zombiess
10 MW
There are a lot of rumors surround these controllers so I decided to dispel some of them and post hard evidence in the form of oscilloscope videos demonstrating what the controller does in each throttle mode.
Test setup is one of my custom built EB224-AS-1 IRFB4115 24 FET controllers running an unloaded Cromotor V0 with a 16" moped tire. I have no real way to load the system down besides the brake and really didn't have enough free hands to do that kind of testing right now, so these are all unloaded tests, but the PWM that occurs will hold true no matter what the load. I'm sure as more current flows there will be some spikes and possibly ringing on the FETs but what I saw here was minimal. I originally wanted to do some of these tests because of some of the conversations that Arlo1 and I have had about overshoot, he was curious to see what happens on these controllers. Hopefully I caught some of the info for you buddy.
As for the other topics... On to the myths!
Myth 1: The controllers never get to 100% throttle and is always in PWM - 100% FALSE!
I have read many times on here that these controllers never go to 100% throttle. This is not true at all, if you program the controller for 100% throttle on one of the switch settings you will drop out of PWM mode and end up at full on for the commutation.
Myth 2: The controllers stay in PWM when programmed for 99% throttle which is good for low inductance motors - 100% True
I've read that running these controllers at 99% throttle vs 100% or higher will help them drive low inductance motors with less failures. This should be true, because when I program my controller for 99% throttle it will NEVER drop out of PWM. This is a good thing if you have a hard to drive motor.
Myth 3: The controllers advance the hall timing to increase the speed when programmed over 100% - False?
I know that there has been a lot of guessing how the Xie Chang controllers increase the speed of a motor when set to over 100% throttle such as 105% all the way up to 120%. Some say it advances timing, some say it changes the throttle input, etc. Watch the video and see for yourself. What occurs is the normal trapezoidal wave form ends up going into a square wave with a little bit of PWM and is extended by about 10% past it's normal commutation cycle. My best guess without measuring one of the other phases simultaneously is that the PWM seen in this mode over 100% throttle inversely coincides with what is happening on the other phases thus preventing two phases being on simultaneously. In other words, phase A is on with no PWM, but as it starts to overlap phase B, they add in PWM that is the opposite of the next phase. In other words, phase A overlapping PWM is high, phase B PWM is low. This allows the over all time power is applied to the motor to be extended by around 10% providing additional time the motor is under power by eliminating the trapezoidal part of the wave form. At least this is my best guess as to how it's operating. It's certainly strange and I'm no expert, so motor experts, please add your thoughts.
Here is the video (it's uploading right now, give it about an hour from this post and it should be available.
[youtube]3tIt_FMTa6I[/youtube]
Test setup is one of my custom built EB224-AS-1 IRFB4115 24 FET controllers running an unloaded Cromotor V0 with a 16" moped tire. I have no real way to load the system down besides the brake and really didn't have enough free hands to do that kind of testing right now, so these are all unloaded tests, but the PWM that occurs will hold true no matter what the load. I'm sure as more current flows there will be some spikes and possibly ringing on the FETs but what I saw here was minimal. I originally wanted to do some of these tests because of some of the conversations that Arlo1 and I have had about overshoot, he was curious to see what happens on these controllers. Hopefully I caught some of the info for you buddy.
As for the other topics... On to the myths!
Myth 1: The controllers never get to 100% throttle and is always in PWM - 100% FALSE!
I have read many times on here that these controllers never go to 100% throttle. This is not true at all, if you program the controller for 100% throttle on one of the switch settings you will drop out of PWM mode and end up at full on for the commutation.
Myth 2: The controllers stay in PWM when programmed for 99% throttle which is good for low inductance motors - 100% True
I've read that running these controllers at 99% throttle vs 100% or higher will help them drive low inductance motors with less failures. This should be true, because when I program my controller for 99% throttle it will NEVER drop out of PWM. This is a good thing if you have a hard to drive motor.
Myth 3: The controllers advance the hall timing to increase the speed when programmed over 100% - False?
I know that there has been a lot of guessing how the Xie Chang controllers increase the speed of a motor when set to over 100% throttle such as 105% all the way up to 120%. Some say it advances timing, some say it changes the throttle input, etc. Watch the video and see for yourself. What occurs is the normal trapezoidal wave form ends up going into a square wave with a little bit of PWM and is extended by about 10% past it's normal commutation cycle. My best guess without measuring one of the other phases simultaneously is that the PWM seen in this mode over 100% throttle inversely coincides with what is happening on the other phases thus preventing two phases being on simultaneously. In other words, phase A is on with no PWM, but as it starts to overlap phase B, they add in PWM that is the opposite of the next phase. In other words, phase A overlapping PWM is high, phase B PWM is low. This allows the over all time power is applied to the motor to be extended by around 10% providing additional time the motor is under power by eliminating the trapezoidal part of the wave form. At least this is my best guess as to how it's operating. It's certainly strange and I'm no expert, so motor experts, please add your thoughts.
Here is the video (it's uploading right now, give it about an hour from this post and it should be available.
[youtube]3tIt_FMTa6I[/youtube]