FR-A701 INSTRUCTION MANUAL (Applied) - Automation Systems ...

Special operation and frequency control(2) Selection of encoder feedback control (Pr. 367 )Speed feedback rangeSet value(Set command)Driven loadRegeneration load⋅When a value other than "9999" is set in Pr. 367 Speedfeedback range, encoder feedback control is valid.Using the set point (frequency at which stable speedoperation is performed) as reference, set the higher andlower setting range. Normally, set the frequencyconverted from the slip amount (r/min) of the rated motorspeed (rated load). If the setting is too large, responsebecomes slow.Example: Rated speed of a 4-pole motor is 1740r/min (60Hz)Slip Nsp = Synchronous speed - Rated speed Frequency equivalent to slip (fsp)= 1800 - 1740 = 60(r/min)Nsp × Number of poles 60 × 4fsp ==120 120= 2 (Hz)(3) Feedback gain (Pr. 368 )⋅ Set Pr. 368 Feedback gain when the rotation is unstable or response is slow.⋅ If the acceleration/deceleration time is long, feedback response becomes slower. In this case, increase the Pr. 368setting.⋅Pr. 368 SettingPr. 368 > 1(4) Overspeed detection (Pr. 285 )DescriptionAlthough the response becomes faster, overcurrent or unstable rotation is liable to occur.1 < Pr. 368 Although the response becomes slower, the motor rotation becomes stable.⋅ If (detection frequency) - (output frequency) > Pr. 285 under encoder feedback control, E.MB1 occurs and the inverteroutput is stopped to prevent malfunction when the accurate pulse signal from the encoder can not be detected.Overspeed is not detected when Pr. 285 = "9999".CAUTION⋅ The encoder should be coupled on the same axis with the motor shaft without any mechanical looseness with a speed ratio of1 to 1.⋅ During acceleration/deceleration, encoder feedback control is not performed to prevent unstable phenomenon such as hunting.⋅ Encoder feedback control is performed once output frequency has reached within [set speed] ± [speed feedback range].⋅ If the following conditions occur during encoder feedback control, the inverter operates at the frequency within [set speed] ±[speed feedback range] without coming to trip nor tracking the motor speed.⋅ The pulse signals are not received from the encoder due to a signal loss, etc.⋅ The accurate pulse signal from the encoder can not be detected due to induction noise, etc.⋅ The motor has been forcibly accelerated (regeneration) or decelerated (motor lock or the like) by large external force.⋅ For the motor with brake, use the RUN signal (inverter running) to open the brake. (The brake may not be opened if the FU(output frequency detection) signal is used.)⋅ Do not turn off the external power supply of the encoder during encoder feedback control. Encoder feedback control functionsabnormally.♦ Parameters referred to ♦Pr. 81 Number of motor poles Refer to page 131350