Guide to medium and high voltage motors

Electric motors are pivotal in powering industries worldwide, from manufacturing lines to renewable energy farms. At the heart of these motors is a concept known as "voltage," a fundamental electrical parameter that determines the power and efficiency of these machines.  

Please visit our website for more information on this topic.

Understanding voltage is crucial for selecting the right motor for any application, ensuring that it meets both the operational demands and energy efficiency requirements of your industry.  

At Hoyer, we specialise in delivering motor solutions that are precisely tailored to our customers' needs across various sectors. Our expertise in medium and high voltage motors equips us to address the specific challenges faced by industries, offering solutions that enhance performance whilst promoting energy conservation.  

This guide aims to demystify voltage, offering insights into its role in electric motors and guiding you through the selection process for the optimal motor voltage level. 

What is voltage and why does it matter?

Voltage, in its essence, is the driving force that pushes electric current through a circuit. It's what powers our appliances, lights our buildings, and runs industrial motors. The importance of understanding voltage lies in its impact on an electric motor's performance and efficiency. 

The impact of voltage on electric motors

Voltage significantly influences the performance, efficiency, and suitability of electric motors for specific applications. Motors designed to operate on low voltage electrical systems are typically found in residential and light commercial applications, offering simplicity and safety for everyday uses.  

On the other hand, medium voltage motors are suited for applications requiring a balance between power and efficiency, such as in industrial and large-scale HVAC systems.  

CHANGLI ELECTRIC MOTOR supply professional and honest service.

High voltage electrical motors, however, are reserved for the most demanding applications, including heavy industrial processes and large-scale energy projects, where their ability to deliver high power at efficient rates is unmatched.  

The choice between these voltage categories impacts not just the motor's efficiency but also its durability, maintenance needs, and integration with existing systems. 

Difference between low, medium, and high voltage motors

The distinction between low voltage motors, medium voltage motors, and high voltage motors is crucial in selecting the right motor for your application. Low voltage motors are often the go-to choice for applications requiring safety, reliability, and ease of use, such as in small machinery or residential applications. In contrast, medium voltage motors strike a balance between power and efficiency, making them ideal for industrial applications where both performance and energy usage are concerns. 

High voltage motors stand out in scenarios demanding high power and efficiency over long distances or in large installations. These motors are preferred in industries like mining, power generation, and water treatment facilities, where their ability to operate efficiently under harsh conditions is a significant advantage. 

High voltage vs Low voltage: 

• High voltage vs medium voltage motors are capable of delivering more power efficiently over longer distances, making them suitable for heavy industrial applications, whereas medium voltage motors are preferred for safer, less intensive applications where a high power is still needed. 
• Medium voltage vs low voltage: Low voltage motors are best for applications with minimal space and lower power requirements, while medium voltage motors offer a middle ground with better efficiency and power for industrial applications without the extensive infrastructure high voltage systems require. 

Choosing the right voltage for your needs

Selecting the correct voltage for an electric motor involves several considerations, including application requirements, energy efficiency, and operational cost. Here are some aspects to consider: 

• Application Requirements: Understand the power and performance needs of your application. High voltage motors might be overkill for light applications, whereas low voltage motors may not suffice for industrial needs. 
• Energy Efficiency: Higher voltage motors often provide better efficiency at higher power levels, important for reducing operational costs in energy-intensive industries. It may also be useful to consider the difference between IE1, IE2, IE3, and IE4 when selecting an electric motor. 
• Installation and Maintenance: Consider the complexity of installation and maintenance. Low and medium voltage systems might offer simpler, more cost-effective solutions. 
• Safety and Regulations: Ensure compliance with local safety standards and regulations, which may dictate the use of certain voltage levels. 
• Cost: While initial costs might be higher for high voltage motors and high efficiency motors such as IE4, the long-term savings on energy can offset these expenses for some applications. 

Choosing the right motor voltage is critical for optimising performance, efficiency, and cost-effectiveness. At Hoyer, our expertise and broad product range ensure that we can match the right motor to your specific needs, supporting your operations with reliable, energy-efficient solutions. 

For more information, please visit customized high voltage motor.

Wattage is wattage--the result in the motor should be identical, since you are talking about battery voltage and current.

Controller sees battery voltage and current.

Motor sees phase voltage and current.

It depends more on how you have the controller setup (particularly for programmable brushless controllers) than what voltage you run.


The main difference between the two is the size (and weight) of the supply wires needed between battery adn controller--hgiher currents will need much larger wires to keep resistance losses low.


the other difference is that if you already ahve a motor that could do either voltage at that power level, is that you run it at a much higher RPM for the higher voltage, so to get the same wheel speed you have to gear it down, vs a lower voltage with higher currents, at a lower RPM, where you might not have to gear it down at all, dpending on your sytem and requirements.

Since the gearing down makes it a little less efficient, there is some loss form doing the higher RPM...but it can make a system more efficient by not having some of the resistive losses int eh cable, the losses in the controller from heat at higher currents, etc.

if you work it out it is possible the losses in either case could be the same. I'm not a math guy, so you'd have to look up the numbers for your particular case and work them out. As a general rule, particularly applicable to direct drive motors, a direct drive motor can do higher and higher wattages where those wattages are derived more from the factor of voltage than from the factor of amperage.

This line of thinking underlines a general philosophy which holds that it is better to acquire the required wattage by using high voltages and low amperages. Hence the expression, "Volt up, Gear Down" {ie go for high voltage in a small wheel build eg 24", 20"}

Most DD motors can handle the 72v. Not all of them have a winding, or a lacing, or a wiring, that is 60/70/80 Amp friendly.

