DC Drives

[leitmotif]

Actually, I like kittydog's idea best. The problem with a DC drive is that the SCR's depend on the AC input to commutate properly. With DC inputs, that's not available and the concept becomes non-functional.

With a 220VDC supply, you could use a 230V three phase input drive, connect the DC directly to two of the inputs and get 230VAC out. Now, change out the DC motor for an equivalent hp and speed 230VAC motor and the problem is solved with all standard components.
Why not!

DICK I looked into taking an off shelf VFD (3 phase input) and hooking battery direct to DC bus for the electric vehicle project. Several people tell me that like what you stated with a DC drive the VFD uses the line 60HZ as the clock (time base or referance) for triggering the IGBTs. Are they correct?

Dan Bentler

 

[DickDV]

No, Dan, the 60Hz input is not used for either of these two purposes.

We power AC drives from a DC bus whenever we do a larger sectional system which must pass motoring and regen energy around the various sections freely.

In those cases, usually we have a single DC power supply and all of the sectional AC drives powered off of the DC bus. There is no AC input at all and the drive operates normally, except without the AC input.

 

[leitmotif]

Dick
I do not want to hijack thread SO should I do rest by personal email?
The question now is
ASSUMING I have large enough battery (around 300V)
and battery voltage will not droop far enough to create VFD DC bus low volts during heavy current draw
I can get large enough VFD originally designed for 3phase 230V

Can I take off shelf VFD (say around 30 HP) and tie direct to battery on DC bus?

Which would you recommend if so?
Dan Bentler

 

[kittydog42]

I realize that 220VDC is not the same as what the DC bus would normally show with a 200VAC input, but wouldn't the drive still power up and run the motor, albeit at a reduced maximum output? Isn't the formula 1.41 times the AC in goes to the DC bus?

 

[MifPT]

Hello Guys:

Could anyone help me a recommended brand for a Variable DC Drives?
I've been searching on the internet and cannot see what i'm searching for.

I need a Variable Speed Motor Controller with a 220VDC input. As I search all DC drvies has a 100-240VAC input. What I need is a DC input Variable DC Controller for a single phase,1.5kW, 1200RPM DC motor. This motor is for Emergency Purposes that is why I need a Variable Speed Drive for this motor with a 220VDC input power.

Could anyone recommend me a leading brand?



regards,
recycled_mind

I've used ones from Sprint Electric:
http://www.sprint-electric.com/


They have worked just fine...

Miguel

 

[DickDV]

Dan Bentler, how about contacting me directly. The channel is rbdv then 01 then the ampersand symbol then gmail then dot then com. Hope that frustrates the spammers.

 

[jdbrandt]

Bonitron makes a DC supplied drive, but I don't know if it would handle 220VDC.
SSD does have a product that uses a common DC bus (890 series) but I'm
pretty sure they'd prefer to make their own DC to control their drives.

 

[Electrically_Bound]

I work in an old (over 100 years) factory that has a lot of equipment that is powered by 250VDC. We were looking to install a DC drive to replace an antiquated mess of contactors and resistor banks. The cost of running AC to the motor would have been very expensive. The motor was 150 HP. But in your application you are dealing with a rather small motor. I'm not sure if your motor's insulation could handle it, but what about designing a variable pulse width 220VDC "drive" using one or two transistors.

One thing you need to make sure about is how the 220VDC is supplied. In our factory (and I know of another one that is the same way) You have three conductors that supply the DC power: 125 VDC, -125VDC, and common. You get 250VDC by going across the +125VDC and -125VDC. If nothing else is using these two or three conductors of DC, you might want to consider rewing the DC lines for AC or placing the drive far awy from the motor and use the existing power leads as long motor leads (I'm not sure this would be legal by NEC). Just some things to think about.

 

[Electrically_Bound]

If you want to go the old fashioned route, you could put in an M-G set. Usually an M-G set (motor-generator set)consists of a three phase motor whose shaft is directly connect to that of a dc motor, but in this case you could have a dc motor driving the shaft of an ac generator. The output of the AC generator could be used to power a conventional DC drive. As archaic as this solution sounds, it is still in use on some big cranes that get there power from 250VDC rails, and they use this arrangement to provide clean AC power to the crane.