Reduced voltage starter
Reduced voltage starter
(OP)
Does any vendor still sell resistive reduced voltage starters? I seek same to limit inrush surge on a large transformer.
This is 3 phase 208, FLA of ~50A application.
Thus far, I can't find a source: be it new, NOS or refurb.
Many vendors have tried to sell me SCR-based "soft-starters" but when pressed, admit such limits RMS, not instantaneous i. [I'm not sure how a SCR-based system could ever do so...]
This is 3 phase 208, FLA of ~50A application.
Thus far, I can't find a source: be it new, NOS or refurb.
Many vendors have tried to sell me SCR-based "soft-starters" but when pressed, admit such limits RMS, not instantaneous i. [I'm not sure how a SCR-based system could ever do so...]





RE: Reduced voltage starter
RE: Reduced voltage starter
[120V NTE 40A source]->-[120/208:277/480v@15KVA]-->--[480:208/120@112.5KVA]
It's the latter I'm concerned about.
I have resistors [aka immersion heaters] staked out, and as for time delay, all we need is 3-5 cycles. That's less then the pickup time of an undelayed contactor...
RE: Reduced voltage starter
RE: Reduced voltage starter
RE: Reduced voltage starter
I think these guys might also deal in AC reduced voltage starters. Look on their projects page (they advertise that they refurbish old starters). It doesn't hurt to ask.
http://www.dccontactors.com/index.html
These guys might be able to build you something.
http://www.milwaukeeresistor.com/specialty.htm
Just curious, why don't you just build your own? They're pretty much dead simple. We used to stretch out larger fence springs and mount them to a phenolic board for our reduced voltage starters in the elevator business.
RE: Reduced voltage starter
Interesting; I was just starting to see where the DC SSR technology now is; can we switch the 230VDC/~5A PV output with same or do I need relays.
That was my plan. And your reference to the resistor company is a big help. (Closer than the company I found in India; but not as cheap as the 2500W@120V heaters I found for $2.95 each.)
But the electrician is not at all sure how the AHJ will react to such, and recommended we find something looking more everyday ordinary. [I leave it to you code gurus to expound on what rules apply inside a closed 208V switchboard.]
RE: Reduced voltage starter
It's DC, I don't see why not...
Well, if you get it from a company like Milwaukee Resistor, then they will be able to point you in the right direction. But basically you will have to fuse it and enclose it inside a case or behind a plexiglass cover to keep it out of way of wandering fingers.
Milwaukee Resistor might also have a UL inspector available to look over the design, that's what one company I used to work for did. He would come out and inspect our panels before shipping them off to the jobsite.
RE: Reduced voltage starter
AC is easy to switch; use a SCR/Triac and it turns itself off for you half a cycle later.
With DC, it's a lot harder. I guess you now use high power IgFETS that didn't exist when I took the course. For years, there were GTO's but they are hardly "easy" to shut off.
RE: Reduced voltage starter
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Reduced voltage starter
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Reduced voltage starter
Oh, I likely will, if they makes ones sized for our use. But the immersion heaters are cheap enough to use/abuse while testing.
What would be best would be something like http://www.milwaukeeresistor.com/brenclosures.html I suspect.