MGM esc programming problem

[Doug Smock]

@ Tomas, would it help if we are are sending you several 4/6-pole motors that we commonly use for you to validate the ESC parameters with? I would be willing to send you the ducted fan dyno I have with a TP4070 motor and even include the 40063 and 25063 I use.

-Tyler

Nice, thanks Tyler

[RaceMechaniX]

Have to disagree. I run Mostly LMT. We could drag race Terry. I have always said LMT were easier on controllers. Has anyone really done a torque comparison? You got the oval records because you guys in MI. Practice running ovals all the time. Your good at it.

Yes, I have compared both. The torque levels on LMT's are comparable to most 4-pole motors with similar sizes. However it takes more current to get the same torque. The LMT's are an ironless design meaning they do not have stator teeth. LMT's form the copper coils into loops and overmold with epoxy to set them in the correct positions. The benefit is more copper which can subsequently push more current. It does come as a penalty, but this is also one of the big reasons you can push a Lehner very hard for short periods.

Thermal limitations prevent the LMT's from sustaining the very high torque levels for long periods.

So LMT's will provide equal torque compared to a 4-pole, however they do it not as efficiently as a 4-pole.

The reason LMT's are easier on controllers is due to their near ideal waveform characteristics. i.e. the 2-pole produces a nice sinusoid waveform when the magnet assembly has a uniform field. 4-poles typically do not have as nice of a BMEF waveform which leads to inefficiencies.
Also, electrically speaking the LMT's run at half the speed of a 4-pole motor. Decreasing the switching events reduced the switching losses in the controller and hence reduces the heat from losses.
From the controllers perspective, a TP running at 25kRPM looks the same as an LMT running at 50kRPM.
This is another reason why it is hard to use 4 and 6 pole motors for high RPM set-ups like SAW's as the electrical switching frequency is high which increases losses.

[T.S.Davis]

Lehner's work just fine for oval racing,

I suppose but if you look at the records for both IMPBA and NAMBA you will find very few 2 pole motors setting records. There are zero 2 pole oval records in IMPBA. Only straight line records.

[RaceMechaniX]

I still hold 3 2-lap records with LMT motors in NAMBA and 1 in IMPBA (1/4 mile Q hydro). Looking through the non-SAW records I am the only person running LMT's.

I guess I have some more work to do.........

[photohoward1]

I wanted to say what Tyler said but he stated it so much more......intelligently?


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[Tomas_MGM-CONTROLLERS]

Thank you RaceMechaniX for detailed technical explanation.

It is correct the Lehner motor inrunners doesn't provide high torque right from the beginning during acceleration.
They need to achieve high rpm at first and then they provide high torque as well. These 2-pole motors will achieve high RPM quickly.
So these motors are the most efficient, when they achieve high rpm like most inrunners.

MGM CONTROLLERS ESCs can handle up to 250k RPM with 2 pole motors, 125k RPM with 4-pole motors, etc.
So there is enough potential to run multi-pole motors at high RPM.
Therefore MGM controllers won't get overheated because of achieving the limit of electrical switching frequency. The limit is high enough.

We still think there is no problem running motors with many poles with our ESCs.
The real problem is running the motor at higher voltage and higher load than they can really handle.

If you overload the motor by combination of related variables (high voltage, large propeller, heavy boat, quick throttle changes, aggressive parameter settings, raising temperature, etc.), then it will create high current peaks (phase currents).
Unfortunately, no available controller will handle that because currents will eventually become too extreme, even before achieving mechanical rpm limits of motor. This can also lead to overload and damage of your batteries.

There is difference between voltage, which a motor can handle without load and voltage, which a motor can really withstand under given load.

Yes, the motor can usually survive this overvoltage and mechanical overload by large propeller, etc., because it is more simple and sturdy component than speed controller. So the motor can be for example just demagnetised after some time.

In more extreme case high currents will cause temperature to raise too high, which can additionally damage insulation of motor windings or cables. And it will destroy the motor and consequently also the controller.
So yes, you can run your motor at the edge of its specifications and rating, but then you need to be prepared for possible consequences.

Somebody says that Lehner motors did not evolved enough over years compared to other manufacturers. There are improvements and development of course, but important is that these motors work as expected according to their specifications.

Some other manufacturers did evolve their motor specifications, but probably only on the paper. Otherwise we would not have to solve many issues caused by using too high voltage and mechanical overload.

It is good idea to provide us with motor or ducted fan, That would be really great. We can record history and obtain results regarding different motors from testing. This would also verify the specifications of motors.


In the end, I would not worry about using a 6-pole motor with our controllers. Even 20-pole motor like Lehner Torqstar can work well. Many customers are using these motors in surf boards, boats, airplanes, etc.
Everything is just a matter of right combination of components and settings.

