Motor is consuming less than rated current and more than rated power
Please check the graph below.



The rated speed is where the black vertical line (rated operating point) crosses the blue line (speed). This graph only applies when working at the nominal voltage.  

So, when you applied 24Vdc and the motor speed is 400 RPM, while the rated speed is 3000 RPM, you are quite likely close to stalling the motor, so operating in the right lower corner, at, let's say, torque Q.
Looking at the yellow/orange line (output power) at this torque Q, you'll find your output power is very low.
Looking at the red line (current) at this torque Q, you'll find the corresponding current. It should be higher than the rated current. Note that the input power is the(fixed) 24V times this current.  

So, at 400 RPM your measured current should be higher than the rated currrent. Your findings seem to contradict each other. Please double-check your the RPM, the current.

Some numbers:
Using on purpose \$w\$ instead of \$ \omega\$ as the first is in RPM, the latter in rad/sec, but they are proportional  

\$ \tau_{rated} = 0.32 \text{ Nm}\$
\$ w_{no load} = 4000 \text{ RPM}\$
\$ w_{rated} = 3000 \text{ RPM}\$  

Extrapolation the (blue) speed line:
\$ k_{speed} = \frac {w_{rated} -w_{no load} }{\tau_{rated} - 0} \$

\$ \tau(w) = \big( w_{no load} - w \big) \frac{1}{k_{speed}} \$

So, stall torque (@ RPM = 0) = \$ \tau(0) = 1.28 \$ Nm
And at 400 RPM, the torque = \$ \tau(400) = 1.15 \$ Nm

Extrapolation the current (red) line:
You can do the same calculations regarding the current and find that
the current at 1.15 Nm equals to 24.4 A.

If your current curve is expressed in amps, then your findings and above calculations are close. 

With DC motors, current is proportional with torque, voltage is proportional to speed. So, when controlling the speed, the voltage is being regulated. As torque is related to current and not (directly) to voltage, voltage control hardly limits the torque.  

It is likely your motor is not driven on 24V but a slightly lower voltage. At a lower voltage, the (blue) speed line drops (towards the x-axis), so the torque corresponding to the 400 RPM is slightly lower. And that torque will calculate to the correct current.