Apr. 29, 2024
To answer this question, we must first understand the difference between the efficiency of a high-voltage motor and a low-voltage motor of the same power.
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The fundamental difference between high-voltage and low-voltage motors is that the rated voltages of the two are quite different, which also leads to a large difference in the insulation structure of the stator winding between the two. However, from the comparison of the efficiency and performance of the whole machine, what is the relationship between the two? This is a question raised by a concerned motor practitioner. Today, we will communicate with you based on the national energy efficiency limit standards for high and low voltage cage motors.
GB18613 is the energy efficiency limit standard for low-voltage motors, and GB30254 is the energy efficiency limit standard for high-voltage cage motors. Both standards are mandatory standards.
Comparing the advantages of high-voltage motors and low-voltage motors, for high-power motors, due to the limitations of low-voltage motor manufacturing process and cost, high-power motors are more likely to choose high-voltage motors; motors with a power of about 200kW include low-voltage motors and high-voltage motors, but from Comparing the energy efficiency limit requirements of the two efficiencies, it is difficult to define which motor is more energy efficient.
Therefore, when selecting high-voltage and low-voltage motors, the limitations of conditions also naturally limit the degree of freedom of selection, but from the perspective of manufacturing, the development of high-efficiency motors is more conducive to the improvement of the overall energy-saving effect.
If the motor of the same power, the output power of the higher voltage is greater than the output power of the lower voltage, if the same 15KW motor, three-phase 380v and three-phase 220v voltage, then their power is the same
Since the power is the same, the power consumption will not be too much. Generally speaking, a high-voltage motor has a small current, and the coil generates less heat, so the power consumption may be relatively small. But not absolutely! If the coil wire of the low-voltage motor is thicker, the contact flux of the silicon steel sheet is higher, and the load and torque matching are better, the power consumption may be less than that of the high-voltage motor, because the power factor is higher, the current is lower, and the heat generation is lower. The key is that the ratio of electric power to shaft power is higher!
Unless the high-voltage motor of thousands of volts, the motor voltage is generally higher than the lower one, which is smaller, cheaper, and more efficient!
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Any advantage to higher voltage motors?
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MVPs
(Chemical)
(OP)
21 Mar 19 14:54Hi,
I am trying to figure out what type of motor should I use for the equipment for the pilot I design.
Is there any advantage to 575V 3p motor over 440V 3p? I am talking mostly about low output motors, up to 10kW.
Will there be any advantage for 150kW equipment?
Thanks,
Ron
(Electrical)
21 Mar 19 18:14The most advantageous will be to use a motor that matches the available voltage.In the US you may not find many 600 Volts supplies (for 575 Volt motors), while in Canada 600 Volts is a standard voltage.There are still a lot of 480 Volt systems in Canada but for many years the utility standard has been 600 Volts. Some plants use 480 Volts but source it with their own transformers.Some Canadian plants have dedicated 480 Volt systems for heat tracing only, not available for motors.You won't easily find any 440 Volt, 60 Hz motors. The standard motor voltage is 460 Volts (for use on 480 volt systems).For Canada, 575 Volt motors.For the US and some Canadian plants, 460 Volt motors.
Bill
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"Why not the best?"
Jimmy Carter
(Chemical)
(OP)
21 Mar 19 18:31Thank you, since I need a DC power supply, that I could only find at 480V, I figured I will have to buy a transformer anyhow, so I might as well expand the available motors that I can use.
(Electrical)
21 Mar 19 21:45If you use an open delta autotransformer you will be able to input either 480 Volts or 600 Volts (through different input connections) and be able to run either 480 Volt or 600 Volt equipment. (460 Volt or 575 Volt motors)There are other solutions but in many instances theis the cheapest.
Bill
--------------------
"Why not the best?"
Jimmy Carter
(Electrical)
22 Mar 19 00:41You can get more torque by increase the current or the amp turns. Higher voltage let you use thinner wire which you can use to create more turns when you wire the motor.Higher voltages usually means the connection. To the grid is stronger.Lower losses due to needing to draw less current to get the same torque.
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If you can't explain it to a six year old, you don't understand it yourself.
(Electrical)
22 Mar 19 01:26If you give us a little more information we can give better answers. Is your market local, US, Canadian, US and Canadian, world wide?What is the HP or current draw of the components that you will use?For 150 KW, match the available voltage.
Bill
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"Why not the best?"
