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Crushing and grinding are integral steps in the processing of solid minerals. There are several degrees of crushing from coarse crushing to ultra fine grinding. In crushing processes, crushers are used, in grinding processes, mills are used.
Despite the general purpose of crushers and mills, they are different in design and have their own characteristics of operating.
Crushers. More than 90% of crushers in the mining industry are jaw and cone crushers.
Mills. The most common type of mill in the mining industry is SAG and ball mills. Typical solutions for mills are the use of high pole induction and synchronous motors, both brush and brushless.
Vector control with proprietary algorithms with motor torque limitation and motor speed control in Triol VFDs provides reliable motor protection against overload and shaft breakage. If hard-to-crush material gets into the crusher, the motor develops a large torque. When the torque generated by the motor reaches the maximum allowable value, the inverter reduces the speed of the motor to ensure a safe torque value and therefore the motor current.
Torque Limitation Algorithm
The brake application was released at 200% torque limit setpoint without shaft block.
Accurate control of the motor torque and speed ensures that the motor rotation speed is reduced when the torque limiting algorithm is triggered, allowing the material to be crushed at a lower speed without stopping the crusher.
| Speed range |
1: 100 in open loop 1000 in closed loop |
| Speed accuracy (static) |
± 10% of rated motor slip in open loop ± 0.1% of rated motor speed in closed loop |
| Torque accuracy |
± 10% of rated motor torque in open loop ± 5% of rated motor torque in closed loop |
Our other solution is the Unblocking Mode which has a smooth change in the direction of rotation of the crusher in case of hitting hard-to-break rock. The mode allows you to crush the material without jamming the crusher by rotating back and forth and continue working non-stop.
Unblocking Mode
The algorithm of kinetic buffering ensures stable operation of Triol VFDs in case of deep and asymmetrical supply voltage dips, and even in case of its complete loss.
In the kinetic buffering mode, the maintenance of the VFDs operability is carried out due to the consumption of a part of the kinetic energy of the rotating mechanism with the subsequent instant restoration of the specified operating mode of the mechanism when the power supply is restored. The operating time of the inverter in this mode for crushers can be 5-10 periods of the mains voltage.
Oscillogram of Triol VFD operation in case of supply voltage failure
Vector control based on a mathematical model of the motor ensures smooth starting of mechanisms even at a full load with rated starting currents and without mechanical stress during starting. This allows the use of power cables for the motor and VFD with a smaller cross-section, reduces wear and extends the life of the crusher, and, accordingly, reduces the cost of implementation, maintenance and repair of the crusher.
Two-link energy conversion in Triol AT24 and AT27 VFDs allows the elimination of the negative effects of drawdowns, fluctuations and asymmetries of the mains voltage.
Medium-voltage VFDs Triol AT27 fully comply with the IEEE 519 standard without installing additional input filters and reactive power compensators. For low-voltage AT24 drives, it is possible to install passive input filters.
AT27 input current harmonic spectrum
The crusher speed optimization vector control algorithm reduces the consumed full motor power through high-precision control and optimization of the motor magnetic flux. This allows the reduction of energy consumption by up to 20%.
The picture presents the result of the measurement of the apparent power on different frequencies with the rated current.
Energy consumption decrease
Triol AT27 line MV with a degree of protection IP66 (NEMA4) and AT24 line UH with a degree of protection IP55 are solutions for use in places of processing rocks where there is a high content of dust and very often conductive. Both solutions have a dedicated cooling channel, which guarantees trouble-free and reliable operation of the inverter even in the most difficult conditions.
The “Master-follower” algorithm allows synchronous control of the operation of two VFDs and motors with an even distribution of the load between them. This eliminates unwanted dynamic effects and reduces maintenance costs.
Another solution from Triol is the use of low-voltage VFDs AT24 MP line. Independent control of each VFD with its own protection system provides flexible configuration of the complex for operation both in single-motor and multi-motor systems, and integration into a common main allows optimal distribution of power consumption between the mechanisms, depending on priorities.
Block diagram of the VFD AT24 MP line
Triol VFD AT27 line ED has the smallest dimensions in the world among variable frequency drives of its class at 6-11 kV!
The AT27 ED line variable frequency drives save not a few tens of centimeters but on average 25-30% of the area is occupied by the VFD.
The AT24VFDs of the SD line are a compact solution with all the necessary options installed inside the cabinet. The minimum cabinet width at high power density and the ability to install several VFDs close to each other allows the AT24 SD to be placed in almost any electric room.
The modular design of the AT24 inverter of the MP and SD lines and the AT27 VFD allows the cleaning and replacement of the air filters without stopping the VFD while ensuring the safety of personnel, and the time for repair is minimized due to modern design solutions and interchangeability of power cells.
The location of the cooling fans exclusively on the roof makes it easy to organize heat dissipation of the Triol VFD by connecting the air ducts directly to the drive roof around the fans. The heat released by the VFD during operation will not warm up the room but will be immediately removed from it, which will ensure a long and non-stop operation of the installation.
Starting with Anti Frozen charge detection that protects the mill lining and bearings from falling adhering material, which significantly increases the overhaul period. The starting algorithm is based on the starting torque of the motor. All changes in the motor torque are controlled by the control system of Triol VFDs and are quickly processed.
