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3 phase machines with voltages higher than 230/240

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Forum topic by marc_rosen posted 02-21-2015 03:25 AM 1565 views 0 times favorited 18 replies Add to Favorites Watch
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marc_rosen

79 posts in 2643 days


02-21-2015 03:25 AM

Topic tags/keywords: question motors

Hey Gang,
I hope this is the right forum for this query. I was looking at the schematics for the different voltage configurations of the Sawstop Industrial model on line and I noticed for the models with higher voltages- 415, 480, or 600V – they use a transformer to bring it down to 230 for the motor. Is this a typical set up for most 3 phase machinery or is this a convenient way to use one motor (5 or 7.5 hp) to satisfy a wider range of possible voltage applications?
Thanks in advance for your comments and no, I’m not buying a 3 phase Sawstop. (Just curious.) Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"


18 replies so far

View alittleoff's profile

alittleoff

296 posts in 739 days


#1 posted 02-21-2015 04:07 AM

Most industrial motors are 480/208 volts. These can be wired for either voltage by changing the wiring in th motor. Most factories will run the equiptment on the higher voltage due to the savings on conduit labor and smaller wire to run it. Transfers are used seldom to reduce or increase the voltage when it’s not available. Lots of equiptment coming from foreign countries have odd voltage where a transformer must be used. One of the last printing press I wired was 560 volts. It came from Russia. Most of the time commerical buildings have 480/240, 120/208 available to use.
Gerald

View Fred Hargis's profile

Fred Hargis

3935 posts in 1956 days


#2 posted 02-21-2015 12:44 PM

When I had a day job as a Reliability Manager at a plant, it used to irk me no end that the spare motors in the storeroom were pre wired for 240V, and everything in our plant was 480. So during a breakdown it would take someone time to change the motor to 480 before installing it and getting the machine back into service. The time required would only be about 15 minutes for an experienced and/or skilled tech, but might take an hour for someone less familiar with it. Even had a few that tried to install the motor without changing the wiring (grrrr). Anyway, none of our stuff had a transformer of any kind, but life in industry is quite a bit different. I’m surprised that SS would do that (use a transformer). Seems like it’s just something else to go wrong over time.

-- Our village hasn't lost it's idiot, he was elected to congress.

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helluvawreck

23157 posts in 2329 days


#3 posted 02-21-2015 02:29 PM

In our molding plant we had a 600 volt service. It was an old yarn plant. Fortunately you can find 600 volt motors on the surplus market. However, we still ended up installing some transformers to bring the voltage down to 480 and also 240 in some cases. In some cases we ordered new machines with 600 volt motors. In a lot of cases the machinery company would just put a transformer in the control panel to accomplish this.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

View REO's profile

REO

889 posts in 1536 days


#4 posted 02-21-2015 04:05 PM

Much of the new motor control equipment is for a large range of voltages. 200-240, 380-480, 490-632.the incoming power is rectified to DC for the use of the electronics and then output at the proper AC voltage for the use of the motor. We have just received our fifth machine from china originally wired for 380. They used a transformer to raise the voltage from 380 to 480 for the motors. until the last two machines we had to rewire the machines to bypass the transformers. One for motors one for drives and one for control power. The way they wire their stuff is no pick nick!Now For the last two we asked that the transformers be omitted. now we can hook up five wires and go.

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CypressAndPine

62 posts in 1270 days


#5 posted 02-21-2015 04:32 PM

I understand your question. If I ordered a 480V machine it would be nice to get a 480V motor and not a smaller voltage machine with a transformer.

Here are my best guess:

Because of the electronics in a sawstop they make their machines more standard to prevent different electronic control circuits for different machines. I can’t really blame them. I wouldn’t want to get patents and licenses and manufacture 30 different control systems when you could just use a transformer.

With that said, a 5HP machine is 5HP regardless of the voltage, but I hope they advertise it as a 230V machine with a transformer to allow operation on higher voltages.

Maybe I’m right, Maybe I’m wrong

Jacob

-- Cypress Jake, New Orleans

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crank49

3981 posts in 2433 days


#6 posted 02-21-2015 07:33 PM

I am not sure if, or why, SawStop would use a transformer to reduce the 480V power to run a 240V motor.
Most 3 phase motors can be rewired at installation to run on either voltage. In 40 years of working with industrial maintenance departments I have not seen more than a couple single 480 volt motors.

