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Altivar 312 Variable Speed Drives - Page 17 Introduction


Altivar 312

variable speed drives




Brake control This function is used to manage control of an electromagnetic brake in synchronization with starting and stopping the motor to avoid jolts and speed detected errors. The brake control sequence is managed by the drive. Adjustable values for releasing the brake: current threshold and time delay Adjustable values for engaging the brake: frequency threshold and time delay Enabled by: relay logic output R2 or logic output AOC assigned to brake control. This function is suitable for material handling applications with movements equipped with electromagnetic brakes (hoisting) and machines requiring holding brake control (unbalanced machines). Principle: Vertical hoisting movement: Maintains motor torque in an upward direction when the brake is being released and engaged, in order to hold the load and start smoothly as soon as the brake is released. Horizontal hoisting movement: Synchronizes brake release with the build-up of torque during starting and brake engage at zero speed on stopping, to prevent jolting. The recommended brake control settings for vertical hoisting applications are as follows (for horizontal hoisting applications, set the current threshold to zero): Brake release current: Set the brake release current to the nominal current indicated on the motor. If, during testing, the torque is insufficient, increase the brake release current (the maximum value is imposed by the drive). Acceleration time: For hoisting applications it is advisable to set the acceleration ramps to more than 0.5 seconds. Ensure that the drive does not change to current limiting. The same recommendation applies for deceleration. Note: For a hoisting movement, a braking resistor should be used. Ensure that the selected settings and configurations will not result in dropping or loss of control of the load being lifted. Brake release time delay t1: Adjust according to the type of brake. It is the time required for the mechanical brake to release. Brake engage frequency: Set to twice the nominal slip, then adjust according to the result. Brake engage time delay t2: Adjust according to the type of brake. It is the time required for the mechanical brake to engage. Limit switch management This function is used to manage the operation of one or two limit switches (with 1 or 2 operating directions). Each limit (forward, reverse) is associated with a logic input. The type of stop that occurs on detection of a limit is configurable as normal, freewheel or fast stop. Following a stop, the motor is permitted to restart in the opposite direction only. Monitoring The following data can be displayed: Frequency reference Internal PI reference Frequency reference (absolute value) Output frequency applied to the motor (value signed in two's complement) Output frequency in customer units Current in the motor Motor power: 100% = nominal power Line voltage Motor thermal state: 100%: nominal thermal state, 118%: motor overload threshold Drive thermal state: 100%: nominal thermal state, 118%: drive overload threshold Motor torque: 100% = nominal torque Last detected fault Operating time Auto-tuning status Configuration and state of logic inputs Configuration of analog inputs

0 1 0 1 0 Speed reference t Accessible settings: t1: brake release time delay t2: brake engage time delay Relay or logic output Motor current t Brake release current Speed reference Brake engage frequency LI forward or reverse T t1 t2 State of brake Engaged Released Engaged

Brake control


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