Load Float (Clv); Motor Torque Proving (Clv) - Hitachi P1 Basic Instruction Manual

LOAD FLOAT (CLV)

Load float is term used in closed loop vector control where the VFD can hold a load at 0hz / 0 speed without the use of the motor
brake. This function is available when operating in closed loop mode (AA121 = 10) and will greatly increase the life of the motor brake
by only using it as a holding/parking brake and not a dynamic brake in normal operation. Load float also gives the operator time to
make rapid precise movements.
HOW IT WORKS – When the hoist is commanded to stop in a normal operation the hoist will decelerate to 0hz and start the load float
timer. The load float timer will reset if a directional command is given before the load float timer expires. Once the load float timer
expires the motor brake will set and all directional commands will be ignored, and the brake slip test will begin.
Function
Load Float Time
Note – The load float time can be increased but if extending the load float time to a large amount of time an external motor cooling
device may be required or damage to the motor can occur.

MOTOR TORQUE PROVING (CLV)

Motor toque proving is safety check feature that checks to make sure the motor can generate sufficient torque to current ratio before
releasing the motor brake. This is safety check feature is only available when operating in closed loop vector control only (AA121 =
10).
HOW IT WORKS – The motor torque proving test works by applying a calculated torque value to the motor at 0hz / 0 speed at the
beginning of each lift and verifies the motor achieves the calculated torque and current prior to releasing the motor brake. Upon
powering up, fault reset, and or E-stop condition the value is 100%, and after the first initial lift it will be calculated based off the last
suspended load at the end of the lift cycle. When the VFD detects the motor has generated sufficient torque within the allowed test
time the motor brake will be released and the VFD will accelerate to the set frequency command after the motor brake delay time has
expired. If the motor fails to generate sufficient torque within the allowed test time the VFD will trip with and E51 fault code.
IMPORTANT! – Disabling this feature is not recommended unless troubleshooting without a load. Disabling this safety check feature
with a load suspended may result in dropping of the load.
TROUBLESHOOTING E51 – If an E51 fault occurs check the motor brake air gap. If the motor is turning during the test the VFD will try
and compensate by lowing the output torque value to maintain the 0hz/0 speed command and result in a E51 fault. Also check to
make sure the motor connections are secure and making good connection.
Function
Motor Torque Proving Test
Motor Torque Proving Test Max Allow Time
Setting the motor torque proving test max allow time to a low value can result in E51 faults.
Parameters
UE-29
Parameters
UE-30
UE-32
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Value
250 (2.5 seconds)
Value
0 = Disabled
1 = Enabled
400 (4.0 seconds)