DC Variable Speed Drive aplication

[aquarius]

I have DC variable speed drive with 90V DC, 10Amp output. This drive can be controlled by 0-10V input signal. I have controller with temperature sensor which has 0-10V output.
I'm going to use controller and drive to regulate speed of 12V DC , 4Amp fans.
Please advise how is it possible to do this by using DC VSD and controller.
Thanks.

 

[Besoeker]

A 90V dc drive for 12V fans......
I don't know what kind of DC motors drive your fans.
Nor the application.

Assuming that the fans are for cooling and that the motor speed varies with applied voltage, the simple solution would be to have an analogue input reference, possibly 0-10V from a potentiometer, and 0-10V feedback from your temperature sensor.

 

[aquarius]

There are regular brushed 12V DC motors. My controller has temp. sensor and 0-10V out signal. Controller and VSD work perfect.
As far as I understand there is an option to connect 7 fans in series and let it go. Forgot to mention, it's possible to reduce output voltage to 48V DC (in this case 4 motors in series).
Is there any other option?

 

[gar]

090314-1902 EST

aquarius:

Assuming these are permanent magnet motors and all are the same model, then when connected in series the same current flows thru each motor. This means all will produce approximately the same torque, but not necessarily the same speed. In fact one motor or more could be stalled and thus force higher voltage on the non-stalled motors. This may not be a problem in a fan application, but you might want to run with some maximum current limit in the motor control.

Many motor controls, like Bodine, have a voltage input for speed control, but it is not isolated from the AC line and you can not connect from a source that is referenced to neutral, or ground without isolation.

Beyond these potential problems you may have stability problems.

.

 

[Besoeker]

090314-1902 EST
Assuming these are permanent magnet motors and all are the same model, then when connected in series the same current flows thru each motor. This means all will produce approximately the same torque, but not necessarily the same speed. In fact one motor or more could be stalled and thus force higher voltage on the non-stalled motors. This may not be a problem in a fan application, but you might want to run with some maximum current limit in the motor control.

I share your view on connecting the motors in series. Even with fans, there is the possibility of the load could differ for a number of reasons (bearing wear, dirt on the blades, even a physical obstruction for example).
We have sometimes run a couple in series but they were connected to the same mechanical load.

Beyond these potential problems you may have stability problems.

With a centrifugal load like a fan, there is a positive load v speed characteristic, so I don't think stability would be a great risk.