Elevator inverter plays what role in the elevator (b)

Frequency down (low), if the same power output, the current increases, but under certain conditions, the torque current is almost constant.
Using elevator inverter operation, with a corresponding increase in the acceleration of the motor frequency and voltage, the starting current is limited to 150% of rated current (according to different models, 125% -200%). Labor-frequency power directly when starting current of 6-7 times, therefore, will have an impact on the mechanical and electrical. With elevator inverter drive can smoothly start (start time becomes longer). Starting current of 1.2-1.5 times the rated current, starting torque of 70% -120% of the rated torque; For enhanced functionality with automatic torque converter, the starting torque of 100% or more, you can start with a full load .
Frequency drops voltage V is also proportional to the decline, the question has been answered four instructions. The ratio between V and F are considered characteristic of the motor determined in advance, usually in the controller memory means (ROM) in that there are several features that can switch or the dial to select.
Down completely when the frequency is reduced proportionally to the voltage, the impedance becomes smaller as the DC resistance constant, would result in a low torque is generated under a reduced tendency to. Therefore, given the low frequency V / F, the output voltage is increased to make some manner so as to obtain a starting torque, this compensation called enhanced start. Variety of methods can be used, a method of automatically select V / F mode or adjusting potentiometer and other methods.
In 6Hz still output power, but according to the temperature rise and motor starting torque of the size of the other conditions, the lowest frequency of use to take 6Hz, at which point the motor rated torque can be output without causing severe heat problems. Actual elevator inverter output frequency (starting frequency) based on models for the 0.5-3Hz.
Normally when not. Above 60Hz (50Hz or more modes also) voltage constant, a substantially constant power characteristics, require the same torque at high speed, we must pay attention to the choice of motor and elevator inverter capacity.
Motor means to be used for speed detection device (PG), the actual speed back to the control means controls, called "closed loop", without PG operation is called "open loop." Universal Converter, mostly open-loop mode, and some models can be use PG feedback option.
Open-loop, the elevator inverter even if the output for a given frequency, the motor with a load operation, the motor speed in the range of the rated slip (1% -5%) change. For applications requiring speed accuracy is relatively high, even if the load change also requires close to a given speed operation of the occasion, PG feedback function can be used with the drive (optional part).
With PG feedback function of the elevator inverter, the accuracy improves. But the speed depends on the accuracy of implant PG itself elevator inverter output frequency accuracy and resolution.