[Fluid]

I really appreciate Tomas’ input here, and I have a few questions. Why can the (relatively) cheap Castle controllers handle these ‘high current peaks’ without shutting down or burning up? (Their big Achilles heel is getting wet.) And why do MGM controllers seem to log much higher peak current than Castles do with the same setups? Thanks!


.

[RandyatBBY]

I still hold 3 2-lap records with LMT motors in NAMBA and 1 in IMPBA (1/4 mile Q hydro). Looking through the non-SAW records I am the only person running LMT's.

I guess I have some more work to do.........

My 1971 Miss Budweiser runs a LMT 2030..... when I can find some one to run with.

To hit 70+MPH with a oval P Sport what motor and prop would you recommend?

[RaceMechaniX]

I really appreciate Tomas’ input here, and I have a few questions. Why can the (relatively) cheap Castle controllers handle these ‘high current peaks’ without shutting down or burning up? (Their big Achilles heel is getting wet.) And why do MGM controllers seem to log much higher peak current than Castles do with the same setups? Thanks!


.

Jay, Just to clarify the MGM's are likely logging the same DC currents as the Castles and this what most people look at. The current limiting in the MGM's is due to phase current limiting. The MGM controllers are either predicting or measuring the phase current and logging this data in addition to the DC current. The Castles can handle it because they are not protecting for it, nor do they report it in the logging. Castle's are only looking at the DC current for their watchdog mechanism and likely the temperature sensor. I do not believe Castle have implemented more elaborate watchdog mechanisms that predict FET temperatures with respect to time and current like MGM does. And this is why they fail catastrophically.

Phase currents are a lot more complex than DC input current. You can have very high phase currents and low DC input currents.

[RaceMechaniX]

My 1971 Miss Budweiser runs a LMT 2030..... when I can find some one to run with.
To hit 70+MPH with a oval P Sport what motor and prop would you recommend?

Randy, I assume you a have a typo for the 2030.

For P-sport, I run a Phil Thomas Stealth on 4S2P with a 1950/5 and a X440/3. It will run 72-74 although it is completely undriveable.

DSC_4735.jpg

[RaceMechaniX]

Thank you RaceMechaniX for detailed technical explanation.

It is correct the Lehner motor inrunners doesn't provide high torque right from the beginning during acceleration.
They need to achieve high rpm at first and then they provide high torque as well. These 2-pole motors will achieve high RPM quickly.
So these motors are the most efficient, when they achieve high rpm like most inrunners.

MGM CONTROLLERS ESCs can handle up to 250k RPM with 2 pole motors, 125k RPM with 4-pole motors, etc.
So there is enough potential to run multi-pole motors at high RPM.
Therefore MGM controllers won't get overheated because of achieving the limit of electrical switching frequency. The limit is high enough.

We still think there is no problem running motors with many poles with our ESCs.
The real problem is running the motor at higher voltage and higher load than they can really handle.

If you overload the motor by combination of related variables (high voltage, large propeller, heavy boat, quick throttle changes, aggressive parameter settings, raising temperature, etc.), then it will create high current peaks (phase currents).
Unfortunately, no available controller will handle that because currents will eventually become too extreme, even before achieving mechanical rpm limits of motor. This can also lead to overload and damage of your batteries.

There is difference between voltage, which a motor can handle without load and voltage, which a motor can really withstand under given load.

Yes, the motor can usually survive this overvoltage and mechanical overload by large propeller, etc., because it is more simple and sturdy component than speed controller. So the motor can be for example just demagnetised after some time.

In more extreme case high currents will cause temperature to raise too high, which can additionally damage insulation of motor windings or cables. And it will destroy the motor and consequently also the controller.
So yes, you can run your motor at the edge of its specifications and rating, but then you need to be prepared for possible consequences.

Somebody says that Lehner motors did not evolved enough over years compared to other manufacturers. There are improvements and development of course, but important is that these motors work as expected according to their specifications.

Some other manufacturers did evolve their motor specifications, but probably only on the paper. Otherwise we would not have to solve many issues caused by using too high voltage and mechanical overload.

It is good idea to provide us with motor or ducted fan, That would be really great. We can record history and obtain results regarding different motors from testing. This would also verify the specifications of motors.


In the end, I would not worry about using a 6-pole motor with our controllers. Even 20-pole motor like Lehner Torqstar can work well. Many customers are using these motors in surf boards, boats, airplanes, etc.
Everything is just a matter of right combination of components and settings.

Tomas,

I will coordinate with you to ship the set-up to you along with the motors.

Tyler

[T.S.Davis]

Phase currents are a lot more complex than DC input current. You can have very high phase currents and low DC input currents.

Doesn't really clarify what Jay is asking. For me at least it doesn't.

A known setup running on a 200 amp cheep speedo works where as it burns a 280 amp MGM into a crispy critter. How can this be? A bit less subtle than Jay's version but the question still stands.

