Re: "54Vac Three Phase" means what?
From: Rich Grise (null_at_example.net)
Date: 07/13/04
- Next message: Rich Grise: "Re: 3.3V from 36V-48V?"
- Previous message: Larty: "Stepper motor dead zone and microstepping"
- In reply to: Scrim: "Re: "54Vac Three Phase" means what?"
- Next in thread: Scrim: "Re: "54Vac Three Phase" means what?"
- Reply: Scrim: "Re: "54Vac Three Phase" means what?"
- Messages sorted by: [ date ] [ thread ]
Date: Tue, 13 Jul 2004 10:48:33 GMT
on Monday 12 July 2004 08:58 am, Scrim wrote:
> "Rich Grise" <null@example.net> wrote in message
>> It sounds like you're trying to design a power supply for the thing.
>> Would that be an accurate guess?
...
> My original plan was to use
> the 3 phase variable frequency digital sine wave generator I've designed
> (with help from this group - see thread: Digital Sine Wave Generation) to
> drive three audio ic power amps. Unfortunately I now realise that the
> required 3 phase 54Vac means I'll need an 88Voutput swing, which is beyond
> the IC's I've been able to track down.
...
> The alternative idea I've been considering is to use some logic to
> produce 3 square wave signals which overlap in the required 120 degrees (3
> phase) fashion. I'd connect these to something like the HIP4086 3-Phase
> Bridge Driver and 6 FETS.
...
This sounds good to me - Plus, isn't the RMS of a square wave equal to the
peak value?
> The HIP4086 can't quite cope with the required 88V either, but I should be
> able to find something given the amount of mains powered switch mode stuff
> around these days. I'm concerned that this approximation to a sine wave
> might be just too poor, especially given that it seems that the limiting
> factor with turbo pumps is power dissipation in the motor windings.
I souldn't worry about this at all - You might need antiparallel diodes,
but I'd think a motor's inductance would make a dandy low-pass filter. ;-)
> However, I don't need the pump to run up to speed in just 60 seconds (like
> I understand it would with the recommended supply), and think I might get
> away with a fixed frequency 1250Hz 3 phase square wave supply - who knows,
> but I don't want to invest too much effort in this, given that the pump
> may turn out to be beyond use anyway.
I don't really get what you're saying here - do you mean that they used to
ramp up the drive freq, or that it takes that long to spin up even with
just the constant power supply? In either case, I'd try to duplicate the
"real" operation as closely as I could.
-- Good Luck! Rich
- Next message: Rich Grise: "Re: 3.3V from 36V-48V?"
- Previous message: Larty: "Stepper motor dead zone and microstepping"
- In reply to: Scrim: "Re: "54Vac Three Phase" means what?"
- Next in thread: Scrim: "Re: "54Vac Three Phase" means what?"
- Reply: Scrim: "Re: "54Vac Three Phase" means what?"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
