Installation manual

27
Operational Overview
Torque Limiting
The Torque Command is calculated as shown previously, but its value is limited by the Torque Limit parameter and the
current foldback function (see "Torque Limit" and "Current Foldback"). The result of this limiting function is Torque
Command Actual. This is the command that drives the Power Stage to generate current in the motor. The Torque Limit
Active output function is active whenever the Torque Command Actual is less than the Torque Command. This will be
true when motion is stopped due to a Travel Limit input function.
Torque Limit Function
The Torque Limit Enable input function allows an external controller to limit the Actual Torque Command to a lower
value. The Torque Limit parameter is active only when the Torque Limit Enable input function is active.
Where:
T
TL
= Total Torque Limit
P
MT
= Peak motor torque
P
DT
= Peak drive torque
R
FL
= RMS foldback limit (80 percent of continuous system torque rating)
S
FL
= Stall foldback limit (80 percent of drive stall current rating)
P
TL
= Programmable Torque Limit
The Torque Limit Enable input must be active to use P
TL
.
If the application requires that the Torque Limit be enabled at all times, the Torque Limit Enable input function may be
setup to be Always Active to avoid the use of an input line.
Velocity Limiting
The drive commanded velocity is limited to 112.5% of the motor’s maximum operating speed. Depending on AC supply
voltage, it may or may not be possible to get to the motor maximum operating speed.
Overspeed Velocity Parameter
Motor speed is continuously monitored against the Overspeed Velocity parameter whether the drive is enabled or not
and when the motor speed exceeds the limit, or Overspeed Velocity Limit, a fault is issued. The default value for
Overspeed Velocity Limit is 13000 RPM.
The drive has an internal overspeed velocity limit. This limit is the maximum of the Overspeed Velocity parameter and
150% of the motor maximum operating speed. For example, an NT-320 with 4000 RPM maximum speed the internal
limit is 6000 RPM.
The Overspeed fault will be activated when either one of these two conditions are met:
1. When the actual motor speed exceeds the Overspeed Velocity Limit parameter.
2. If the combination of command pulse frequency and Pulse Ratio can generate a motor command speed in
excess of the fixed limit of 13000 RPM. In Pulse mode operation and any Summation mode which uses Pulse
mode, the input pulse command frequency is monitored and this calculation is made. For example: with a
Pulse Ratio of 10 pulses per motor revolution, the first pulse received will cause an Overspeed fault even
before there is any motor motion.
In Motion Velocity
The In Motion Velocity parameter defaults to a value of 10 RPM. If the motor Velocity Feedback is above the In Motion
Velocity value, the In + Motion or In - Motion output function is active. When the motor velocity falls below one half of
the In Motion Velocity, the In + Motion or In - Motion output function is inactive.
The maximum value for In Motion Velocity is 100 RPM and is intended to be used to indicate “in motion” not “at speed”.
The In Motion Velocity detect is monitored every 400 µs so machine jitter and torque ripple could cause flicker in
this signal if the commanded velocity is near the In Motion Velocity parameter value.
lower) is (whichever P or S ,R ,P ,PT TLFLFLDTMT TL =