibrate to work a dertain way but you will learn more because the only "black box" is the PROM that is used to create a sinusoidal reference waveform using a digital to analog converter.
I have also had to adjust and recalibrate an emerson Spectrum drive which is a 4 quadrant 3-phase in DC out drive. It can take a day and a half to zero offset the differential amplifiers. This is because the 10 turn pots only have 1/4 of a useful turn because they are connected +15 volts to -15 volts instead of + and - 1.5 volts. If you have time you could unsolder the 10 turn pots and install some fixed resistors to the ends to make them more useful. However, the Spectrum driveis very easy to understand because there are no black boxes.
RE: Industrial motor drive power and control circuit supplies?
RE: Industrial motor drive power and control circuit supplies?
How did we get into mechanical problems? It started electric...
How silly - that's the way it normally goes.
RE: Industrial motor drive power and control circuit supplies?
Roger that!
RE: Industrial motor drive power and control circuit supplies?
"As my professor was fond of saying, "In logic you can make
all the mistakes you want, in power you can't make any"."
What a coincidence. I also thought about this several days ago. Because first in school i direct my way to logic based things which has no danger. I changed my way to power electronics later. Now i can't be sure that i am doing everything right and checking again. Because it's not funny to make a capacitor explode or a power switch get burnt also may be dangerous. So i check my connections at every step.
About the classes; I already attended classes. But classes don't give every thing in practical especially basic ones. Even it gives you the knowledge you may not perfectly understand it and may not remember when you need it. To really understand a subject you have to need that subject and work on it. For example first i thougt that i can use a 600V capacitor. Than i couldn't find it. I thought that i can connect two in serial. Then i couldn't be sure that if it has drawbacks. I know that electyrolitic capacitors have big tolerances but i didn't first think that loading may not be equal even i read several subjects similar to this before but i forgot at that moment. This is why i'm asking here; doing as possible as low mistake. You can't learn these details even the instructor tolds you about these subjects. Because he/she tolds a lot of thing, a lot of details, a lot of experiences. Simulations also don't give you this information. Because there is no voltage limit at capacitors or unbalance etc. You have to experience it by yourself. So real world application is very important in engineering, i think. One good way, as you've said is, working in a good company but i have no opportunity at this time.
The other subject. Dc-dc converter. I first did that. It's working from the utility grid which is 230VAC. I made two mistakes there. First is not a real mistake but i see that it has no application nowadays. I must design a dc-dc converter which is fed from a high voltage dc bus. The second it must have isolated outputs for gate drivers and control circuits. I forgot to seperate it. Anyway it was my first dc-dc converter. The next time i know my requirements better and i have more experience than before. So i can do a better one. I didn't lost anything. Also it has commercial side but i didn't use that side. Because i must really make a good design, and long enough test etc. But now, i'm only learning and experienced people like the ones here, in design or applications not important, can give me very valuable knowledge. So thanks to all again.
RE: Industrial motor drive power and control circuit supplies?
Do check my link above. You will need a micro to do all this, and a fast one at that. Microchip has micros designed for this application. Also they have very inexpensive development tools. You could probably get everything for a few hundred dollars, (maybe less). Since you have knowlege in logic this should work well with your education.
I salute your attitude. Just be careful.
RE: Industrial motor drive power and control circuit supplies?
RE: Industrial motor drive power and control circuit supplies?
I think that I misjudged you. I couldn't have said the "To really understand a subject you have to need that subject and work on it" part better. Keep on to your vision. It is worth a lot.
RE: Industrial motor drive power and control circuit supplies?