Bridgeport motor ID

[joe_m]

You really don't want to go that route - if you need to kill power to the VFD you'll be running to the power panel.
It's not hard to install a 220V outlet or have one installed - run it in the wall or in conduit if you have to.
Once you've got an outlet near the mill you just buy a matching plug and a few feet of cord from an electrical supply - total cost for plug/cord is less than $5. It takes 5 minutes to hook the cord to the plug and the cord to the VFD and then it's done right and if you did have an emergency -
say you somehow messed up a simple operation by forgetting to tighten something, and big hunks of metal were suddenly spinning around as a two ton machine started dancing across the floor and you found yourself lowcrawling across that samee floor for the exit, you could just reach up and yank that cord rather than trying to sprint across the workshop to the panel before getting crushed like Wiley Coyote under the falling safe....

And yes, it happened to me. On the lathe. There's a blow-by-blow description somewhere on this forum....



Joe

 

[Ulma Doctor]

Mike, So I can run regular 12-2 w/ ground from the breaker and use the white wire as a hot wire instead of a neutral?

yes, just as long as you keep note that you are wiring a 220v circuit!
mike)

 

[Ulma Doctor]

no I don't have outlet. Yes pretty much straight. Maybe a switch in between if I need to

LEEQ,
you may wish to consider a disconnect of some sort, even if it is a simple plug/connector arrangement.
there are mini twist lock plugs available at lowes, home depot,ace hardware,etc that aren't expensive and easy to install.
mike)

 

[LEEQ]

yes, just as long as you keep note that you are wiring a 220v circuit!
mike)

Cool. So when I wire it up w sfc tomorrow can I take some readings that will indicate HP?

 

[Ulma Doctor]

Cool. So when I wire it up w sfc tomorrow can I take some readings that will indicate HP?

yes sir through osmosis we can derive the hp accurately .
we are going to have the second part of the equation when we get an amp reading and a voltage reading:

here's watt's law: P(power or watts)=V(volts) X I(current in amps) for example...
P(watts) is unknown...
we measure the incoming voltage between poles, in this case we'll use 220v
you would run the motor, taking an amperage reading. let's just say 6.0 amps for giggles...
P=220 X 6.0
P =1320 watts
now, knowing that 1 Horsepower is equal to 746 watts and 1 watt is equal to 1/746 of 1 hp ...
we take P 1320/ 746 = 1.7694369 HP or just over a 1 3/4 hp motor @ 6.0 amps....

let's try 5.0 amps just for fun....
P=220 x 5.0
P=1100 watts
1100/746= 1.4745308 HP or just under 1.5 HP @ 5.0 amps

i hope i'm not sounding redundant, i'm merely trying to explain things so that they are clear to you.
mike)

 

[Ulma Doctor]

i know someone may chime in on my last post with that's the incorrect way to determine 3 phase HP
i'm fully aware of the formula to exactly determine HP output for 3ph motors, but in case others don't here it is....
I=volts, E= amps

I X E X EFFICIENCY X 1.73 X POWER FACTOR / 746

EFFICIENCY= 746 X HP/E X I X PF X 1.732

POWER FACTOR= INPUT WATTS/E X I X 1.732

i use the formula posted earlier ONLY WHEN i don't have to be to the gnats @ss
even the formula used on the earlier post is accurate to .002 hp at 220v 5.0amps
but if your worried about better than .002 hp you don't need my postings anyway.
i hope the info helps someone!
mike)

 

[LEEQ]

ok, where do I take tohse readings? At the pairings? Do I ground one lead to the motor case and test one pair with the other lead? Or do I test with one lead on pairs 1,7 and one on 3,9 as pair 2,8 is only used on start up?

 

[Kennyd]

Take a look at this picture Lee, I have 12-2 from the panel to a 2-pole switch (made to disconnect both sides of the 220v circuit), then from the switch to the VFD in that box mounted under the VFD. You really should have a switch so the VFD is not powered all the time.



Once you get all that setup and installed, we can help with the low voltage drum switch wiring.

 

[Ulma Doctor]

ok, where do I take tohse readings? At the pairings? Do I ground one lead to the motor case and test one pair with the other lead? Or do I test with one lead on pairs 1,7 and one on 3,9 as pair 2,8 is only used on start up?

you can take the readings at the pairings, or anywhere on the the load lines to the motor.
you will bet testing between power legs, testing hot legs to ground is unnecessary unless you are just seeing if there is voltage present.
we're gonna need the readings after the motor has started, the initial inrush of current will just show up as a large sweep of the tester if you are using an analog meter, a digital meter will show a large jump in voltage as well then calm down to a readable voltage.
you may test between winding pairings 1,7 to 2,8 record your findings, then 2,8 to 3,9 record your findings.
you will then need either a clamp on amp meter, or an amp meter wired in series with your load and record your readings.
i prefer the clamp on type, they can be used without having to open the circuit.
all three pairs have continuous voltage while the motor is in operation,
treat those wires like they are cobras waiting to bite you while that motor is running.
if you can collect the readings it will be easy to calculate your motor's hp
let me know if you need further clarification, i could even make a video for you if necessary.
i'm here to help out!
mike)

 

[LEEQ]

Not too clear on the amp thing. I have an amp setting on my digital meter. I don't however know where to stick the probes to test amperage.