New motor and VFD, need advice

[aspenelm]

PF is power factor. Don't know why there is no nameplate amp rating. 8.0amps seems on the high side, because my 3hp baldor motor is rated for 8.2 amps at 230volts. The parameter setup for milling machine are nice to know.

[in2steam]

Originally Posted by bilinghm I am doing the basic programing of the Hitachi SJ200 and have hit a snag. One of the parameters that must be set is referred to as "setting the motor current". The Hitachi manual says that The motor's current rating will appear on the manufactureres name plate. I can find no such current rating. Is there another term for this parameter? Could the equivalent Leeson term be "P.F."? P.F. appears on the nameplate and is shown as 85.2. Bill

PF is power factor, thats a normal nameplate things along with amps and volts. Typical PF is around 80-90% motor depandant. PF is the amount that a motor lags the voltage, typicallly run cap motors have the best PF, but these of course are single phase, you can run some of them with inverters.
Since you answered you own question I don't need too.

chris

[in2steam]

Originally Posted by aspenelm PF is power factor. Don't know why there is no nameplate amp rating. 8.0amps seems on the high side, because my 3hp baldor motor is rated for 8.2 amps at 230volts. The parameter setup for milling machine are nice to know.

Your 3HP motor, electrically speaking only is more like 2.75 HP. Typically a single 3 phase HP is around 3.1 amps on 230 and 1.5 on 460. This also depends upon the number of poles and the design class (a,b,c,d), its duty cycle, Full load RPM and enclousre type(TENV, TEFC, etc). Lower pole motors draw more current, or atleast they tend too, there are always exceptions, and this would be more a rule of thumb. There are alot of gray areas when it comes to rating motors, lots of fudging. The problem with motor ratings is that an engineer determines what the HP will be before the motor is ever made, all test results are determined from that point, sometimes they are way off and have to be rerated, but more often they just go with what they had.


chris

[bilinghm]

I finally got everything hooked up, adjusted and ready to run. The pulley selection I fitted provides 2,500 RPM at the spindle when the motor is turning 3550, the full 60 cycle
speed. So I have been experimenting with this arrangement and the results are very positive. I put a 3/4" endmill in the collet and took some cuts on a big bar of mild steel at 10 cycles. The cuts were fine and the machine performed without protest, plenty of power. It seems that the goal of no belt changes and sufficient power for all operations, low to high speed, has been achieved. On a side note, I eliminated all of the additional pulleys and belts, I run just two pulleys and one belt instead of the previous set up of four
pulleys and three belts. The difference in smoothness is exceptional.

[in2steam]

Thats good to hear, what kind of machine was this anyway?

chris

[bilinghm]

The machine is an Enco 90001 round column mill driil from the mid eighties. Old but stiill working fine.

[aspenelm]

so 10 cycles nets you around 410 rpm at the spindle. so you are using the constant torque setting instead of sensorless control. good to see that it worked out for you.

Originally Posted by in2steam Your 3HP motor, electrically speaking only is more like 2.75 HP. Typically a single 3 phase HP is around 3.1 amps on 230 and 1.5 on 460. This also depends upon the number of poles and the design class (a,b,c,d), its duty cycle, Full load RPM and enclousre type(TENV, TEFC, etc). Lower pole motors draw more current, or atleast they tend too, there are always exceptions, and this would be more a rule of thumb. There are alot of gray areas when it comes to rating motors, lots of fudging. The problem with motor ratings is that an engineer determines what the HP will be before the motor is ever made, all test results are determined from that point, sometimes they are way off and have to be rerated, but more often they just go with what they had. chris

I missed this post, but yes, I figured each motor varies a bit. FWIW, the baldor motor is 1750 rpm, 8.2A @ 230v, TEFC, class F, 182T frame, 1.15 service factor, 87.5% efficiency, 78% PF, and rating of 40C AMB CONT. I have the 3hp SJ200 which gives me 4.3 kVA at 230v, with 11.0 amps cont. output. How much juice can I safely run through the motor? The application is for a woodworking dust collector blower for home use, so it will be intermittent use for up to an hour at a time. I need to get as much hp as I can get from this motor, the blower impeller is rated for around 3500rpm. Sorry to sidetrack, but somewhat relevant.

[Al_The_Man]

This application being a bit different from the likes of a Mill etc, I would think it is probabally critical that you do not exceed the F.L.A. of the motor, If you can get hold of a Clamp on ampmeter you could see what the Maximum present current is at 60hz, this will be with both intake and exhaust as unrestricted as possible,
Then take it up gradually to 120hz and see what the effect on current is.
I would think the tendency for the current to climb will be offset by the increase in impedance.
Any restriction of the intake or exhaust after this should decrease the current proportionately, presuming it is a centrifugal impeller.
Al.

[aspenelm]

thanks al, I will try that when I have the dust collector body assembled and ductwork run.

[in2steam]

If your drive has the setting, turn it to constant HP, since this load is dynamic, they may word it in different ways, vectoring will be of little use to you in that application. As far as "juice" goes, your drive won't really let it get more then it can handle if its set properly, you can fudge the settings but its been my general experience that you can't really fudge the numbers to far outside of what the nameplate states. The motor itself is the biggest limit as to what it will draw, as long as the line voltage is steady(most drives don't increase over rating or input) its only going to draw so many amps regardless of what you try and do with the drive although the drive might let you over volt the motor some. As for over 60 Hz threshold your amps will go up to the roof, it may not be possible to get that motor to 120 Hz, the torque will increase ever rpm faster that motor spins(assuming its a centrifugal blower). When I said what class is the motor your response was with the insulation class of F which is good for your use, but there is also a motor class, in your case I think its C but I am only goin on what you have provided. This would make this motor a compressor duty motor, they respond well to a mild to heavy torque at FLA but don't like over or under speed as much(they are designed to have higher torque so the amps go up), which means this motor will more then likely not like the increase in Hz and result in higher then required amp draw in those areas. If you are doing the Bill Pentz design you may need to switch to a 2 pole motor even at half and 3/4 speed that will not draw anywhere what you need for CFM. I think the clear vue guys are running 5HP 2 pole lesson motors, I could be wrong though. 182 frames like to be torquey motors, your amps indicate also that this motor would be better suited for such, you HP will not go above 3 it flat lines at the 60 Hz threshold torque will only reduce from that point esp bad in dynamic loads. If I were to take a jab at 3 HP you might make it to 75 HZ before preforamce degrades since its 1.15 SF motor.

chris

[aspenelm]

Looks like I have some testing to do. I also have a 3450 3hp motor that would work as well. When I get some results I will start a new topic. And yes, it is a Pentz collector.

[in2steam]

Yeah then I would go with the 2 pole motor, 3 HP nema class B or C would be best(I think 4 is min really for multiple inlets) anything less you will not get the needed static pressure and a suitable vortex, they have tons of info on the clear vue and pentz sites I suggest you read it all, one day off in the future when I get rich (quickly) I hope to build one so let us know. I am hoping to buy the clear vue mini (cv-o6) for a router table I am building after I get done with my mill.
chris