ElmoMC SimplIQ Software Manual - Manual (Page 197)

SimplIQ Software Manual Limits, Protections, Faults and Diagnosis
MAN-SIMSW (Ver. 1.4)
13-2
Command Description
ER[N] Tracking error exception limits for speed and position.
HL[N] Protection high limits for position and speed feedback.
IL[N] Input logic. Defines digital inputs as stop and limit switches.
LC Limit current indication that indicates whether peak limit is active.
LL[N] Protection low limits for position and speed feedback.
MF States reason for a motor automatic shutdown.
OL[N] Output logic. Programs digital outputs as brake activation or as drive
ready indication.
PL[N] Peak current limit.
PS Program status.
SR Status register. Gives SimplIQ drive status, including if motor is shut
down by exception or if a Stop switch has been hit.
VH[N] Command high limits for position and speed reference.
VL[N] Command low limits for position and speed reference.
Figure 13-1: Commands Relevant to Limits, Protection and Diagnosis
CANopen offers an additional protection level: emergency objects issued in cases
of errors or applied protections (refer to the Elmo CANopen Implementation Manual).
13.1 Current Limiting
The drive protects the motor from over-current using a two-stage method. The motor
maximum peak current (given by PL[1]) is available for the peak duration time (specified
by PL[2]), while for longer periods, the current is limited to its continuous limit (CL[1]).
The current limiting process is dynamic: If the current has been close to its continuous
limit, the time allowed for the peak current is reduced. This process is determined as
follows:
The absolute value of the measured motor current (in vector servo drives, this is
2 2
D Q
I I
+
) is applied to a first order low-pass filter. The state of the filter is compared
with two thresholds. When the state of the filter is higher than the upper threshold, the
continuous limit is activated. When the state of the filter is lower than the bottom
threshold, the peak limit is activated.
The time constant of the low-pass filter is
⎥⎦
⎤
⎢⎣
⎡ −
−
=
MC
CL
PL
] 1 [
1 log
] 2 [
τ
where MC is the maximum servo drive current.