Line reactor selection for singe phase

Adding a line reactor ahead of the PT-355 (20hp) It's on a 125A breaker, when the cnc lathe ramps up it peaks at 105A on the 1ph side. Thing is when its running for the most part I only see 30-50A on the 1ph side on longer cuts, though quick small parts will have it peak every minute.

At first I thought 5% 3ph 100A(cont) reactor, but I just saw a chart indicating when running only 1ph through a 3% reactor it acts as being close to 5%.
Which makes it sound like a 5% would likely act as a 7-8% range reactor?
What I didn't quite 100% figure out is how they act when seeing only about half their rated amperage. Would it be only giving half the impedance %?
So, I guess plain question is for best performance should is stick to the idea of going with a 5%? or go with the chart that says 3% when hooked to 1ph?


thanks

The reactor has impedance that varies only a small amount with current. The 3% on single phase will work similarly to a 5% on 3 phase at same power, simply because there is more current going through it so more drop on the same impedance. I expect that is what they mean. the 3% to 5% difference is close to the 1.73 factor in current.

The 3% should be enough in most cases. You do not want too much drop, it will rob power.

I ended up ordering a 3% 100A/240V unit. I think it acts as a 5% when on 1ph because the middle core gets no power to it which probably makes a difference in the inductance/flux of the core. All coils are rated for the same amperage have it be 1ph or 3ph. Oscilloscope should arrive today, it'll be interesting to see a before and after on the 1ph lines but I probably won't get to that for another week or 2.

SND said:

I ended up ordering a 3% 100A/240V unit. I think it acts as a 5% when on 1ph because the middle core gets no power to it which probably makes a difference in the inductance/flux of the core. All coils are rated for the same amperage have it be 1ph or 3ph. Oscilloscope should arrive today, it'll be interesting to see a before and after on the 1ph lines but I probably won't get to that for another week or 2.

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"Over-thinking" all this, mayhap?

If your budget is as tight as many of us here, forget complex test gear.

Just grab a CHEAP temp sensor and mount it to the inductor. Time is going to pass, regardless, so you can make pencil notes of the temp before power-up, and periodically as work progresses.

The 'scope will show you what is still leaking past it. The temp-rise will klew you as to whether it is being pushed to its limits (doubtful) or not even close (probable).

No need to do complex math just because you CAN, nor to spend a fortune. This s**t mostly "just works" because serious engineering, complex math, and comprehensive testing has already been DONE by those who ship such goods.

Not too worried about budget, if power Co said for $50k I could get real 3phase in here I'd sign that cheque right now. But since that ain't gonna happen, its long overdue time that I be able to better monitor these things, find when issues start to arise and minimize the risk.
The reactor is only about $600 in Canadian pesos, need about 6' of new wire and we'll see the before and after on the scope.
Doing it again i'd have just used one of these to slightly drop my incoming voltage to the 230-235v range instead of that big delta/wye transformer that is after the PP now, but eh, live and learn.