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VFD
- Thread starter kd4gij
- Start date
- Joined
- Dec 8, 2013
- Messages
- 2,651
With that small a motor you might as well stick with 110.
- Joined
- Nov 16, 2012
- Messages
- 5,596
In general, when you have 220, the current draw on each leg of the conductors is half of what 110 would be. In some cases, this prevents circuit breakers from tripping and prevents the lights from dimming when you hit the switch. For a 1/2 HP motor, the difference is so small, it won't make a big difference unless you're running the circuit all the way to the far end of your property
.You'll like the smoothness of a 3 phase motor. Cat's meow...
Ray
- Joined
- May 7, 2013
- Messages
- 216
In general, when you have 220, the current draw on each leg of the conductors is half of what 110 would be. In some cases, this prevents circuit breakers from tripping and prevents the lights from dimming when you hit the switch. For a 1/2 HP motor, the difference is so small, it won't make a big difference unless you're running the circuit all the way to the far end of your property
You'll like the smoothness of a 3 phase motor. Cat's meow...
Ray
Ray is right in what he has said but if you are adding machines or have more machines 220v is cheaper to run. With all of my tools I try to run 220v be it 1ph or 3ph and in my most active times in the shop running the lathe 5hp, my welders, and other tools it cost me about $20 a month which I don't think is to bad.
Todd
- Joined
- Feb 7, 2011
- Messages
- 5,039
I am still trying to deside to go with 3/4hp brushless dc motor or the 3 phase. My air compressor is the only thing on 220v right now. My G0704 is 110. and my lathe that has died was 110 dot shure of size as it is oooold and big. No lable but it has an external start compasiter mounted in a box with an open air relay with fowered and reverse switch. If I stay with a single phase motor I would need to get a drum switch. so the cost would end up the same.This is the motor I am looking at. Thay are out of 3/4hp.http://dealerselectric.com/default.asp
- Joined
- Nov 16, 2012
- Messages
- 5,596
I don't have much experience with DC motors in terms of powering shop machines. I have used VFD for a long time. The only problem I ever had with a VFD is reading the manual and getting the initial setup working. Most of the manuals are poorly translated. Aside from that, they've all been reliable.
A few random thoughts and questions that others will hopefully comment on:
DC motors produce more torque at low speed and it drops off at higher speeds. I'm curious about how that effects your machining operations. With the old VFDs, they didn't control torque at low speed too well but, newer units do a pretty good job of pumping current at low speed and keeping the motor strong.
Most everyone I know who has a DC motor, has had electrical problems with the DC controller. Various different problems experienced by several people I know or work with. They're always blowing fuses on the board or replacing resistors etc... What's up with that? Is that common or just problems due to junky controllers?
Is it my imagination or, do DC controllers cost WAY more than VFDs? (Maybe the expensive ones don't screw up as much).
DC motors seem to be 10 times heavier than equivalent single or three phase units. I presume the magnets are pretty heavy.
Depending on the DC voltage range, the connecting wire becomes substantial when you get out of fractional horsepower range. Hookup wire is usually a minimum of 8 gauge for lower voltage units.
Q: What's the tradeoff with higher voltage DC units vs lower voltage DC units? Yes, I know Ohm's law... What I'm after is the practical difference in terms of performance and application.
I guess I've stayed away from DC motors because of all these things. Maybe someone can enlighten me. All I can say, is that all my 3 phase motors and VFDs have done nothing but give me rock solid performance.
Ray
- Joined
- Oct 10, 2013
- Messages
- 19
Go with the 3 phase if possible. Todays VFDs have good low end starting torque and you can set your accel/decel parameters for nice smooth operation. You also can easily set the overload parameter to match your motor. Set the maximum speed parameter to "full tilt buggy" for those high speed operations. Distribute the current over three wires... Ah life is good!
Wish I had 3 phase in my shop.
--Mike
Wish I had 3 phase in my shop.
--Mike
- Joined
- Sep 11, 2012
- Messages
- 329
Here I am again. The great naysayer.
Equipment is not cheaper to operate at a higher voltage. Period. Volts times amps equals watts. Guess what you pay for? Thats right kilowatts. 746 watts make a horsepower. Run a one horse motor for an hour and you get charged for about 1 kw of power usage.
