No-Load Brake Hoist (Vg+) - Magnetek Impulse G+ series 4 Instruction Manual

No-Load Brake Hoist (VG+)

The No-Load Brake Hoist mode provides a start and stop sequence designed specifically for No-
Load Brake Hoists. This mode is enabled automatically when the Motion is set to NLB Hoist
(A01-03 = 2). This will also automatically set the Stopping Method to No-Load Brake (B03-03 = 6).
Start
The start sequence begins by building up torque in the motor to a predefined level within the C08-01
(Torque Compensation Time) timer. This level is determined by several factors which are defined
below. During the C08-02 time, the drive is monitoring current to motor. The current feedback
equation must be satisfied within the time set in C08-02 (IFB OK Time). If it is not, a BE2 (No-
Current) fault will be displayed on the keypad and the drive will stop outputting voltage to the motor.
The brake will remain closed.
Once the brake has been commanded to release, the drive output remains in Load Float for the
amount of time programmed into C08-04. During C08-04, the drive waits for the brake to completely
open and watches encoder feedback. If the amount of feedback is less than the setting in C08-05
(Roll Back Count), then the drive proceeds to the BE3 check. If it is not, a BE1 fault is displayed on
the keypad and the sequence stops. For the BE3 check, if the brake opened mechanically, then the
encoder feedback must be greater than or equal to the value programmed in C08-07 (BE3 Detect
Count) within the time set in C08-06 (BE3/Alt Torq Tim). If it is not, then a BE3 fault is displayed. By
the time the drive has completed the BE3 check, there should be a significant amount of motor shaft
movement and the start sequence is complete.
Stop
The stop sequence begins when the run command has been removed and the output frequency has
decelerated to zero. Once at zero speed, the motor maintains a Load Float position for the duration
of C08-10 (Load Float Time). During the Load Float time, run commands in either direction are
accepted and will begin accelerating immediately in the commanded direction, thereby skipping the
start sequence entirely. The Load Float Timer is reset after each new run command. Once the Load
Float Timer expires, the brake output command is removed (thereby closing the brake) and Load
Float is maintained for the time set in C08-11 (Brake Set Delay) to allow the brake to fully close.
Once the Brake Delay Time has expired, the BE6 check is executed. The BE6 check monitors
encoder feedback while the load is being transferred from the motor to the brake and compares it to
C08-13 (BE6 Max Count). The encoder feedback must not exceed the number of counts in C08-13
within the C08-12 (BE6 Detect Timer) time. If it does (meaning the load slipped through the brake), a
BE6 alarm is displayed on the keypad and the drive will reset its Load Float position and maintain its
new position. Run commands will still be accepted with the exception of a reduced speed in the up
direction set by C08-18 (BE6 Up Speed Limit) and the NLB stop sequence will begin again once the
run command had been removed.
Torque Proving
Factor 1: On the first run command after power up, or after any major fault which causes the stop
sequence to be skipped, the start sequence by default uses the value programmed in C08-16, the
Initial Brake Release torque.
Factor 2: Once the system has completed a successful start and stop, a new Brake Release Torque
value is used. This value is one that has been memorized and stored into memory during the stop
sequence. It is equivalent to the amount of torque required for the motor to hold the load on the hook
in Load Float with the brake released. Some benefits of stored 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.
IMPULSE®•G+ & VG+ Series 4 Instruction Manual – February 2017
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