I see the info that only WYE (Star) connection is supported, but then in the same paragraph it states Delta loads are supported. Is this contradictory to the statement or am I misunderstanding the explanation? I only have single phase input, so shore power or generator connection doesn’t apply for me and I plan to connect a motor in WYE connection, but would like to know about this Delta load statement. Perhaps they meant Resistive load in Delta is supported but not Inductive loads. That would make more sense, and if so, a correction to the document is needed.
I am not commenting on Victron here and have never read the document you refer to or have any knowledge specific to starting 3 phase AC Motors…
However just talking about the motors, in general…
A 3 phase induction motor will be rated for two voltages, star and Delta.
the relationship between those voltages is Sqrt(3)
In the UK, and ‘most’ other places I expect, you would typically expect to find motors of 2.2kW and below rated at 230/400. whilst bigger motors are generally 400/690
The first number is the Deta configuration
Having and using a 690V supply isn’t ‘normal’ but using a 400/690 on a 400V supply is absolutely typical. Before VFD’s became typical Star/Delta starting was the way to gat a big motor online.
Connecting 400V to a 690 configured motor got it spinning whilst somewhat limiting the maximum current and once it was running it would be switched into Delta, giving it additional torque and allowing it to run as intended.
In general an induction motor will draw significantly more than its Full Load Rated current when starting up 5 or 6 times FLC isn’t uncommon.
A properly setup VFD, or even soft starter, will limit this to typically around 2.5 times FLC whilst ramping up but take longer to accelerate the motor to its rated RPM.
To answer you question you need to be specific about your load, mechanically, the motor attached to it what motor control you are proposing, even if that is just DOL, and your inverter setup.
Note that the power factor of a starting motor is usually terrible, even with correction, and that results is potentially much higher currents than you might expect.
I expect there is Victron guidance on this matter which will deal with starting requirements and reactive energy at the very least.
I do not know what the guidance is and I am not about to guess, save to say it isn’t a simple problem and you will probably need to have a grasp of the underlying principles to adequately apply it.
Bear in mind… The same motor with different inertial mass attached will behave differently, taking longer, and more energy, to accelerate.
Hope that helps, and I am sorry I cant be specific.
Al
This slide, and diagram, represents the source. note the Inv1, Inv2, Inv3.
It supports delta connected loads.
Yeah, I don’t know who put the drawings on there and I can’t find this document online. I downloaded it several months ago. That’s also how I see it. I just wanted more clarity about the load side. I started to second guess the explanation after reading and assume each statement was only discussing input, with the last sentence only is about loads.
Thanks, but this is Victron specific with a 3 inverter setup.
Also, others mention delta not being supported. I guess it is misunderstood by many. Here is another thread: Running a three phase delta-motor setup
Not supporting Delta is talking about the inverter configuration and generating/inverting in Star is typical, even on huge grid scale systems, all be it at much higher voltages.
Most transmission lines do not have a neutral, star point, just 3 conductors, however they are referenced to ground with transformers, at least at the point of use, if not at regular interval along the line.
When inverting, a Victron inverter, at least the ones I am aware of, connects its start point/neutral to ground. when connected to an AC input there is an option, the ground relay, to break that connection and rely on the one that the grid/supply/generator is providing.
How a specific system is configured largely depends on your kit, and the requirements of you local electricity supply regulations. In the UK you are normally looking at TNS / TNCS or TT, the latter being very different in its function and requirements to the two former configurations.
Generally, very generally, a relatively small inverter or generator will not be able to supply sufficient current to open an RCD quickly enough, or even at all, to satisfy prescribed disconnection times in the event of an earth fault. Thus a TT system utilising some form of RCD/RCBO/ELCB/GFI… it depends where you are will be required. In all cases fault current is either measured, or implied by summing phase and neutral currents, and the circuit is opened when some fault threshold is reached.
NB. This is just a very basic explanation there other systems and regulations vary significantly depending on where you are.
Al
I get that, my point was that you probably needed to understand the basics to interpret the Victron specific stuff.
Can it drive ‘a’ Delta load, based on the quote it would seem so, and there is nothing electrical that I am aware of that would preclude that.
Can it drive ‘your’ load…
Very different and important question that will need detail to answer.
Just trying to give you the bigger picture and point out a couple of pitfalls!