Double the voltage and you halve the amperage. Therefore the possible source of this erroneous assumption.
a 1hp 3 phase motor, by book draws 3.6amps @ 230 volts, or 1.8amps @ 460 volts.
3.6 x 230 = 828 watts
1.8 x 460 = 828 watts and watts are what you pay the man for.
828 watts minus 746 watts equals the loss of efficiency of the motor due to slip, heat, power factor, hysteresis losses etc. You get to pay for it with no return.
Bottom line, the operating cost is the same regardless of voltage applied. Why do 3 phase motors draw less then 1 phase motors of equal horsepower? Three phase is just more efficient. Less in--same out.
Along those lines, are why I do not understand the supposed efficiency of a Rotary Phase Converter. If you have to idle along a 5hp motor to run the 3hp motor on your lathe how can this be more efficiently, and cheaper to operate through time than just buying a Variable Frequency Drive as some profess? Seems to me running eight horsepower is running eight horsepower no matter how you stack it. Besides that how about all the built in freebies the VFD gives you for no extra charge? And a lot less gear to maintain. I am way off track now, but ponder on it and give me an answer. I am always ready to learn a new trick.
Equipment is not cheaper to operate at a higher voltage. Period. Volts times amps equals watts. Guess what you pay for? Thats right kilowatts. 746 watts make a horsepower. Run a one horse motor for an hour and you get charged for about 1 kw of power usage.
Double the voltage and you halve the amperage. Therefore the possible source of this erroneous assumption.
a 1hp 3 phase motor, by book draws 3.6amps @ 230 volts, or 1.8amps @ 460 volts.
3.6 x 230 = 828 watts
1.8 x 460 = 828 watts and watts are what you pay the man for.
828 watts minus 746 watts equals the loss of efficiency of the motor due to slip, heat, power factor, hysteresis losses etc. You get to pay for it with no return.
Bottom line, the operating cost is the same regardless of voltage applied. Why do 3 phase motors draw less then 1 phase motors of equal horsepower? Three phase is just more efficient. Less in--same out.
Along those lines, are why I do not understand the supposed efficiency of a Rotary Phase Converter. If you have to idle along a 5hp motor to run the 3hp motor on your lathe how can this be more efficiently, and cheaper to operate through time than just buying a Variable Frequency Drive as some profess? Seems to me running eight horsepower is running eight horsepower no matter how you stack it. Besides that how about all the built in freebies the VFD gives you for no extra charge? And a lot less gear to maintain. I am way off track now, but ponder on it and give me an answer. I am always ready to learn a new trick.
I would do the 220 wherever possible. Even though it is the same total watts, spreading it across 2 legs is easier on equipment.
Dave
- Joined
- Nov 16, 2012
- Messages
- 5,596
As for 3 phase being less costly to operate, I'm in the same school of thought as rdhem2. 3 phase motors are slightly more efficient because it's a better balanced system and also, does not require capacitors. At one time in my life, I probably studied/analyzed the exact theoretical efficiency difference -but my dual major in physics and EE was long ago. I'll take a guess that the average 3 phase motor is a total of 3-6% more efficient. In some cases, that could add up to a lot, but in small shops, leaving your shop door open on a cold day will cost you more in heating fuel than all the savings from the motors after a week of use.
Also, if you use VFDs, you gain the benefit of controlling the motor w/3 phase but lose about 5-10% efficiency in the VFD alone.
I have heard that in some areas, 3 phase power is billed at favorable rates vs. residential. In this regard, you need to know "The Man's" fee per kWh. Around here, it could be anywhere from 4.5 to 11 cents per kWh depending on time of day -and more importantly, how much money the State needs to collect in energy taxes that week.
Ray
Also, if you use VFDs, you gain the benefit of controlling the motor w/3 phase but lose about 5-10% efficiency in the VFD alone.
I have heard that in some areas, 3 phase power is billed at favorable rates vs. residential. In this regard, you need to know "The Man's" fee per kWh. Around here, it could be anywhere from 4.5 to 11 cents per kWh depending on time of day -and more importantly, how much money the State needs to collect in energy taxes that week.
Ray