Applied Motion RS-232 - Manual (Page 131)

131 920-0002 Rev. I
2/2013
Host Command Reference
LA - Lead Angle Max Value
Compatibility: Stepper drives (except STM)
See also:
EF, LS commands
Returns the maximum lead angle setting for use in the Stall Prevention algorithm (see EF command for details).
This value is reached at the speed set by the LS command.
Lead Angle is the angular measurement between the internal magnetic field and the motor’s rotor. If the lead
angle is too large, the magnetic attraction fades and the motor will stall. Too small of a value makes inefficient use
of the magnetic attraction and the motor will not produce its maximum torque.
Lead angle directly affects the magnetic forces acting on the rotor, and is thus directly related to the motor’s
torque. An ideal setting for Lead Angle is essential for maximizing the motor’s torque output. During motion, the
motor’s lead angle is constantly monitored and adjusted to keep it within a speed-dependent operational range
and allow the drive to maintain control of the motor even in the event of a disturbance. The maximum lead angle
(set by LA) is reached at the Lead Angle Speed specified by LS.
This value is measured in electrical degrees. There are four physical motor steps (4 * 1.8 degrees = 7.2 degrees)
per 360 degree electrical cycle.
The relationship between electrical degrees and motor rotational displacement is given as follows:
360 electrical degrees / 7.2 rotational degrees
50 electrical degrees / rotational degree
Alternatively, in terms of physical displacement,
1 rotational degree / 50 electrical degrees
0.02 rotational degrees / electrical degree
The maximum effective setting for LA is 180 electrical degrees. If at any point the motor’s lead angle exceeds this
value, a stall condition will occur.
NOTE: While it is worthwhile to understand the meaning of the Lead Angle setting, it is intended that the ST
Configurator software be used to configure this setting.
Command Details:
Structure LA{Parameter #1}
Type BUFFERED
Usage READ / WRITE
Non-Volatile YES
Register Access None
Parameter Details:
Parameter #1 Lead Angle Value
- units integer
- range 1 - 180 electrical degrees