How to use DC Machine as a generator?

I'm using DC Machine block from SimPowerSystem toolbox in Simulink and I would like use it as generator mode. I use the speed as mechanical input and I don't know if this speed must be introduced positive or negative for using generator mode. In addition I don't understand the help and I am confuse about the sign of the output speed and output torque when DC machine is generator.

Can anyone help me?

Best

Sergio

Answer 1

[Muruganandham Subramanian]

Hi,

   Generator==> I/P(Mechanical)(i.e. Negative for DC machine e.g. (-1 N.m (Torque))--> O/P (Electrical).

 If you need more explanation for this. Check this link too...
http://www.mathworks.com/help/physmod/powersys/ref/dcmachine.html

[Sergio Fragoso]

Hi and thank you for this answer

I've checked the link and I've seen that I must to use negative sign torque if I work with generator mode but would I use negative sign speed if I've selected speed as input port?

[Muruganandham Subramanian]

I think no need of (-Ve) sign for speed..and if this answer is helpful accept the answer