Hello,
I'm building a vehicle with dual Joby JM1S-2TY motors and am thinking about the controller options. The two obvious candidates I know of are the new 75V, 300A VESC and the Mobipus 72200. They have some pros and cons and questions each, so I thought I'll query the collective brain regarding them and other possible options.
The known (to me) specs of one motor is:
- Winding 2t wye (which will result in a rather low inductance)
- Kv 160 RPM/V (and thus something like 0.060 Nm/A)
- 22 poles, 11 pole pairs
- Nominal bus voltage 45-55 V
- 6000 RPM nominal, 9000 RPM max
- 13 Nm nominal, 20 Nm max
- Mechanical shaft power 8.2 kW continuous, 12.6 kW peak
I haven't found any current specs for this motor/wind combo, but by dividing torque by the (calculated from the specified K_v) torque constant one would arrive at 220 phase amps nominal, 335 A peak. This way the voltage back-calculated from power would be low, around 40 V assuming an electrical-to-mechanical 0.9 efficiency. 0.9 efficiency seems reasonable (if not even conservative) for these motors. If one calculates current through estimated input electrical power divided by specified ~50 V bus voltage one would end up with around 180 phase amps nominal, 280 A peak. But for this to add up with the other specs the K_v constant would have to drop to around 135 RPM/V at full load. Is this reasonable? Expected?
I don't know the exact inductance either. I do have a nice big lab-grade HP 4274A LCR meter, but it's currently stowed away under about 500 kgs of other electronic measuring equipment as a consequence of moving my lab... so currently I can't measure the true inductance with any degree of confidence I would trust. However, toolman2 gives an inductance of a Joby JM1S with (to me) unknown winding as 28 uH. From the other specifications for that JM1S I would guess it's either a 3T wye or a 4T delta wind, and if I understand it correctly the inductance scales like the square root of the turns ratio (ignoring other effects on inductance). This would make my motors have around 20-23 uH inductance. Sounds reasonable?
The main requirement on the controller is obviously that it needs to be able to run the motor. This implies:
- Managing at least 70k ERPM, preferably a bit over 100k
- Being able to run ~20uH motors
- Phase current around 200-250 A cont, 300-350 A peak
- Voltage tolerance of at least around 75 V for me to feel safe. I will probably start running at 12s and perhaps move up to 18s in the future
- Torque control throttle
- Buying something off the shelf. No PCB/electronics designing/building for me. I love doing such things and do it for a living, but that's not the focus for this project.
Nice-to-have features:
- Some kind of dual drive functionality
- Possibility to modify settings/firmware without external assistance
- Configurable and adjustable regen. Possibility to integrate some kind of brake chopper control/interface would be even better
- Possibility to read out all kind of stuff to a custom dashboard
- CAN, RS-485 or similar rugged/industrial/automotive interface with interface specs available
- Robust and reliable
- Efficient
- Small
- Cheap
The two good controller candidates I know of are the 75 V, 300 A VESC and the Mobipus 72200 or perhaps the next size up Mobipus.
Pros for 75/300 VESC:
+ Appropriate current and voltage rating
+ Known to handle high ERPMs
+ Known to handle low inductance
+ Very small
+ Reasonably good thermal interface
+ Rather open. Being able to dig around in and possibly modify the firmware is a huge plus to me.
+ Ben Vedder. Does amazing work and I would like to support him.
+ Potentially very good support
+ The low power VESCs have quite an user base and forum presence
+ Available in Europe
Cons for 75/300 VESC:
- Not quite on the market yet
- Not field proven
- Not as environmentally protected as Mobipus
- Expensive compared to Mobipus, even with the pre-order deal
- Delivery times for the preorders are highly uncertain with the VESC4 and 6 history in mind
- Potentially rather hard-to-reach support
- Supplier without extensive industry experience
Pros for Mobipus 72200:
+ Appropriate current and voltage rating
+ Smallish, but way bigger than VESC
+ Reasonably good thermal interface
+ Seems to be very rugged, fully potted and sealed
+ There seem to be some kind of communications bus interface
+ Cheaper than VESC
+ Field proven, I think(?)
+ Supplier with extensive industry experience (it seems)
+ Shenta. Does amazing work and I would like to support him.
+ samD. Seems to be helpful, communicative and active here on ES
+ Might be possible to get commercial pro support to get up and running
Cons for Mobipus 72200:
- Unclear whether it can do enough ERPMs for me
- Unclear whether it works with RC-style low inductances
- Not available locally in Sweden or in Europe
- A bit unclear what settings I will be able to manipulate without supplier support
- Support might be hard to reach
- Support might be expensive, if at all available
- Not open source firmware
- Control interface specifications are unknown to me, which means at least semi-hard to find on the internet
- No significant online user community/forums
Currently I tend to lean towards the Mobipus, even if I really like the VESC controller, the VESC project and Ben Vedder. I need to straighten out the ERPM and inductance questions regarding the Mobipus, though. @Mobipus official and @samD, do you know the max ERPM and min inductance?
@Trampa/Frank or even Benjamin, if you happen to read this: If I can get a good deal on two 75/300 VESCs I can lend you a Joby JM1S-2TY to test with! =)
And everyone else, any comments? Other suggestions for controllers?
