Gerrie Posted August 26, 2020 Share Posted August 26, 2020 31 minutes ago, phil.g00 said: Things have come a long way since star/delta starters I see. From what I understand a soft starter (cheaper) should halve the standing starting current surge, and a VFD (more expensive) could possibly limit it to 110% of full load. The nice thing on a VSD is you can increase the acceleration ramp time to even a few minutes and do away with high starting current. I just don’t know how a VSD will react being connected to a solar inverters supply, there might be big power factor losses that can badly influence the efficiency. I have a small 1.1KW single phase VSD that can run a three phase motor but have not yet tested it on my solar inverter supply. I don't currently have a three phase motor to test it on, but I am planning to do this experiment as soon when i get a three phase motor. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted August 26, 2020 Share Posted August 26, 2020 (edited) 39 minutes ago, Gerrie said: I don't currently have a three phase motor to test it on, but I am planning to do this experiment as soon when i get a three phase motor. There are VFD's and then there are VFD's. The first step in the VFD chain is full wave rectification and is normally done with 6 pulse diode bridge. Although at extra expense though there are VFD's that use fancy phase-shifting techniques to utilize 12, 18, 24 or 36 pulse bridges. Which considerably reduce the harmonic distortion. Top marks goes to active IGBT rectification though but at 250% cost premium apparently. Here is a nice paper for those that want to know what combos do what in terms of THD: http://www.aic-controls.com/fullpanel/uploads/files/abb-technical-guide-6-harmonics.pdf Edited August 26, 2020 by phil.g00 Gerrie and ___ 2 Quote Link to comment Share on other sites More sharing options...
___ Posted August 26, 2020 Share Posted August 26, 2020 (edited) 1 hour ago, phil.g00 said: The first step in the VFD chain is full wave rectification And to add to what you said here, the kind that runs directly from PV would of course not have this first step, since it already starts from DC. But the rest remains very similar, except that the MPPT is also in control of the output power/frequency. Hey... where is our resident DC guy anyway? Edited August 26, 2020 by plonkster Quote Link to comment Share on other sites More sharing options...
___ Posted August 26, 2020 Share Posted August 26, 2020 1 hour ago, Gerrie said: do away with high starting current There are some limits to this. There is usually a minimum starting torque, applying any less power than this heats up the motor windings without getting the thing moving, and is a very bad thing to do. So generally you'd have to program things so that it only starts up once it has enough to get things going, and then from there on it can ramp it as slow as it wants to. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted August 27, 2020 Share Posted August 27, 2020 4 hours ago, plonkster said: And to add to what you said here, the kind that runs directly from PV would of course not have this first step, since it already starts from DC. But the rest remains very similar, except that the MPPT is also in control of the output power/frequency. I think I'd forego this DC efficiency in favour of having the PV available for other things as AC. ___ 1 Quote Link to comment Share on other sites More sharing options...
___ Posted August 27, 2020 Share Posted August 27, 2020 6 hours ago, phil.g00 said: I think I'd forego this DC efficiency in favour of having the PV available for other things as AC. I agree. Rectifiers are not terribly inefficient at all, especially not the nice synchronous ones. Cyon and phil.g00 2 Quote Link to comment Share on other sites More sharing options...
Coulomb Posted August 27, 2020 Share Posted August 27, 2020 23 hours ago, phil.g00 said: Best thing is to measure it. Definitely. Perhaps a decent clamp multimeter with min-max capability might do it; just measure the maximum start-up current drawn by one phase. ___ 1 Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted August 27, 2020 Share Posted August 27, 2020 4 hours ago, Coulomb said: Definitely. Perhaps a decent clamp multimeter with min-max capability might do it; just measure the maximum start-up current drawn by one phase. Or borrow your existing system's shunt and a min/max voltmeter. Although a trace to show the current decay would be nice, you are probably not interested in the first second, so you can differentiate between inrush and starting current. Quote Link to comment Share on other sites More sharing options...
Gerrie Posted August 28, 2020 Share Posted August 28, 2020 The Yaskawa 18KW drive is rated 38A F.L.C at 380V the running current should be maximum about 20.9A on a healthy pump. Quote Link to comment Share on other sites More sharing options...
Delta9 Posted October 15, 2020 Share Posted October 15, 2020 (edited) On 2020/08/26 at 12:28 PM, ___ said: You can build a three-phase setup with three Multis/Quattros, and put a single-phase supply on just one of them. This is one way to make a 3-phase supply from a single phase supply. Could you please tell us plebs more about this. Sounds very interesting. I have a single phase supply to the Stukki Plass but want to pump water from a 3 phase pump. I dont have the pump yet so this is wide open. I would like to design a system that takes all of this into account. Looking at a DAB pump with inverter (Dab lingo for VFD drive?) that would be a 3 phase pump. So if I could use 3 x Quattros to provide 3 phase to the pump while only having a single phase supply that would be handy indeed. Eventually I will be putting in my own 200 amp transformer but a long ways off that yet as there are so many higher priority things to get done. I am also going to put in PV arrays so ac coupling that to the Victron is probably the way to go, but still nice to be able to pump at night if its possible from a single phase supply to a 3 phase pump. Have I understood this all correctly or is this my wild wishful thinking out of control? Edited October 15, 2020 by Delta9 Quote Link to comment Share on other sites More sharing options...
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