Dear all,
We have a tower crane using Yaskawa inverter varispeed G7 (110kw)to drive hoist motor (90kw - 380V - 50Hz -990rpm -165A). The capacity of crane 1s 25tons with 6 line cable, and 16 tons with 4 line cable. When we lift a load about 10 tons, it runs well, but with a load about 12 tons, when starting pull up, load pulls the hoist down.

I think starting torque may be small so I increase Motor rate current parmeter to 190A, so hoist can lift up load well. But I am not sure because starting current and stop current is very high (peak current at starting time about 360-380A, and stopping time is about 420A). How can I decrease peak current at starting/stopping time? Frequency for closing brake is 6Hz.

Thanks
Chungtq
[email protected]

 

I had the same problem. The minute the mechanical brake released the motor started to free wheel. I had to add a dynamic braking resistor to my frequence drive.

 

Dear Friend,

You increase the ramp up time to 5 second so that the starting current can be limited.

Satya,
Qatar Steel

 

Perhaps you just need to change the Voltage to frequency curve.
The drive probably came standard with a parabolic curve for pump/fan operation. I saw something similar the other day on a constant torque diaphragm pump. The current was off scale at slow speed. Increasing the voltage at the bottom end bought the current right down, I'm still trying to understand that.
Roy

 

- First, be sure than you choose de Open loop Vector Mode. If you selected V/f is posible a failure stop caused by a overcurrent or overload. V/f mode is not convenient for lifting, only for variable speed (blowers and pumps). Could lose torque at low frequencies under 15Hz

- The autotuning can help to increase de torque and low de current.

- Check de DC current braking at running and stop, usually should to be upper 80% in your industry . The time deppends of the aplication but if is too large can cause a overload fault. The unit braking unit and its resistor bank is only necesary if the G7 internal braking it is not enough. Ask with your Yaskawa dealer.

Tell me who do you resolve your problem