ANYHZ FST-610 VFD for Rotary Kiln: 160 kW Inverter Handles 400 A Surge Without Tripping – 380 V Heavy-Duty Solution

Case Background

A local building materials company has a small 2.8 x 44m rotary kiln used for calcining active lime. The original system, driven by a 380V, 132kW three-phase asynchronous motor, a hydraulic coupler, and a reducer, suffered from long-standing issues such as severe startup shock, difficulty regulating speed, and high energy consumption. To address energy conservation and consumption reduction policies, the company decided to implement a frequency conversion upgrade.

Case Analysis

1. Direct starting with mains frequency caused an 800 A surge, resulting in frequent tripping of the distribution circuit breaker.
2. When the kiln coils formed, the current instantly surged to 400 A, causing the 132 kW standard inverter to frequently lock out in OL2 mode, resulting in sudden stops and detachment of the high-temperature kiln lining, leading to significant repair costs.
3. The hydraulic coupling had a narrow speed regulation range, making it impossible to achieve slow rotation to maintain the kiln lining or fast rotation to increase production. Power consumption remained high at 45 kWh per ton of ash.
4. Mechanical wear and starting shock caused pitting corrosion in the reducer gears and frequent coupling damage, resulting in annual repair costs exceeding 30,000 yuan.

Correctly Selecting an Inverter

The motor's rated current is 250A (132kW, 380V), but the actual load instantaneous current can reach 400A, 1.6 times the rated value! This means that if the inverter is selected based solely on the "132kW motor with a standard 250A rating," it will frequently overload and trip under abnormal operating conditions.

Therefore, ANYHZ engineers recommended the FST-610-160G/185PT4 (160kW, 380V) inverter, rated for 305A output current and a 150% overload capacity, capable of handling 457A for 60 seconds, to ensure no tripping.

Renovation Benefits

In the first month, a ringing current of 390A persisted for 8 seconds. The only sound heard on-site was the fan, and the kiln never stopped for a single second. Annual statistics showed a 60% reduction in startup shock, a 35 kWh reduction in power consumption per ton of ash, maintenance costs from 30,000 yuan to 8,000 yuan, and a 10% increase in continuous operation. The owner commented, "A higher-end inverter offers peace of mind and reduces kiln downtime."

Industry Implications

The 380V rotary kiln may appear low-powered, but it's a potent transient current hog. The key to selecting a model is this: "Measure the peak value first, then divide by the margin. The power rating is for reference only."
Raise the inverter's rated current to at least the peak value divided by 1.5. A little extra upfront investment will pay off later with fewer trips and kiln downtimes. The payoff is visible in the flames at the kiln mouth.