How do the phase currents relate to the amp rating on the speed controllers? Some had for instance setups running on something as cheap and simple as a Seaking 180. They decided to step up to higher quality controller. So they opt for the 280 thinking nice cushion. Only to find it doesn't work at best and burns to a crisp at worst. Is the "rating" 280 amp phase current or or 280 amp DC input current?

If the rating is a DC input current then why when we read the the data log are we being given phase currents? It doesn't mean what we think it does. No other data logger does this. Castle, Swordfish, even the Eagle tree tells us phase current. If the log actually shows DC input current on the log to be over 1000amps........how is it possible that a cheesy Seaking 180 can run a setup that a high quality MGM rated for an additional 100 amps can not?

[jaike5]

MGM only plays well with A,B, motors. Does not play well with C,D,E,F,G motors. and over propping. The manufacturer must stipulate this, other wise your dropping 2k and still don't what motor this thing likes. That's what I'm getting out of all this great info put forth.
Cheers, Jay.

[RaceMechaniX]

Terry,

Castle has developed a very good control strategy for the TP/Neu motors likely as a result of the close relationship with Steve Neu. Recall that most of the Castle motor design was from a license agreement with Neu Motors. Similar story with MGM who is well paired with Lehner thanks to their good relationship. MGM is a large dealer of LMT motors and pairs their controllers with LMT motors for various applications like the Losi 5B conversion and the TorqueStar outrunner for planes.

MGM logs DC input current, Peak current and Pulse current. DC current is the average battery current, peak current is the current flowing through the phases and pulse current is the calculated peak current value. I found a current definition in the MGM manual:

MGM Current definition.jpg
Current table.jpg


Castle only logs DC input current. Castles are not using phase current as a watchdog safety to pull back the current (at least that I know of). Don't just look at the pop up graph MGM supplies, download the .csv file and open in excel to check all the data. There you will see DC current and AC phase current.

To try and answer why the two currents are different: AC phase current is what produces the torque in the motor and is mostly independent of RPM. DC current is proportional to the duty cycle you are asking for and the speed of the motor. If you maintain a certain torque in the motor, but increase speed the power (DC current) goes up. AC phase current generates the torque, but is often clipped as speed increases to reduce the DC current. Otherwise your power would go through the roof. This clipping point is often known as the knee point in a motor torque curve where the control strategy switches from constant torque to constant power.

They look like this: 1682147d214d1e617551359320d2ee56.jpg


At low duty cycles, you can have high peak phase currents, but low DC currents. At high duty cycles you can see both high DC and AC current.

The best answer I can give is the two companies use different PWM strategies and different free-wheeling controls. The MGM I believe is active free-wheeling and I know the Castle's are passive free-wheeling. Better explanation here: https://youtu.be/uqzOQGiwGnE The PWM strategies have a significant effect on phase currents as well as the losses in the board.
How many people have actually burned up an MGM controller? I know about burning up motors, but what about the actual controller? I believe this is pretty rare certainly compared to Castles and others. Castles Achilles heel is poor cooling and as many of use are aware they burn up if you can't cool them enough. Several of us have pushed Castles over 450A thanks to improved cooling.

Most data loggers are measuring DC current only. This includes the Castles, Eagle Tree's, SF's, etc. I don't believe MGM is physically measuring the phase currents on the hobby level controllers, but calculating it with the voltage drop across the FET's and the temperature of the FET's.


If you want to learn more have a look at this thread on Helifreak comparing YGE and the Castle Creations 160HV https://www.helifreak.com/showthread.php?t=443322

Here are two great youtube video's comparing the Castle 160HV and Kosmik200HV:

Full Throttle: https://youtu.be/z7jewAN1dTw

Partial throttle: https://youtu.be/AKN18ZTqoag

A FET's current rating is advertised as an AC current rating. The rating is typically made a 25C and under ideal cooling conditions. The current rating falls off quickly as the die temperature in the FET increases. Hence we need paralleling of FET's to achieve a more realistic under load rating.

There is no way every manufacture could say which motors don't work which is why you come to a forum to ask. All the manufactures can do is recommend good pairings which are known to work.

Final comment: All the amp ratings we see in the hobby business are BS. Just like the C ratings on batteries.

[T.S.Davis]

My take on these at this point is to run a Lehner for which they were designed or don't run them.

I don't know what to believe on any controller ratings to be honest.

The Seaking 180 Version 2 was a beast. Way under rated. Of ciurse they ruined it. The V3 was a POS.

The Mamba XLX with some decent cooling we yanked 330 amps from on the oval. That was the motor that burned my 280 to a crisp with less prop on it BTW. The log said I was pulling over 1000 amps. Sigh.

The MGM I tried to count in my head just now. Our club has or has had at least 10 of them now. One of them runs reliably. That one can't be adjusted in any way. So maybe $4000+ US worth of paper weights. Most of our guys refuse to put them in their boats. They won't finish.

Sorry to be so negative Tyler but when you take a leap of faith, endorse a product, and then realize you've led your guys down an expensive path it's very frustrating.