The motor vector control algorithm provides maximum torque even at zero speed, which ensures that the motor directly connected to the mill can be started without the use of a pneumatic clutch and does not require manual mill unloading. Triol VFDs significantly reduce mill downtime and minimize manual labor.
Low-frequency torque capability on the motor rated current
Vector control provides twice the motor torque at low frequencies compared to V / f control while maintaining the motor-rated current.
For synchronous motors in the AT27 drive, there is also a forcing excitation algorithm. It provides the rated field current of the synchronous motor before starting. In combination with motor vector control, motor torques up to 1.5 times the nominal are achieved. As a result, it allows the heaviest mills to be started even with frozen ore.
Starting with Anti Frozen charge detection that protects the mill lining and bearings from falling adhering material, which significantly increases the overhaul period. The starting algorithm is based on the starting torque of the motor. All changes in the motor torque are controlled by the control system of Triol VFDs and are quickly processed.
The motor vector control algorithm provides maximum torque even at zero speed, which ensures that the motor directly connected to the mill can be started without the use of a pneumatic clutch and does not require manual mill unloading. Triol VFDs significantly reduce mill downtime and minimize manual labor.
Low-frequency torque capability on the motor rated current
Vector control provides twice the motor torque at low frequencies compared to V / f control while maintaining the motor-rated current.
For synchronous motors in the AT27 drive, there is also a forcing excitation algorithm. It provides the rated field current of the synchronous motor before starting. In combination with motor vector control, motor torques up to 1.5 times the nominal are achieved. As a result, it allows the heaviest mills to be started even with frozen ore.
Kinetic buffering Algorithm ensures stable operation of Triol VFDs in case of deep and asymmetrical supply voltage dips, and even in case of its complete loss.
In the Kinetic buffering mode, the maintenance of the VFDs operability is carried out due to the consumption of a part of the kinetic energy of the rotating mechanism with the subsequent instant restoration of the specified operating mode of the mechanism when the power supply is restored. The operating time of the VFD in this mode for the mill can be from 5 to 100 periods of the mains voltage.
Oscillogram of Triol VFD operation in case of supply voltage failure
Vector control based on a mathematical model of the motor ensures smooth starting of mechanisms even at full load with rated starting currents and without mechanical stress during starting. This allows the use of power cables for the motor and frequency converter with a smaller cross-section, reduces wear and extends the service life of the crusher, and, accordingly, reduces the cost of implementation, maintenance and repair of the crusher.
Two-link energy conversion in Triol AT24 and AT27 VFDs allows eliminating the negative effects of drawdowns, fluctuations and asymmetries of the mains voltage.
Medium-voltage VFDs Triol AT27 fully comply with the IEEE 519 standard without installing additional input filters and reactive power compensators. For low-voltage AT24 VFDs, it is possible to install passive input filters.
AT27 input current harmonic spectrum
Inching mode involves rotating the mill very slowly (1 to 10% of rated speed) to visually inspect or grind the mill. This mode allows you to abandon the installation of an inching motor, as well as to simplify the gearbox of the mill. All movement of the mill is carried out only by the main motor.
The Inspection mode also eliminates the need for additional mill equipment. In this mode, the mill automatically moves to the specified number of the lining or the angular coordinate (determined by the operating personnel). The time for maintenance and replacement of the lining is significantly reduced.
The Controlled Stop function allows the mill to return to a standstill position at zero speed and torque. After receiving the stop command, the mill slows down and when zero speed is reached, the mill starts rotating at a low speed in the opposite direction. The process of gradually changing the direction of rotation of the mill allows it to stop smoothly without causing an emergency in the inverter. If stopped abruptly, the mechanical energy of the mill will be generated into the DC link capacitors of the VFD, which can lead to its failure.
In one enterprise, several mills are mainly installed. If the mill does not require speed control, then the AT27 VFD will make it possible to carry out a sequential soft start of each of the mills with the transfer of the motor power from the VFD to the main. This ensures a smooth start-up of the mills without stress for the mains, motors and the machine itself, and also reduces the investment in the project due to the use of a single VFD.
AT27 VFDs carry out high-quality control of various types of motors (up to 9 motors per 1VFD AT27) without additional costs:
- asynchronous squirrel-cage motors;
- induction motors with a phase rotor with short-circuited phase windings;
- synchronous brush and brushless motors.
The built-in algorithm for maintaining the cosine of synchronous motors allows both it to regulate the operation of the motor itself and to improve the cosine of the electricity consumed at the substation.
For dual pinion mills, the “Master-Follower” algorithm allows synchronous control of the operation of two VFDs and motors with an even distribution of the load between them. This eliminates unwanted dynamic effects and reduces maintenance costs.
Another solution from Triol is the use of low-voltage VFDs AT24 MP line. Independent control of each inverter with its own protection system provides flexible configuration of the complex for operation both in single-motor and multi-motor systems, and integration into a common main allows optimal distribution of power consumption between the mechanisms, depending on priorities.
Block diagram of the VFD AT24 MP line
A variety of lines of AT27 VFDs for outdoor performance allows you to choose the optimal solution for existing operating conditions in the open air, to save you from building buildings and also save you at least $ 40,000 in investment.
Triol VFDs: Profitable, Reliable, Convenient!
