Magnetek IMPULSE VG+ Series 3, Instruction Manual, Page: 81 / 183

IMPULSE•VG+ Series 3 Instruction Manual – 07/25/05
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Torque Limit
IMPULSE•VG+ Series 3 dynamically controls the torque output of the motor at all times. The
Torque Limit Function limits the amount of motor torque on all four quardrants of vector control
operation:
• Forward Motoring
• Reverse Motoring
• Forward Regenerating
• Reverse Regenerating
No-Load Brake Start/Stop
The No-Load Brake Hoist mode provides a special start/stop sequence designed specifically for No-
Load Brake Hoists. This mode is enabled automatically when the Motion is set to NLB Hoist (A1-
03=2). This will also automatically set the Stopping Method to No-Load Brake (B3-03 = 6).
The NLB Sequence is comprised of a series of Timers and Counters that monitor certain feedback
devices. The sequence is divided into two parts, NLB Start and NLB Stop.
The NLB Start Sequence begins by building up torque in the motor to a predefined level within the
C8-01 (Torque Compensation Time) timer. This level is determined by several factors which are
defined below. During the C8-01 time, the drive is monitoring current to motor. The internal current
feedback equation must be satisfied within the time set in C8-02 (IFB OK Time). If it is not, a BE2
(No-Current) alarm will be displayed on the keypad and the drive will stop outputting voltage to the
motor. The brake will remain closed.
Factor 1: On the first run command after power up, or after any major fault which causes the NLB
Stop sequence to be skipped, the NLB Start sequence by default looks at the value programmed in
C8-16, the Initial Brake Release torque.
Factor 2: Once the system has completed a successful NLB Start and NLB Stop, a new value is used.
This value is one that has been memorized and stored into memory during the NLB Stop Sequence.
It is equivalent to the amount of torque required for the motor to hold the load that is on the hook in
Load Float with the brake released. Some benefits of memorized Load Float torque for the next
brake release are:
• Faster response to run commands when drive is in Base Block Status.
• Upon brake release, shaft rotation begins in the direction of the run command.
Parameter
Code
Display Function Range Initial Value
Access
Level
C7-01 Torq Limit Fwd FORWARD torque limit 0–300% 150 Adv
C7-02 Torq Limit Rev REVERSE torque limit 0–300% 150 Adv
C7-03 Torq Lmt Fwd Rgn Regenerative torque limit at
FORWARD 0–300% 180 Adv
C7-04 Torq Limit Rev Rgn Regenerative torque limit at
REVERSE 0–300% 180 Adv
C7-05 Torq Limit Gain Used when H1-01~H1-06 =
14 and MFI is on 0–2.55 1.25 Adv