Problem of Inverter


Thread Starter

Wu Yiyan

Hello AUTOMATION, We want to tend for a project to upgrade the control system of a crane, we have some technical problems about inverter. Here are the questions: 1. There is 1 motor for lift, and the parameters are: Rate lift force: 2X250 KN Brake moment: 500 N.M Motor type: YZ200L-8 (Made in China) Motor rate power: 18.5 kW Motor rate rev: 697 rmp This motor is squirrel-cage motor. There are 4 motors for crane move on the railway, and the parameters are: Moving load: 14600 N Brake moment: 15 N.M Motor type: YPE-4-750Si (Made in China) Motor rate power: 0.75 kW Motor rate rev: 1380 rpm These 4 motors are wound motor. The power source is AC. 380 V, 50 Hz. We want use inverter for control of these 5 motors, how can I select the inverter for them? 2. For the economy reason, if I can use 1 inverter for the 4 moving motors? and how can I select the inverter? Or for the more economy way, if I can use only 1 inverter for these 5 motors? (Because there are some interlock between the lift and move, these 2 operate state can't work at the same time) And how can I select? 3. Are there any different of using inverter for wound motor and squirrel-cage motor? This project is an urgency, and it is holiday in China, so I ask you these question directly. It will be very helpful to answer me as soon as possible, thank you very much. -- Best regards, ZH mailto:[email protected]

Hakan Ozevin

For the lift motor, you have to use a dedicated VSD with 4-quad operation and special software for cranes. Standart VSD's will fail. You can try ABB ACS600 Cranedrive or Siemens Masterdrives with crane option. For the moving motors, you can use one VSD, but note that there will be no slip compensation, therefore the crane will not stop at the same place as its weight changes. However, this should not be a problem since nevertheless you must have a position sensor to detect the position of the crane. You can use a standart inverter for this purpose, but choose it from the nominal currents of the motors, not from the power (4 pieces of 0,75 kW motor draw more current than a single 3 kW motor). You can drive wounded motors from a VSD; just short circuit the secondary (rotor) windings. Hakan Ozevin

Robert R. Stephens Pennzoil Products

<< 3. Are there any different of using inverter for wound motor and squirrel-cage motor? >> I will take a shot at answering this question. Using a VFD(Inverter) with a wound rotor motor is probably not a good idea and probably wouldn't work since you are stepping rotor resistance into the circuit and the speed and torque is changing. The VFD would not react well. You could short out the resistance and run the wound rotor motor as a squirrel cage motor but you may not have enough torque available because a wound rotor motor with the resistance shorted acts like a type 'A' squirrel cage motor while the standard squirrel cage motor is a type 'B.' Type 'A' and type B are NEMA designations that pertain to the speed torque curve. Some other comments: It's best to use inverter rated motors with VFD's but not absolutely necessary. Generally, the life will be shorter if the motor is not inverter duty. It is probably not a good idea to use one inverter(VFD) with 4 motors. The drive wouldn't handle the switching well. It looks like you are talking about a 25 HP (lift) drive and 4, one HP rated drives. Good Luck. Rob Stephens
Give your local Control Techniques Rep / Distributor a call. We have applied the UniDrive in a similar crane application with great success.

Culver, George

For Crane Hoists it is important to utilize a flux-vector (field-oriented) variable frequency drive that has crane specific firmware. The two most important crane specific features are torque-proving and brake-proving both of which are essential to reduce the risk of dropping a load. For load holding and for micro positioning a shaft encoder on the motor is required to provide feedback to the drive. The wound rotor leads can be shorted and the motor will perform much like a squirrel cage motor powered by an inverter. Contact a vendor who has much experience applying drives to cranes since there are serious life safety issues involved. George Culver Senior Electrical Engineer Huntair Inc. (503) 403-4493