ANYHZ FST-820 Elevator VFD Closed-Loop Current Anomaly Fix | Field Case Study

Background

Symptom: 20 A Current & Motor Over-temperature in Closed-Loop Mode

Drive: ANYHZ FST-820-7R5T4, 7.5 kW

Motor: 380 V / 15.4 A / 50 Hz / 1 440 rpm induction with 1 024 ppr encoder

Problem: current 20 A, motor > 85 °C, random over-current (OC) and overload (OL2) faults

Root-Cause Investigation

1. PG 12 V supply—false 6 V reading due to worn meter probe; real value 11.9 V ✔

2. Encoder waveform—clean 0-5 V square, 50 % duty, no missing pulse ✔

3. Auto-tune status—keypad showed “TUNE DONE” but motor was still coupled to gearbox ✘

4. Re-tune motor completely unloaded → new stator & rotor parameters saved ✔

Solution & Best Practice for ANYHZ FST-820 Elevator Applications

Always release traction sheave or remove belt before rotating auto-tuning (F1-11 = 2)

Back-up FA & FP parameter blocks after successful tuning

Use calibrated multimeter & oscilloscope to avoid “phantom” hardware faults

Brief site electricians on the ANYHZ tuning wizard—one careless click can mask itself as hardware failure

Result & Data Log

Closed-loop current stable at 13 A (only +0.4 A vs. V/F)

Cabinet ΔT < 8 K

Zero nuisance trips recorded in 30-day continuous log

Take-aways

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