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.
Applications often require a precise measurement of load speed. Typically, an encoder is mounted to the motor shaft and its signal is used to indicate shaft speed. The drive can then adjust its output to the desired condition. Closed loop offers the highest accuracy and performance.
Requires: A drive with feedback capability, either as standard or as a plug-in option card.
Applications that involve multiple drives or drives controlled by PLC or other supervisory device often require communications via a defined network.
Requires: A drive that has a standard or optional connection to the desired network.
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.
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.
High Maximum Frequency
Most applications operate at speeds at or below the motor rated speed (typically 1800 RPM (60Hz)) for the US and 1500 RPM (50Hz) elsewhere. Other applications such as high speed grinders and winders need to operate at much higher speeds, sometimes with special motors.
Requires: A drive that has a high enough maximum frequency to allow outputs high enough to achieve the needed motor speed.
Long Motor Cable Length
Motors are rated by the manufacturer for the voltage resistance of the insulation system. If this insulation system voltage is too low, voltage reflection from the drive could cause motor failure. This is particularly important if the motor is a long distance from the drive and if the motor is an older motor being retained for the application.
Requires: A drive that has the lowest dv/dt or long cable mode of operation.
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.
PID Loop
An internal function provides closed loop process control with proportional, integral and derivative (PID) control. The PID function reads an analog input to the drive and compares it to a desired setpoint. The PID loop adjusts the drive output frequency (and therefore the process) to make the input value equal the setpoint.
Requires: A drive with one or more internal PID loops to eliminate the need for external hardware.
Position Regulation
A feedback device on the motor or machine, typically an encoder or resolver, feeds position information to the drive. The drive compares this information to a desired setpoint and adjusts its output to place the load in the desired position.
Requires: A drive that offers this control method when positioning without a separate positioning controller is needed.
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.
Reconnect to a Spinning Motor (Flying Start)
Applications with significant inertia and low friction tend to coast when stop commands, power interruptions or fault conditions occur. Many of these application require that when the condition disappears, the load must be reconnected at the 'coasting' speed / direction and returned to normal operation.
Requires: A drive with spinning motor reconnect or 'flying' start.
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 (100:1)
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.
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