Power Supply Requirements; Section Overview; Selecting A Power Supply - Intelligent Motion Systems IM805 Operating Instructions Manual

S e c t i o n 5
S e c t i o n O v e r v i e w
This section covers the power supply requirements of the IM805. Precise
wiring and connection details are to be found in Section 7: Interfacing
and Controlling the IM805. The following is covered by this section:
S e l e c t i n g a P o w e r S u p p l y
S e l e c t i n g a M o t o r S u p p l y ( + V )
Proper selection of a power supply to be used in a motion system is as
important as selecting the drive itself. When choosing a power supply for
a stepping motor driver, there are several performance issues that must be
addressed. An undersized power supply can lead to poor performance
and possibly even damage to your drive.
T h e P o w e r S u p p l y - M o t o r R e l a t i o n s h i p
Motor windings can basically be viewed as inductors. Winding resistance
and inductance result in an L/R time constant that resists the change in
current. To effectively manipulate the rate of charge, the voltage applied
is increased. When traveling at high speeds, there is less time between
steps to reach current. The point where the rate of commutation does not
allow the driver to reach full current is referred to as voltage mode. Ideally
you want to be in current mode, which is when the drive is achieving the
desired current between steps. Simply stated, a higher voltage will decrease
the time it takes to charge the coil and, therefore, will allow for higher
torque at higher speeds.
Another characteristic of all motors is back EMF. Back EMF is a source of
current that can push the output of a power supply beyond the maximum
operating voltage of the driver. As a result, damage to the stepper driver
could occur over a period of time.
T h e P o w e r S u p p l y - D r i v e r R e l a t i o n s h i p
The IM805 is very current efficient as far as the power supply is concerned.
Once the motor has charged one or both windings of the motor, all the
power supply has to do is replace losses in the system. The charged wind-
ing acts as an energy storage in that the current will recirculate within the
bridge and in and out of each phase reservoir. This results in a less than
expected current draw on the power supply.
Stepping motor drivers are designed with the intent that a user's power sup-
ply output will ramp up to greater than or equal to the minimum operating
voltage of the drive. The initial current surge is substantial and could damage
P o w e r S u p p l y R e q u i r e m e n t s
n

Selecting a Power Supply.

n
Recommended Wiring.
n
AC Line Filtering.
IM805 Operating Instructions Revision R032306 19