## Search found 2814 matches

Jan 10 2020 4:48pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

What I do not follow is predicting motor efficiency from impedance matching, nor BEMF dictating motor output. I was using the efficiency to demonstrate where maximum power is transferred, that is all. When you tell someone that an electric motor makes the most power when it's loaded to 50% efficien...
Jan 10 2020 12:33am
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

Have I missed something? This discussion is about theory, money is irrelevant. :) Before coming to any conclusions you need to have a solid understanding of the problem which needs to be solved and any limitations. It's difficult to make generalizations for application. There are usually multiple w...
Jan 09 2020 6:04pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

Punx0r, what conflict do you see in my example trying to show the relationship between KV and MPTT?
Jan 08 2020 12:28pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

Punx0r or anyone, could you write a quick explanation of how BEMF works from your understanding? Keep it simple, use an ideal motor (no loss) and treat it as an impedance. We have a miscommunication happening and I'm not quite sure where it's at. How does BEMF limit input power? Where do the voltage...
Jan 07 2020 5:42pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

The 5V of BEMF is caused by the RPM of the shaft which is performing work on something. That work requires power which it is receiving from the shaft. Power at the shaft is voltage times current. There is 15V of voltage headroom left to add more power to the motor. Nope, that’s still not clear. BEM...
Jan 07 2020 1:20pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

I'll be honest I find your post hard to follow and I'm not sure if it's because there are mistakes or if it's correct but I can’t understand it. Or maybe it’s right but for the wrong reasons. For example, maximum power transfer theorem is about matching load to source and is generally unrelated to ...
Jan 06 2020 2:43pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

BTW, I know my title was click-bait I just wanted to talk nerd with other nerds for a bit, test out the explanation of the relationship between KV and and Power.
Jan 06 2020 2:41pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

Unless I'm missing something, motor efficiency is being muddled up with impedance matching: Output wattage: 150A * 5V = 750W of output power We are inputting: 20V * 150A = 3000W of power to the motor. It is outputting: 5V * 150A = 750W of work. Efficiency is output/input: 750W/3000W = 25% efficient...
Jan 06 2020 2:01pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

But but but :confused: he stutters. @zombiess: BEMF is the voltage resisting the input voltage, not the voltage doing mechanical work.. In your calc it’s all backwards or the motor would output max power at max back emf.. that is at noload where efficiency is zero. If your calcs above would be corr...
Jan 06 2020 12:32pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

If you only have 1V of headroom over the BEMF, then how are you getting 20A into your 0.1 Ohm motor? Do you mean 18V BEMF? For 19V BEMF, I think you have 0W output power, 190W iron loss, 10W copper loss, and you are 0% efficient. What I'm trying to illustrate is that when the motor is run at 19V, w...
Dec 31 2019 3:29pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

One of the times I was talking to Luke, it sounded like one of the reasons he preferred a high Kv motor at half-throttle compared to a lower Kv motor of the same type and size at full throttle (with both resulting in the same speed)...is that the high Kv motor had thicker wire and less resistance. ...
Dec 31 2019 3:22pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Re: Why more KV = more power, the Maximum Power Transfer Theorem

Dauntless wrote:
Dec 31 2019 2:18pm
We're going to have lower performance with hubs, but what is the real story comparing it to a middrive? Should we really want a high gear ratio?
You design for your needs, there is no one size fits all solution as they are all constraint dependent.
Dec 31 2019 1:17pm
Forum: Motor Technology
Topic: Why more KV = more power, the Maximum Power Transfer Theorem
Replies: 51
Views: 2432

### Why more KV = more power, the Maximum Power Transfer Theorem

I wrote this up some time ago when I was trying to understand the Maximum Power Transfer Theorem in relationship to sizing a motor and choosing a KV for driving a propeller at high RPM and high load for several top speed quad copters I built. Some basic electronics knowledge is needed to  understand...
Dec 02 2019 7:33pm
Forum: Motor Technology
Topic: Cheap FOCer 2 (Open-source, Low-cost, VESC 6 based ESC) (Prototyped. Materials have arrived for a test batch)
Replies: 20
Views: 2537

### Re: Cheap FOCer 2 (Open-source, Low-cost, VESC 6 based ESC) (Prototyped. Ordering materials for a test batch)

Of course I won't be able to out China China. You can totally out China, China. Just take someones money, send them a defective product, or the wrong product, or even better an incorrect defective product! Then when they ask for a refund, tell them sorry, but you'll provide them credit on their nex...
Nov 30 2019 9:33am
Forum: Motor Technology
Topic: STSPIN devboard
Replies: 5
Views: 671