Jimmy Carter
(Electrical)
22 Mar 19 01:28HH - All your points are incorrect.OP - At that 10 KW range, any low voltage will work. Your only criteria is what is the readily available voltage at your location.Muthu
(Electrical)
If you are looking for more details, kindly visit Speed Regulation of Synchronous Motor.
Suggested reading:The general point to higher voltage motors is that you can wire them with smaller less expensive wire that is rated for half of what the lower voltage motor current would need. Copper wire is no longer cheap.
Keith Cress
kcress - http://www.flaminsystems.com
(Electrical)
22 Mar 19 09:18The counter-argument is that at higher voltages on relatively small machines you can end up filling a large percentage of the available core slot area with inactive insulation material, where at lower voltage you can get higher percentage fill with active current-carrying (i.e. torque-producing) conductor.
(Electrical)
22 Mar 19 11:13But Scotty how does that matter since 90% of motors are dual voltage?
Keith Cress
kcress - http://www.flaminsystems.com
(Electrical)
22 Mar 19 11:28For random wound LV motors, the winding insulation is practically almost the same from 200 to 600 V and so the copper fill factor is almost the same over this voltage range. The insulation starts to affect the slot fill factor (and hence the frame derating) from 3 KV onward for form wound coils.Muthu
(Chemical)
(OP)
22 Mar 19 12:17Well, this is confusing...So if I understand correctly, there shouldn't be any difference for small motors?The autotransformer seems like a great option for us, I will check it out.I was thinking of buying those AC to DC converters https://magna-power.com/products/magnadc/ms , several of those will give me the output I need, but they do not have any 600V option.Ron
(Electrical)
22 Mar 19 14:24Edison,Tell me why what I said was not true for motors as they increase in voltage?
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If you can't explain it to a six year old, you don't understand it yourself.
(Electrical)
22 Mar 19 14:45The rule of thumb is when the motor Horse Power is higher than the voltage it is time to run the numbers on a higher voltage motor.Quote (Ron74)
Any advantage to higher voltage motors?
The rule of thumb is when the motor Horse Power is higher than the voltage it is time to run the numbers on a higher voltage motor.If your motors are less than about 500 HP each, don't worry about high voltage.Also, in this instance when we talk about higher voltages we are talking about moving up from 480/600 Volts to 4160 Volts or more.If you are comparing motors in the lab, you can quantify the slight possible difference between a 460 Volt motor and a 575 Volt motor but you are not doing a laboratory analysis. You, as I understand it, are selecting a motor to purchase.MATCH THE MOTOR TO THE AVAILABLE VOLTAGE.As an example; If you select a 575 Volt motor because of greater efficiency over a 460 Volt motor, you will need a transformer which will erase any savings in initial motor cost and running efficiency many times over.The perceived advantage of a 600 Volt motor over a 460 Volt motor is a fine point.The added losses of a transformer to run a 575 Volt motor with a 480 Volt supply is a GROSS point.You mention a DC power supply and a 150 kW load as well as motors below 10 kW.You may have unasked and unanswered questions in addition to motor voltage.What are you designing/building?Bill--------------------"Why not the best?"Jimmy Carter
(Electrical)
22 Mar 19 14:50Ron74; Lest the voltages that I quote are confusing:In North America standard SUPPLY voltages are multiples of 120 Volts;120 V, 240 V, 480 V, and in Canada, 600 V.In North America standard MOTOR voltages are multiples of 115 Volts;115V, 230 V, 460 V, and in Canada, 575 V.
Bill
--------------------
"Why not the best?"
Jimmy Carter
(Chemical)
(OP)
22 Mar 19 15:04As I said, I am in Canada and have a 600V supply to the plant.
I cannot find any 600V AC to DC converter so I will have to use a transformer. And this is a large part of the production costs, so I so should I invest more time on finding one or asking for a custom design?
I've read in another post somewhere that 575V motors are not common in industrial applications here, most of my experience is with the European voltage. 600V is used mostly for commercial application and municipal wastewater, I do not know if this true.
I will get on a later stage an electrical engineer to design, but I need to order the motors before.
(Electrical)
22 Mar 19 15:54Warross,Is that rule of thumb for certain voltage ranges? For a 480hp motor being fed by 480, I am getting near 600A and that would require 1000 mcm cable if you didn't bundle.
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If you can't explain it to a six year old, you don't understand it yourself.