Example: When I was a noob, I bought a direct-drive motor off ebay. Here are its characteristics:

1. 8*8 Winding. Excellent. Won't need high amps, can handle all the voltage you fling at it, within reason.

2. 26" wheel build. Not good for high draw applications.

3. Long, skinny phase wires. Again, forget about high amps.

What was the best scenario for that motor? Run it at 72v 30A in a 26" wheel, or re-lace it into a 20" rim, rewire it with some 14G wires, and run it at 60amps for some fun.

There are many matters to consider. Terrain. Top speed. Size of the finished wheel. Riding style. Weight of the individual. All of these will dictate how your setup should be, or how well your existing setup will perform.

If you have an X in a 20" rim, then do what you please. Pump in all the amps you want. If you have an X in a 28" wheel, then better to use higher voltage, and much much lower amps.

However, the matter becomes complicated once the user moves beyond the 100v mark, where issues of reliability and safety, not stemming from amperage, begin to present themselves irrespective of the above factors. This is not to say that the issues mentioned above will disappear, but that new problems will present themselves anyway.

Specifically, the matter of controller-reliability, efficiency etc. Moving from Mosfets to Mosfets presents its own issues.

With geared motors, most of them "dislike" both voltages and amperages which go beyond 50 units.

Running MAC motors at 72v is asking for trouble, whereas the same voltage would be nothing to an X5 or a 9C.

I read here on this forum that 55v 50A for some of the original BMC geared motors was pushing the boundaries.

Inquisitor said: If there are two motors putting out a given wattage. One gets there with high voltage (say 120V/10Amps) and the other with high current (12V/100Amps) what are the ramifications for use in an EV project? I'm sure it can be very complicated (after struggling through some of the threads I've read), but I'm looking for that 90 percentile type generalities like are in the "PM Motor theory - formulae etc."

It gets more complicated when you take into account things further up the chain but for the motor itself it doesn't make any difference (assuming they are wound to run at the same speed). If you have a steep hill to climb and the motor can take it then you will need to give it more amps, sure run higher voltage and a smaller rim is best but not always practical, a 20" rear wheel looks daft on a mountain bike imo, but maybe someday I'll be converted. Once someone makes a custom frame for 20" wheels, I'll be sticking to 26" wheels.

I use 60 volts and 80 amps into a conhismotor 1kw, I had to rewire the phase wires, it's defiantly a front wheel lifter and because I Love to take the bike to the woods I need the 80 amps to get me up the hills, sure It couldn't take 80 amps battery, or 110 phase for too long, but It's a great little motor so far.

So many things to consider, such as how fast you want to go and what hills you got and how fast you need or want to get up them.

For Electric car, then higher voltages would be necessary for faster speeds but for a 40 mph E-Bike then 60 volts gets me there pretty quickly with the little conhismotor at 85 amps battery and 110 phase.

The only point of higher voltages to me seems to be for those that run smaller wheels and need to get the speed they want, for instance, 100 volts into my motor in a 20" wheel might make it go 40-45 mph and accelerate and climb just as good on 40 amps, the difference being it would run a lot cooler and is always the better way to go if your bike can take a 20" wheel. When I build my first Ebike, I chose 28" wheel and 48V. It was good for the first time, and fast too, but then I tried a 18" wheel Ebike with the same voltage and the amps were actually less and it was more powerful, but slower of course. And that's why I chose a high voltage and low amp setup. I'm using a 108V 42A controller and a 104V 33Ah battery pack (117.6V when fully charged) with 20" wheels and damn, it's powerful and fast too. Even 10 amps can do insane torque, because it's already around W, because of the high voltage. To be honest, I'm afraid of high amps, I've burnt some wires before, because of the high amps, so I don't need to worry about it here, and the high voltage won't hurt the battery, but the high current does. On fully throttle, one cell will only provide 4,2A, because it's a 28S10P setup, so that's not much current. The voltage drop is only a few volts. Also the higher RPM is more efficient, the cooling is better too, so I don't know the reason why people stick to lower voltages and raise the amps. My 42A can provide around W, while a 72V system would need 55A and the lower the voltage the more amp is required and of course more cooling to the battery pack and for the wires (or just use thicker wires). For the latest post, I've build a custom 20" full suspension frame, so it's not a problem for me. And for this rim size, motorcycle tires also available, which are designed for faster speeds and they are thicker to be more puncture resistant. There are many factors to consider. Diameter of the wheel and the Kv of the motor are huge influences.

So let's consider a chain driven motor to a small rear wheel to allow both competitors to spin at high RPMs.

One motor has many turns of small diameter wire, so it is a slow winding which requires higher volts to spin at "X" RPMs. The second example has a few turns of fatter wire for a fast winding (but same copper mass) which will use lower volts to achieve "X" RPMs.

The Alta motorcycles use 355V at low amps, and the Zero motorcycles use about 105V at higher amps.

If they are both sized to run with the same total Watts, the Zero will have less inherent resistance in its motor, because the fatter wire has a much shorter length in its winding.

Higher volts requires more cells in series, but slightly fewer cells in parallel. Lower volts use fewer cells in series, and maybe more cells in parallel, depending on the size of the cell and it's C-Rate.

90 cells in series requires 90 channels on the BMS, and higher voltage components in the controller and charger are less efficient.

Zero uses 28S, so the BMS only needs 28 channels.

A recent curveball is field weakening to raise the top RPMs of a given motor. This means you can lower the volts of the fast winding motor even more, but of course, you would need to raise the amps to still get the same watts.