### Re: STSPIN devboard

TI's Instaspin on their C2000 chips is really nice, but the code bas a fairly steep learning curve when you start using your own hardware. FOC Sensorless startup has worked on every motor I tried with a little tuning.
Sep 19 2019 8:29pm
Forum: Motor Technology
Topic: 100A through a MOSFET? FLIR video
Replies: 1
Views: 402

### 100A through a MOSFET? FLIR video

This is part of a series of tests I ran to quantify some maximum parameters of various MOSFETs. The one in this video is an IRFP4568. Turns out my setup was able to handle a maximum of about 120W of dissipation. Not going to happen once an insulator is in place, I only managed 66A when it was instal...
Aug 28 2019 1:03am
Forum: Motor Technology
Topic: Hi power inverter for Nissan leaf motor. Dyno's 302.3hp p15
Replies: 577
Views: 99034

### Re: Hi power inverter for Nissan leaf motor. Dyno's 302.3hp p15

Any particular reason you want to run 17" rims vs 15 or 16"?
Aug 04 2019 11:56am
Forum: Motor Technology
Topic: MOSFET gate driver ringing causes
Replies: 5
Views: 572

### Re: MOSFET gate driver ringing causes

What about snubbers in this situation of ringing? I've had luck implementing snubbers in one of my low power controllers (mainly compensating for bad layout). Can snubbers scale up to high power stuff? There are high power setups using snubbers but it's best to design to avoid snubbers if you can (...
Aug 04 2019 11:30am
Forum: Motor Technology
Topic: MOSFET gate driver ringing causes
Replies: 5
Views: 572

### Re: MOSFET gate driver ringing causes

yes, additional capacitors on the DC bus rarely help. The PCB must originally be designed to accommodate all caps with low inductance. My observation was that the new low frequency (660kHz) is the oscillation between the big DC bus cap and the new 1uF, and the high freq (10MHz) is between the 1uF a...
Aug 01 2019 4:51pm
Forum: Motor Technology
Topic: BESC - beefed up VESC motor controller for high power ebikes
Replies: 141
Views: 18743

### Re: BESC - beefed up VESC motor controller for high power ebikes

From where do you see it is EMI sensitive, by the gate ringing? By your 475 and 575ns which transitions do you mean exactly, can you show on a waveform? From what you said, I thought you had an EMI compliance issue. The 475ns refers to the time it takes the D-S to switch from 10% to 90% of it's ran...
Aug 01 2019 4:47pm
Forum: Motor Technology
Topic: MOSFET gate driver ringing causes
Replies: 5
Views: 572

### MOSFET gate driver ringing causes

We have several designs going on in this forum so I'll share some troubleshooting tips which hopefully aid in the design/construction. There are many issues which crop up when paralleling devices, most of them tie back to layout issues and parasitic inductance. For more details on this topic I sugge...
Jul 31 2019 1:38pm
Forum: Motor Technology
Topic: BESC - beefed up VESC motor controller for high power ebikes
Replies: 141
Views: 18743

### Re: BESC - beefed up VESC motor controller for high power ebikes

That's some good info Peters. I too have seen that same oscillation on the miller plateau in some of my previous testing. The way I handled it was to add a larger Cgs cap as you mentioned, and it worked really well in my own application, but my application was not noise sensitive. It appears your ap...
Jul 30 2019 3:48pm
Forum: Motor Technology
Topic: BESC - beefed up VESC motor controller for high power ebikes
Replies: 141
Views: 18743

### Re: BESC - beefed up VESC motor controller for high power ebikes

I reckon there are several options: 1. gate driver with desat. This is the most robust protection. The ACPL-33x series is also a choice, functionally similar to ISO5452. I use ACPL-332 nowadays. The difficulty with both of them is that they require 15V power supply, but some FETs operate better at ...
Jul 30 2019 3:26pm
Forum: Motor Technology
Topic: BESC - beefed up VESC motor controller for high power ebikes
Replies: 141
Views: 18743

### Re: BESC - beefed up VESC motor controller for high power ebikes

Part you listed is obsolete. :confused: Here is the status of the part from ST micro, says it's still an active part https://www.st.com/en/power-management/td350e.html The reason I'm recommending this gate driver to you is not because it's a top of the line chip, it's because I've fully tested ever...
Jul 28 2019 10:07pm
Forum: Motor Technology
Topic: BESC - beefed up VESC motor controller for high power ebikes
Replies: 141
Views: 18743