Re: DYN4 Power Components
Hi,
Quote:
I would expect not to need more than 45A for each component? It makes me wonder what good the breaker is doing since it wouldn't protect anything from letting out the smoke.
It wouldn't, and really that is not a circuit breakers job. It will open trip and pretty smartly if a fault develops in one or more of the drives where the fault current is high. Expecting a circuit breaker
to trip with a continuing but modest overload it not that realistic.
You would be better off with a 16A breaker for each drive. That would give you more protection, but even still most 16A circuit breakers will hang in there at even up to 25A for many seconds.
The drive itself has over-current protection which is very much more accurate and very much faster. If the drive can't protect itself from overload then a circuit breaker sure cant.
Craig
Re: DYN4 Power Components
Hi,
Quote:
I would expect not to need more than 45A for each component? It makes me wonder what good the breaker is doing since it wouldn't protect anything from letting out the smoke.
It wouldn't, and really that is not a circuit breakers job. It will open trip and pretty smartly if a fault develops in one or more of the drives where the fault current is high. Expecting a circuit breaker
to trip with a continuing but modest overload it not that realistic.
You would be better off with a 16A breaker for each drive. That would give you more protection, but even still most 16A circuit breakers will hang in there at even up to 25A for many seconds.
The drive itself has over-current protection which is very much more accurate and very much faster. If the drive can't protect itself from overload then a circuit breaker sure cant.
Craig
Re: DYN4 Power Components
It's not that I was expecting it to be the first line of defense (as you correctly pointed out it's unsuited to that purpose), but a vastly oversized breaker wouldn't trip even if everything else in the cabinet let out the smoke, which isn't useful either. I was asking more to try to make sense from DMMs recommendation.
I should note that it explicitly states, "...select double the rated MCCB...". Since it's already doubled the rating for a single drive (see second screenshot), doubling it for three drives (15a each) would mean I'd need a 90a breaker.
Re: DYN4 Power Components
Hi,
well by all means follow DMM recommendations, but I agree they don'y make sense to me.
I use 750W Delta B2 series servos which are quality/price/performance very similar to DMM. I have one 6A 'D' curve breaker to each servo drive (five of them).
The reality is that a 750W servo will draw less than 0.1A from the AC supply for 99.99% of the time. Every once and a while it will draw big currents, but very seldom and usually for very brief
periods. A 'D' curve breaker accommodates these short duration current pulses. In the 2.5 years of operating my machine I've never had a breaker trip, and now that I am familiar with how they
work and the internal protections they employ, short of a catastrophic fault nor do I expect a breaker to trip.
Craig
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Re: DYN4 Power Components
Do you have a noise filter, line reactor, and contactor between each breaker and the drives, or did you go directly? I'd be interested in how you wired your ESTOP to cut the power to the drives (before or after breakers)?
5 Attachment(s)
Re: DYN4 Power Components
Hi,
I have a two stage EMI filter and a line reactor on the AC input side of the VFD.
I have another two stage filter on the AC supply for the PC, the motion control electronics and their associated power supplies.
I have no filters or line reactors on any of the servos.
I do not have a contactor. I get into huge arguments with people over this. Standard practice is that if you hit the <Estop> button not only does the machine stop but all, or most, of the machine
de-powers. I've never done that. I rely on the motion control responding and shutting down the machine if I hit <Estop> In the 13 years I've been doing it my controller has
always instantaneously stopped whenever I hit <Estop>, and therefore I don't think I need a contactor.
Don't worry there'll be plenty of people who tell you I'm wrong...but unless they can get themselves to New Zealand to confront me about it I can tell them to f****off.
I have just bought a new spindle, its in customs as we speak. It requires a three phase 400VAC VFD, so I will have to decide how to do this. All my existing spindles, servos and motion
control is 240VAC. Whether I have two supplies (400VAC and a separate 240VAC), or I have a 400VAC supply but with a neutral so I can pick of 240VAC, or just a 400VAC supply and
a transformer to get 240VAC for all the servos etc is yet to be decided.
That in turn leaves open the question of a contactor. If I have two supplies then it would be almost mandatory, I mean if I turn off the 400VAC supply then I'd sure want the 240VAC supply to shut
down to before I started poking my finger in there? On balance I think I will have a contactor, and that would in turn allow me to isolate the machine easily. What I will not do is have the
<Estop> button do it, but I would have another, albeit smaller red button to isolate the machine.
My electrical setup is' as rough as guts', its just grown and morphed as I've added new bits. Its coming to something like its final state with regard to equipment, so over the course of the
year I will get around to a proper cabinet. At the moment all the bits are screwed to plastic breadboards, I s***t you not, they are sold for use in the kitchen, just cheap plastic as far as I' concerned.
I can pull each one out on a sort of rack to work on it or add something or whatever.
I've been using it this way since I built this machine (2.5 years) and have not electrocuted myself, my pets, my neighbours, my neighbours pets. Shame really, I've got one neighbour who deserves a good zap!
Craig
Re: DYN4 Power Components
Hi,
at the moment I have five servo drives, one for each axis. I have another servo drive for my servo driven spindle that I use for steel, and I have a small VFD for my 800W 24000rpm spindle,
plus the AC distribution stuff including breakers, line reactor for the VFD, and the two EMI filters.
In the near future I'l have another larger 7.5kW VFD for my new spindle. I'll probably retain the little VFD to drive a variable speed coolant pump. In the medium term I'm building another servo
driven 'steel' spindle, say 2000rpm but 20Nm continuous and 100Nm peak. So I'll need space in the cabinet for that too.
All-in-all I need quite a bit of room in the cabinet. You always seem to be adding new bit and pieces and it all adds up.
Craig
