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Electric motors with no rare earths

renaultgroup.com

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Re: Electric motors with no rare earths

#181

Post by ipbrown »

sitharus wrote: post #64
xeonmc wrote: post #61

Earlier quoted context omitted.

What advantage do permanent magnets provide that it isn't the case that all motors are made without them?

A lack of wear components. A permanent magnet motor uses permanent magnets on the rotor, but an electrically excited synchronous motor has an electromagnet on the rotor. This requires a rotating electrical contact which has normally been made with slip rings and carbon brushes. These wear over time and need replacement. Most large electric generators are externally excited synchronous generators using carbon slip rin…

I am a little surprised that Renault is only claiming a drive cycle efficiency of 92% (unclear for which drive cycle). It is possible to design EESM with brushless high frequency rotating transformers and rectifiers for WLPT drive cycles with greater than 94% almost 95% efficiency.

Re: Electric motors with no rare earths

#183

Post by ipbrown »

alephnerd wrote: post #59
MrDrMcCoy wrote: post #58

It's a bummer they are not really available in the US.

EVs in the US and China tend to use PMSMs, though GM, Stellantis, the DoE, and the DoD are funding an EESM startup [0] [0] - https://nironmagnetics.com/

Niron is not developing an EESM. They are developing Iron Nitride permanent magnets. These magnets can be used in a variable flux permanent magnet synchronous machine (VFPMSM). Variable flux machines have some similar characteristics to EESMs in terms of their ability to change the field excitation, but they are fundamentally different than EESM in terms of how they do so. EESM change their field excitation and VFPMSMs change the magnetization state through stator current pulses. Their current/torque regulation control is also quite different.

There are other startup companies developing EESMs but not Niron to my knowledge.

Re: Electric motors with no rare earths

#184

Post by ipbrown »

gmac wrote: post #108
ipbrown wrote: post #35

Electrically excited synchronous machines (EESMs), also known as wound field synchronous machines (WFSMs) have a number of potential advantages and disadvantages compared to interior permanent magnet synchronous machines (IPMSMs). IPMSMs are the dominant motor topology currently in use for North American electric vehicles. Advantages: - Not subject to the price and supply chain volatility of rare earth permanent magn…

It’s interesting that EESMs can be more efficient at high/highway speeds, and it’s something I had read before. This seems to me to be a key advantage of EESMs, because when people worry about EV range, they worry mainly about range on long-distance, high-speed journeys. (I have a Renault EV and it’s excellent. Aside from the motor technology, it’s relatively light, has a heat pump as standard, and a good-sized batte…

EESMs generally are not great at city driving cycles compared to IPMSMs. They do really excel in field weakening at moderate torques.

Re: Electric motors with no rare earths

#185

Post by regularfry »

dmurray wrote: post #136
regularfry wrote: post #106

Earlier quoted context omitted.

If you had bought a 7 or 5 Series at that time, you would not have had that experience. The 2001 7 Series had something like a 25% roadside breakdown rate.

25% every journey, or 25% over the lifetime of the car? Neither seems really believable but I don't understand how else you would measure this.

25% of cars. It was... not good.

Re: Electric motors with no rare earths

#186

Post by cbolton »

RicoElectrico wrote: post #179
adrian_b wrote: post #120

Unfortunately, their Web page does not say a single word about the important problems of their motors. The electrically excited synchronous motors have been known forever, but they had not been used in EVs because of 2 disadvantages. The first is that traditional EESMs require brushes, i.e. sliding electrical contacts, which are worn out by friction, so such motors require frequent maintenance for changing the brushe…

> The second disadvantage is a lower efficiency than with permanent magnets, which cannot be improved so much as to match PM motors, because the electrical currents that circulate through the rotor windings must generate heat. The lower efficiency also makes cooling more difficult. Wouldn't the back EMF help here? In brushed DC motor it surely does, reducing losses way below what full voltage over winding resistance…

That just means lower net voltage => lower current => lower torque right? When you do need torque you need current and the losses that come with it.

Re: Electric motors with no rare earths

#187

Post by cesarb »

tlb wrote: post #125
fc417fc802 wrote: post #71

Earlier quoted context omitted.

Not just some, approximately all of them. It greatly complicates the logistics of a black start. † Of course that situation has additional complexity due to the need for substantial additional power in order for the various fuel supply systems to operate but I digress. † https://en.wikipedia.org/wiki/Black_start

Generator excitation is not the hard part of a black start. You have to run coal feeders, blowers, and water pumps for an hour before you can spin the generator. Then you get power instantly upon applying power to the field windings.

> You have to run coal feeders, blowers, and water pumps for an hour before you can spin the generator.

That's probably the reason most grid black start facilities in my country (Brazil) are hydroelectric dams, which need none of these.

Re: Electric motors with no rare earths

#189

Post by MisterTea »

adrian_b wrote: post #120

Unfortunately, their Web page does not say a single word about the important problems of their motors. The electrically excited synchronous motors have been known forever, but they had not been used in EVs because of 2 disadvantages. The first is that traditional EESMs require brushes, i.e. sliding electrical contacts, which are worn out by friction, so such motors require frequent maintenance for changing the brushe…

> so such motors require frequent maintenance for changing the brushes.

Define frequent. I maintain machinery with brushes so I have a decent idea of what life span should be depending on the environment. If the housing for the slip ring setup is well protected from dirt and the slip rings aren't cleaned by a cave man you can get a few years of life from the brushes.

Re: Electric motors with no rare earths

#190

Post by chipsa »

MisterTea wrote: post #189
adrian_b wrote: post #120

Unfortunately, their Web page does not say a single word about the important problems of their motors. The electrically excited synchronous motors have been known forever, but they had not been used in EVs because of 2 disadvantages. The first is that traditional EESMs require brushes, i.e. sliding electrical contacts, which are worn out by friction, so such motors require frequent maintenance for changing the brushe…

> so such motors require frequent maintenance for changing the brushes. Define frequent. I maintain machinery with brushes so I have a decent idea of what life span should be depending on the environment. If the housing for the slip ring setup is well protected from dirt and the slip rings aren't cleaned by a cave man you can get a few years of life from the brushes.

If the desired location for this is a car, then a few years of life that requires half disassembly of a motor isn’t going to work.
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