I'm building a vehicle with dual Joby JM1S-2TY motors and am thinking about the controller options. The two obvious candidates I know of are the new 75V, 300A VESC and the Mobipus 72200. They have some pros and cons and questions each, so I thought I'll query the collective brain regarding them and other possible options.
The known (to me) specs of one motor is:
- Winding 2t wye (which will result in a rather low inductance)
- Kv 160 RPM/V (and thus something like 0.060 Nm/A)
- 22 poles, 11 pole pairs
- Nominal bus voltage 45-55 V
- 6000 RPM nominal, 9000 RPM max
- 13 Nm nominal, 20 Nm max
- Mechanical shaft power 8.2 kW continuous, 12.6 kW peak
I haven't found any current specs for this motor/wind combo, but by dividing torque by the (calculated from the specified K_v) torque constant one would arrive at 220 phase amps nominal, 335 A peak. This way the voltage back-calculated from power would be low, around 40 V assuming an electrical-to-mechanical 0.9 efficiency. 0.9 efficiency seems reasonable (if not even conservative) for these motors. If one calculates current through estimated input electrical power divided by specified ~50 V bus voltage one would end up with around 180 phase amps nominal, 280 A peak. But for this to add up with the other specs the K_v constant would have to drop to around 135 RPM/V at full load. Is this reasonable? Expected?
I don't know the exact inductance either. I do have a nice big lab-grade HP 4274A LCR meter, but it's currently stowed away under about 500 kgs of other electronic measuring equipment as a consequence of moving my lab... so currently I can't measure the true inductance with any degree of confidence I would trust. However, toolman2 gives an inductance of a Joby JM1S with (to me) unknown winding as 28 uH. From the other specifications for that JM1S I would guess it's either a 3T wye or a 4T delta wind, and if I understand it correctly the inductance scales like the square root of the turns ratio (ignoring other effects on inductance). This would make my motors have around 20-23 uH inductance. Sounds reasonable?
The main requirement on the controller is obviously that it needs to be able to run the motor. This implies:
- Managing at least 70k ERPM, preferably a bit over 100k
- Being able to run ~20uH motors
- Phase current around 200-250 A cont, 300-350 A peak
- Voltage tolerance of at least around 75 V for me to feel safe. I will probably start running at 12s and perhaps move up to 18s in the future
- Torque control throttle
- Buying something off the shelf. No PCB/electronics designing/building for me. I love doing such things and do it for a living, but that's not the focus for this project.
Nice-to-have features:
- Some kind of dual drive functionality
- Possibility to modify settings/firmware without external assistance
- Configurable and adjustable regen. Possibility to integrate some kind of brake chopper control/interface would be even better
- Possibility to read out all kind of stuff to a custom dashboard
- CAN, RS-485 or similar rugged/industrial/automotive interface with interface specs available
- Robust and reliable
- Efficient
- Small
- Cheap
The two good controller candidates I know of are the 75 V, 300 A VESC and the Mobipus 72200 or perhaps the next size up Mobipus.
Pros for 75/300 VESC:
+ Appropriate current and voltage rating
+ Known to handle high ERPMs
+ Known to handle low inductance
+ Very small
+ Reasonably good thermal interface
+ Rather open. Being able to dig around in and possibly modify the firmware is a huge plus to me.
+ Ben Vedder. Does amazing work and I would like to support him.
+ Potentially very good support
+ The low power VESCs have quite an user base and forum presence
+ Available in Europe
Cons for 75/300 VESC:
- Not quite on the market yet
- Not field proven
- Not as environmentally protected as Mobipus
- Expensive compared to Mobipus, even with the pre-order deal
- Delivery times for the preorders are highly uncertain with the VESC4 and 6 history in mind
- Potentially rather hard-to-reach support
- Supplier without extensive industry experience
Pros for Mobipus 72200:
+ Appropriate current and voltage rating
+ Smallish, but way bigger than VESC
+ Reasonably good thermal interface
+ Seems to be very rugged, fully potted and sealed
+ There seem to be some kind of communications bus interface
+ Cheaper than VESC
+ Field proven, I think(?)
+ Supplier with extensive industry experience (it seems)
+ Shenta. Does amazing work and I would like to support him.
+ samD. Seems to be helpful, communicative and active here on ES
+ Might be possible to get commercial pro support to get up and running
Cons for Mobipus 72200:
- Unclear whether it can do enough ERPMs for me
- Unclear whether it works with RC-style low inductances
- Not available locally in Sweden or in Europe
- A bit unclear what settings I will be able to manipulate without supplier support
- Support might be hard to reach
- Support might be expensive, if at all available
- Not open source firmware
- Control interface specifications are unknown to me, which means at least semi-hard to find on the internet
- No significant online user community/forums
Currently I tend to lean towards the Mobipus, even if I really like the VESC controller, the VESC project and Ben Vedder. I need to straighten out the ERPM and inductance questions regarding the Mobipus, though. @Mobipus official and @samD, do you know the max ERPM and min inductance?
@Trampa/Frank or even Benjamin, if you happen to read this: If I can get a good deal on two 75/300 VESCs I can lend you a Joby JM1S-2TY to test with! =)
And everyone else, any comments? Other suggestions for controllers?