But, I have a theory. And it is just that, my opinion and a theory.
Perhaps the SawStop electronics and brake cartridge can not be changed to run on 480V. The electronic components might not even exist for that voltage at the power level required and perhaps the electronics have to sense and be connected to the motor electrically. So, since they had to put in a transformer for the electronics any way and also had to connect to the motor as well, they just took a 240 volt saw and use a transformer to run it on 480 volts.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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REO

889 posts in 1536 days


#7 posted 02-21-2015 08:54 PM

looking over the manuals for the sawstop I noticed they are for sale to US customers only. Interesting. I could not find a three phase motor available all the literature I could find was for single phase wireing. ONE hot ONE not and a ground or TWO hots and a Ground. if you have a link to further info please post.

View SawStopService's profile

SawStopService

5 posts in 2790 days


#8 posted 06-12-2015 06:52 PM

Just thought I’d add some technical data – I work for SawStop Service. All our motors are power-specific, and our motor control system consists of a switch box on the front of the saw, and a contactor box in the bottom of the saw.
The switch box will run on single phase power, anywhere from 80-240 volts, and it gets its power through the contactor box. If line voltage used to run the motor is higher than 240VAC, we use a small transformer in the contactor to step down the power to run the switch box. (That way we can use a single switch box design.)

The motor itself runs off the appropriate line voltage for its rating, i.e. a 208-240v line voltage is needed to power a “230v” motor, a 460-480v line voltage is needed to power a “480v” motor, a 600v line is needed to power a “600v” motor, etc. The contactor relay, which brings line voltage to the motor, is run by 208-230VAC control line from the switch box.

We don’t use big transformers to change the line voltage going to the motor, we match the motor to the power line. In Canada, you can get 230V, 480V, or 600V SawStops, in USA you can get 230V or 480V.

Clear as mud?

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SawStopService

5 posts in 2790 days


#9 posted 06-12-2015 07:00 PM

By the way, our actual power connection requirement:
120V (110 – 120V) standard house wiring: 1 hot, 1 neutral, 1 ground wire
230V (208 – 240V) single phase: 2 hots and a ground wire or 1 hot, 1 neutral, 1 ground wire
All three phase: 3 hots and 1 ground wire

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SawStopService

5 posts in 2790 days


#10 posted 06-12-2015 07:17 PM

SawStop’s smaller 1.75HP motors (models PCS175 and CNS175) can be re-wired for 115v or 230v – all the others are single-voltage motors.

View bigblockyeti's profile

bigblockyeti

3668 posts in 1183 days


#11 posted 06-12-2015 07:36 PM

Why they would use a transformer for the motor alone is beyond me. It adds cost, complexity and another failure point, all together an inefficient design.

View Fred Hargis's profile

Fred Hargis

3935 posts in 1956 days


#12 posted 06-12-2015 08:02 PM


The motor itself runs off the appropriate line voltage for its rating, i.e. a 208-240v line voltage is needed to power a “230v” motor, a 460-480v line voltage is needed to power a “480v” motor, a 600v line is needed to power a “600v” motor, etc. The contactor relay, which brings line voltage to the motor, is run by 208-230VAC control line from the switch box.

We don t use big transformers to change the line voltage going to the motor, we match the motor to the power line. In Canada, you can get 230V, 480V, or 600V SawStops, in USA you can get 230V or 480V.

Clear as mud?

- SawStopService

bigblockyeti, what part of this is it I don’t understand…isn’t he saying the motors are appropriate for the line voltage?

-- Our village hasn't lost it's idiot, he was elected to congress.

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SawStopService

5 posts in 2790 days


#13 posted 06-12-2015 10:43 PM

Fred has it right.
We only use a transformer to downsize the voltage to the front panel switch box.
We do not use transformers to change the line voltage to the motor.

View marc_rosen's profile

marc_rosen

79 posts in 2643 days


#14 posted 06-13-2015 01:33 AM

Hi Saw Stop Service,
Thanks very much for your explanation. I should have contacted Sawstop directly as you would have ended my curiosity but as I typed above, I was also curious if other machines stepped voltages to satisfy the motor’s needs.
No longer curious, Marc

-- Windsurfing, Woodworking, Weaving, and Woodducks. "Most woodworkers are usually boring holes"

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TopamaxSurvivor

17668 posts in 3138 days


#15 posted 06-13-2015 04:31 AM



Fred has it right.
We only use a transformer to downsize the voltage to the front panel switch box.
We do not use transformers to change the line voltage to the motor.

- SawStopService

Nothing new here, That was common practice 45 years ago when I got in the trade ;-)

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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