48V 5KW BLDC motor with hydraulic pump issues

[Ammarqs]

Hello members of the forum,

I am trying to connect a 5KW BLDC motor to a hydraulic pump rated at 3500 RPM. The problem I am facing is that the motor RPM is more than 4500 RPM which is not safe for the pump and might blow it up. My application on the other hand does not have a constant load so I cannot assume the RPM drop of the motor according to its LOAD. So this is how it works, initially the pump starts at low load and within a few seconds the pressure and load increases and once it reaches 2000 PSI, my reverse solenoid hits and my hydraulics move back to their original position. But doing all this, the motor RPM on low loads is very high and might blow up my pump very easily. I tried changing the motor RPM set point with the software but that is only effecting the motor when its on LOAD and nothing changes when the pump is on low load.

Is there anyway I could program the controller to run at 3500 RPM max on low loads and then the RPM might drop as it should according to the torque/load on it.? So in short, I don't need the 5000 RPM on the motor because that messes my pump up.

If anyone has any solutions for it, please do reply. Our company is trying to replace the AC induction motor with these motors for our applications and it would be great if we could come up with a solution for this. Cost effective as well as low powered. If anyone has any further questions please feel to ask them and I will be glad to reply back.

Looking forward for someone to come up with a viable solution. I just hope I don't have to design my own controller for this purpose and we could find a solution using the current controller from golden motors. Thank you.

Ammar Surti
+1-681-212-9752
ammar@hydrolec.net

[Bikemad]

Hi Ammar andto the forum.

You haven't mentioned which controller or what voltage you are using, so I will assume that you are using the VEC300 controller.

The VEC300 controller uses torque control rather than speed control and I can't see an easy way around you specific problem, other than reducing the voltage (if possible) to lower the maximum rpm, use a different controller, or use a reduction gear/pulley system to physically reduce the rpm available at the hydraulic pump.

The HPC300 square wave controller seems to have rpm control instead of torque control.

It might be worth emailing david at GM China to see if he can help.

Alan
 

[Ammarqs]

Yes my controller is the VEC-300. Working with 48VDC. I can reduce the voltage if required. But will it make a difference at the RPM. I understand that voltage is directly proportional to the RPM and if the voltage is high so will the RPM be. But with this controller, I cannot say much about it. If thats the case, I can drop the voltage to 24 VDC.

[Bikemad]

I don't know whether that controller will run on voltages as low as 24V, so you might want to check if the voltage settings will allow it.
The PI800 programming software shows a lowest allowable voltage of 30V on the 48V setting (although this figure might change when the VEC300 controller is connected).

If the controller will only run as low as 30V, then 36V may be the lowest usable standard battery configuration, but you would need to lower the "Low Voltage Protection Value(V)" and the "Low Battery Voltage Value(V)" as well.

Replacing the 48V supply with a 36V supply should reduce the maximum rpm by ~25%, which might just be low enough for your hydraulic pump if you're lucky.



Alan