Maximising power from the HPM5000B

[Robb]

Hi,

I am trying to understand the differences between the voltage options for the HPM5000B.

The spec sheets show them all producing the same power, despite higher voltages. (but lower current obviously)

What are the practical differences here?

Ignoring overheating issues, what is the maximum power this motor can produce? and what components (driver/battery) are required?

[Bikemad]

Hi andto the forum Robb.

The motors are manufactured with different windings to specifically suit the stated battery voltages.

Looking at the test results, there appear to be different advantages for each of the motors:

The 48V appears to produce the highest rpm under no load condition.
The 72V appears to produce the most torque and the highest efficiency.
The 94V appears to produce the the highest rpm while producing ~10Nm of torque.

But there are also some disadvantages too:

The 48V motor has to run much slower to produce a similar torque to the other two motors.
The 96V motor appears to be the most inefficient motor.

If you are able to accomodate/afford a higher voltage battery pack, then I think that the 72V motor would be a better option than the 48V motor.

However, if your battery cells are unable to deliver the required current output, then the 96V motor might also be a better choice.

The 48V motor is probably ideal if you are restricted to a 48V battery which is capable of supplying the higher Amps it requires under load (or you don't require the maximum torque and power).

I don't know what the absolute maximum power output is for these motors, but I would expect it to be at least 10~12kW with a high current battery and suitable controller and the 96V motor. 

Alan
 

[Robb]

Hi Alan,

Thanks for the detailed response 

So its fair to say that the motors are wound specifically for a given voltage relative to efficiency. You could run the 48v on 96v, but it would just not be as efficient? (ignoring heat issues for the moment)

OK, so this is a little over simplified, but... If I used the  HPM5000B, with the VEC300 @ 72v (300A max current) and a battery capable of 300A burst, the theoretical burst power should be ~21KW (minus losses)?

[Bikemad]

If I used the  HPM5000B, with the VEC300 @ 72v (300A max current) and a battery capable of 300A burst, the theoretical burst power should be ~21KW (minus losses)?

Unfortunately that's not quite how it works, as the current figures stated relate to Phase current not battery current.

The Battery current is typically a lot less than the Phase current

According to the Motor Controller Guide the VEC300 controller won't be able to handle 300 Amps of battery current because it is only rated for 100A @ 72V:



100A x 72V = 7.2kW of input power not the power being produced at the spindle.
At 70% efficiency that would equate to a rated output of 5.04kW

The VEC500 controller would allow 150A @ 72V which is still only 7.56kW @ 70% efficiency.

Unfortunately, I can't find enough details on the VEC700 controller (700A Phase current) to see what it's battery current would be @ 72V.
It just says max. battery current 400A, but I assume that will be on 48v, so I'm guessing it will be ~300A or less at 72V (just over 15kW output @ 70% efficiency).

However, I expect these controllers will draw a lot more current during the programmed "boost" setting, but I don't know whether the boost current relates to Battery or Phase current, or what the maximum allowable input settings for this are.   

Alan
 

[Robb]

Thanks again for such a detailed reply Alan.

I found another site that is quoting the max battery current of the VEC700 @ 96V is 400A. seems a little high given the other controllers maximums. Its much bigger than the others though, 330mm x 225mm. Worth taking with a grain of salt.

Do you know if there are any trade offs using a high powered driver (ie Vec700) with this smaller motor? My reasoning is that buying a more capable controller at least lets me upgrade the motor at a later stage, instead of both components.

Regarding maximum phase current of the controllers -  is this higher than battery current because of the inductive load and the resultant voltage drop across the windings?

[Bikemad]

I found another site that is quoting the max battery current of the VEC700 @ 96V is 400A. seems a little high given the other controllers maximums. Its much bigger than the others though, 330mm x 225mm. Worth taking with a grain of salt.

It is all too easy to simply assume that the manufacturer's stated maximum voltage and maximum current occur simultaneously, but we know this is not the case. I suspect the seller has inadvertently misinterpreted the facts he has been given. 

I have also seen the VEC-700 controller advertised as 400A rated current and 700A peak, but does not specify that this is phase current and is dependant upon the voltage setting.

GM advertise the HPC700H square wave controller as 840A @ 48V:


If this was actual Battery Amps, at the absolute maximum voltage of "~140V" that this controller can accept, drawing 560A from the battery would extract over 78kW of power from the battery.
This seems to be very high for a controller with a rating of just 30kW and typically used with a 20kW motor.

Using a large current controller with a low current motor could easily cause overheating, but I am also not sure how well the torque controlled throttle would work with a much smaller motor. 

Phase current is typically higher than the battery current because it is being delivered in short intermittent pulses (sine waves) directly from the capacitors in the controller. The battery experiences the average current being supplied to the controller's capacitors, so it is typically lower than the peak current supplied to the windings on each of the undulating pulses.

At lower motor speeds, the voltage in the windings is continually being turned on and off several thousands of times every second (dependant upon the sine wave frequency), therefore the average voltage in the windings (the Phase voltage) is effectively a lot lower than the battery voltage.

If a battery is supplying 10A @ 72V it is using 720Watts of power, then this same amount of power is transferred into the windings but at a much lower average voltage.
If the maximum speed of the motor is 5000rpm @ 72V, it would need ~14.4V to maintain 1000rpm.
Presumably, if 720W of battery power was being drawn @ 1000rpm, the current in the phase windings (at an average of 14.4V) would be 50A, which is 5 times the battery current.

In reality, the battery voltage x battery current = motor voltage x motor current, but minus the losses due to inefficiencies within the controller and power/phase cables.

Alan
 

[Robb]

Coming back to this now...
 
After a bit more looking around, I am thinking of pairing the HPM5000 with a Sabvoton 72200, or 72150 @72v or 96v. 150A max battery current, or up to 200A if unlocked.

Provided cooling is kept in check, and the battery is up to the task, I should be able to get significantly more power out of the motor with this setup?