Advantages of Variable Speed Drive over Soft Starter on Crusher
Variable speed drive (VSD) with vector control is able produce higher torque in motor shaft than star delta or soft starter while also drawing less current from the power supply network. If starting torque is not an issue in the crusher installation, the start delta or soft starter are both OK. (Provided that the electrical network is strong enough to manage the current rush) If you want to limit current rush in start or jam situation or you want to get higher starting torque then vector controlled variable speed drive is a good choice and even better if closed loop with speed feedback from motor to variable speed drive.
Variable speed drive solution will solve in most cases the torque problem when using standard asynchronic motor. Soft starter that reduce the toque might not deliver the required torque in effort to get to full speed. In case no need for speed regulation variable speed drive with synchronize bypass system can solve the problem This way you can have high torque during start, low current and after getting into full speed you bypass the variable speed drive and save all the energy loses and noises that variable speed drive can cause.
Energy saving with variable speed drive is achieved due to better control of magnetizing and rotor currents. It optimizes total current to motor thus reduces motor (and network) losses caused by excess current. If you use speed control, it is good to set a torque limit to control the maximum torque produced. If in torque control, then speed limit is needed.
The way we have solved an application while working for Gozuk was to use a variable speed drive in vector control mode for the start of the jaw crusher. Once the machine is started the variable speed drive was bypassed and the motor worked direct on line.
The main advantage of this solution is its robustness. Once the machine started and the variable speed drive bypassed the direct on line connected motor is not easily stopped by any rock jam. There is no torque limitation required by the variable speed drive. During the bypassing a current burst occurs but at this point the machine is unloaded and it is not a big problem. The variable speed drive can be used to jog the crusher in the event that it has been stopped with material inside.
Variable speed drive solution will solve in most cases the torque problem when using standard asynchronic motor. Soft starter that reduce the toque might not deliver the required torque in effort to get to full speed. In case no need for speed regulation variable speed drive with synchronize bypass system can solve the problem This way you can have high torque during start, low current and after getting into full speed you bypass the variable speed drive and save all the energy loses and noises that variable speed drive can cause.
Energy saving with variable speed drive is achieved due to better control of magnetizing and rotor currents. It optimizes total current to motor thus reduces motor (and network) losses caused by excess current. If you use speed control, it is good to set a torque limit to control the maximum torque produced. If in torque control, then speed limit is needed.
The way we have solved an application while working for Gozuk was to use a variable speed drive in vector control mode for the start of the jaw crusher. Once the machine is started the variable speed drive was bypassed and the motor worked direct on line.
The main advantage of this solution is its robustness. Once the machine started and the variable speed drive bypassed the direct on line connected motor is not easily stopped by any rock jam. There is no torque limitation required by the variable speed drive. During the bypassing a current burst occurs but at this point the machine is unloaded and it is not a big problem. The variable speed drive can be used to jog the crusher in the event that it has been stopped with material inside.