What is the difference between inrunner and outrunner motors?
Simply said, inrunners have the spinning part on the inside. Outrunners spin on the outside. Inrunners are typically used in combination with gearboxes, at least for high-speed motors. Our larger machines however (diameters > 1,6m) are also inrunners and mainly applied for high torque - low rpm direct-drive applications such as wind turbines. For vehicles, inrunners have higher rpm, mostly combined with a gearbox, while outrunners are typically used for direct driven in-wheel applications. Outrunners are also very useful for aircraft and drone applications where the rotational speeds are generally lower, but the weight must be kept very low. Magnax can deliver both configurations.
Can the axial flux motors function as a generator too?
Yes, the Magnax machines can function as generator and motor. The machine can be used in 4-quadrants operation by using the 4-quadrant inverter of your choice. As a result, our large diameter machines are typically applied as lightweight generators for ie wind turbines. The smaller (high-speed) axial flux machines, function as e-vehicle motor combined with regenerative braking or similar purposes.
Can the motors be stacked in parallel?
Yes, the machine concept is designed to connect multiple motors or generators in parallel and as such, multiply the torque and power of the generator / electric motor. However, we will require a design change and redevelopment. Please contact us to discuss in more detail.
How much acoustic noise does the machine make?
When you look at electric motor applications today; most noise is generated by the gearbox, not the electric motor. The magnax machines have a negligible noise level.
Which permanent magnets are used in the Magnax Axial Flux Machines?
Magnax machines use neodymium magnets, but more than 50% less magnets than traditional permanent magnet motors/generators. Even after 25 years of use, there is no measurable demagnetisation on the magnets. Some customers are afraid that the supply of the magnets becomes more difficult in the future due to the Chinese monopoly on the mining of the rare earth materials used in Neodymium magnets. However, new mines have been opened after the rare earth crisis in 2011. The problem is not that the amount of RE materials is limited because our Earth has enormous quantities of these materials available. It was the shortage of mines and the fact that most of them were located in China that resulted in the crisis. Since then, many new mines have been opened worldwide, including in countries such as Russia, Brazil, Thailand, India, Canada. What’s more, significant improvements have been made recently for the production of magnet metals which are RE free, and they will be able to meet the specs of the current magnets. More information around this subject: https://www.magnax.com/magnax-blog/permanent-magnets-china
Does Magnax provide the controllers / inverters?
Our machines stay below 1500 Hz, which means that no exotic power electronics is required. Magnax machines are designed to work with off-the-shelf inverters. Our machines can be used in 4-quadrants operation by using the 4-quadrant inverter of your choice. The main requirement is that the inverter can handle permanent magnet motors.
Does Magnax provide Battery packs?
No, but we are open to collaborations with battery suppliers.
Can field weakening be used for Magnax Axial Flux Machines?
Yes, from an electrical point of view, our axial flux machine is similar to the radial flux machine which means that also the magnetic principles are the same. Therefore field weakening can be equally used for the Magnax axial flux machines.
Most Magnax high-speed motors are designed for +/-400V to +/-750V battery voltage. Can lower battery voltages be used too?
Yes, we can modify the windings and as such, reduce the voltage. This won't have much effect on the performance of the motor. However, decreasing the voltage results in an increase in current, so the inverter must be capable of coping with these higher currents.
Does Magnax include a temperature sensor in the motor?
Yes, there is a PT1000 temperature sensor integrated.
Mechanical & Thermal
Does Magnax deliver gearboxes too?
No, but Magnax motors can be combined or integrated with existing or new gearbox solutions on the market.
Can we integrate a gearbox system to provide even higher torque at lower rpm?
Yes, a (planetary) gearbox (single or multi-stage) can be combined with Magnax machines. This results in a very compact solution compared with traditional induction + gearbox systems while the efficiency remains very high.
How long can the motor run at maximum torque or power?
This varies from 5 to 20 seconds, depending on the (ambient) circumstances. The primary influence on the overloading time is the chosen cooling strategy. We can expect better overloading capacity when the motor/generator is water cooled than air cooled. Peak torque (overloading torque) is generally twice as high as the nominal (continuous) value at a given rpm.
Is the bearing of the machine strong enough to cope with heavy duty axial, radial and torque loads?
Yes. the bearing system can cope with significant forces. Please contact us for details.
What kind of cooling fluid, the Magnax axial flux motors use?
The motor itself needs a water/glycol mix for cooling (ie 6 - 8 liters/min at a temperature of 50-60°C for the 275 mm version). Expected pressure drop is about 0,15 bar. Efficiency tests are done at 50°C coolant temperature in normal ambient temperature conditions.
How are the motors sealed?
Yes, the closed versions of the Magnax yokeless axial flux motors are IP67.