(Electrical)
22 Mar 19 15:58If the utility is supplying the transformer in Canada it will most likely be 600 Volts.Smaller plants generally use the 600 Volts supplied by the utility.Larger plant who typically buy their own transformer must decide what voltage to use.I have worked in plants that were 600 Volts, plants that were 480 Volts, plants that were 600 Volts but also used 480 volts for specific equipment, and one plant that had about a 50/50 mix of 460 and 575 Volt motors and had both 600 and 480 Volts.600 Volts is the standard.480 Volts has a much greater range of available equipment from the US.You should be asking us how to source your DC supply.You should be finding out the supply voltage where your equipment will be used.
Bill
--------------------
"Why not the best?"
Jimmy Carter
(Electrical)
22 Mar 19 16:15HH; Good question. If you are moved to ask that question, then it is time to consider going to 2400 V, 4160 V or higher.Consider the cost of supplying 4160 Volts, transformer, switchgear.Consider the training and abilities of the electricians who will be responsible for the motor. You may have to contract an outside contractor who has higher voltage experience.I remember one installation with a 120:208 Volts supply and a second 4160 Volt supply for one 600 HP A/C motor.I have seen more than one installation of 3000 HP motors where the supply was 13,000 Volt class.It could have been 4160 Volts, but given the number of motors involved and other factors, they designers chose 13,000 Volts.One plant was a total of 36,000 HP (12 x 3000 HP) at 13,000 Volts.One was a total of 48,000 HP (16 x 3000 HP) at 13,000 Volts.The rule does not mean that when the HP exceeds the voltage you must go to a higher voltage.The rule means that when the HP exceeds the voltage it is time to run the numbers. (even at 208 Volts)
Bill
--------------------
"Why not the best?"
Jimmy Carter
(Electrical)
22 Mar 19 19:50Ron74; What do you need for DC? Volts? Current?
Keith Cress
kcress - http://www.flaminsystems.com
(Chemical)
(OP)
22 Mar 19 20:03A patented electrolysis process.
I need to maintain a constant current while the voltage changes with the process.
(Electrical)
22 Mar 19 21:56The thing I find the most interesting is that you cannot find a 600V AC-DC power supply. What are the requirements on the power supply?
(Electrical)
22 Mar 19 22:00My first thought was an MG set with an Amplidyne but those days are long gone, never to return.Quote:
I need to maintain a constant current while the voltage changes with the process.
Are you needing 150 kW DC? Give us a few details and we will make some suggestions.Are you able to share the make and model of DC supply that you are interested in?150 kW DC may be a much bigger issue than motor voltage.Is this a one off, or will you be selling the machines?My first thought was an MG set with an Amplidyne but those days are long gone, never to return.(thnks smoked.)
Bill
--------------------
"Why not the best?"
Jimmy Carter
(Chemical)
(OP)
23 Mar 19 18:19I need to supply current to the electrodes.I will probably be needing several smaller units total around 150 kW.I thought about those PS https://magna-power.com/products/magnadc/ms Ron
(Electrical)
23 Mar 19 19:27Answering Keith's question of a few posts ago -
We don't tend to see dual-voltage machines in Europe, other than the natural dual voltages arising from a star or delta connection. The difference in insulation between, say, a 3.3kV machine and an 11kV machine is significant. Smaller 3.3kV machines are like an overgrown LV machine and often built in a similar manner, where an 11kV machine will almost certainly have formed windings and taped insulation. There's a very different fill-factor in terms of how much dead space exists in the higher voltage machine because of extra insulation. Having skipped back to the the original question where the motors are clearly stated to be LV, this probably is particularly helpful to the OP.
(Electrical)
23 Mar 19 19:53Select a Power Distribution Center or a panel suitable to power all of your power supplies.Use an open delta auto-transformer to drop the 600 Volts down to 480 Volts.You may run your motors on either 600 Volts or on 480 Volts from the panel.You will not be able to connect line to neutral loads to the 480 Volt system, only line to line loads.I have seen this done many times. I have also many times seen situations where 480 Volts was stepped up to 600 Volts with an open delta auto-transformer and then stepped back down to 480 Volts with an open delta auto-transformer.I have also seen situations where 600 Volts was dropped to 480 Volts and then stepped back up to 600 Volts.An open delta auto-transformer is by far the cheapest and efficient way to make small changes in voltage.
Bill
--------------------
"Why not the best?"
Jimmy Carter
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