Required Drive Features
The drive can control the rate of acceleration and deceleration of the motor and load. These features control the amount of time the drive takes to increase or decrease the output during speed control.
Requires: A drive with programmable times sufficient for the application.
Each application has specific requirements for I/O. Analog I/O is generally used to read process signals and output signals proportional to drive status. Analog I/O is generally Voltage (0-10V) or Current (0(4)-20mA). The type and number required by the application must match the drive.
Requires: A drive with sufficient number and type of analog I/O.
Digital I/O
Each application has specific requirements for I/O. Digital I/O is generally used to control the drive (Start, Stop, Jog, etc.) and annunciate the drive status.
Requires: A drive that offers sufficient I/O and needed flexibility to perform all required func¬tions.
Droop
Specifies the amount of base speed that the speed reference is reduced when at full load torque. Use the droop function to cause the motor speed to decrease when an increase in load occurs. This function is normally associated with master/follower application.
Requires: master/follower firmware must be specified.
Applications that require rapid deceleration or quick stops can regenerate energy back to the drive. A dynamic brake dissipates this energy through a resistor as heat.
Requires: A drive that has an internal DB chopper and connectable resistor or has an external DB kit.
Dynamic Response
High performance applications often demand nearly instant response to changes in speed or torque commands or input status changes. The higher the dynamic response, the more capable the drive is in meeting these demands.
Requires: A drive that meets the response demands.
Overload Torque
Applications may require varying degrees of overload capacity for starting, accelerating, or intermittent duty. This overload capacity must be supplied by the drive as current and by the motor as torque.
Requires: A drive that has sufficient overload capacity.
Power Loss Ride-Through
Applications that control a continuous process cannot afford to stop because of short power outages or dips. The process must continue to run through these outages, typically 2 to 3 cycles long.
Requires: A drive that has sufficient power loss ride-through capability.
Slip Compensation
A squirrel-cage motor slips under load. To compensate for this, the frequency can be increased as the motor torque increases.
Requires: A drive that provides adjustable slip compensation.
Speed Range (10:1)
All applications operate over a given speed range, defined as the ratio of maximum continuous speed to minimum continuous speed.
Requires: A drive that can produce the needed torque and speed torque regulation (accuracy) over the required speed range.
Torque Proving
Some applications, like cranes, hoists and elevators, use mechanical brakes to hold the motor and driven machinery stationary while the drive is stopped. Prior to the release of this brake, the drive senses adequate current supplied to the motor to prevent dropping the driven machinery when the mechanical brake is released.
Requires: A drive that provides torque proving.
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