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Feb 23, 2018· High no-load current: Motor not rewound. One situation in which higher-than-expected no-load current can occur is with reconditioned motors. Although some motors with no-load currents above or below the guidelines shown in Table 1 may still be satisfactory, motors with no-load current outside of these ranges warrant further analysis.
sense to consider using VSDs with standard Squirrel cage motors on mill applications. When using a VSD to run an ac induction motor there are a number of benefits for the user. Slipring motor and LRS - compared to squirrel cage and VSD Starting current and torque Ac Squirrel cage motors draw around 500% to 900% of Full Load
motor inrush current. • The type of motor selected affects the inrush current in the motor circuit. Induction and synchronous motors have different reactances and inrush currents depending on the number of poles/speed of the motor. Another factor in the selection of the starting method is the voltage drop permissible at a given location.
causes of high current on sag mill motors 4.9 - 6761 Ratings ] The Gulin product line, consisting of more than 30 machines, sets the standard for our industry.
Q: For now I am working on a mining project which involves starting two SAG mills, the method of starting these mills is by rotor resistance and likewise we are using an energy recovery system (SER), could someone tell me how this system works SER? Each mills have two motors of 8000 kW at 13.8 kV.
Whether or not a voltage sag causes a problem will depend on the magnitude and duration of the sag and on the sensi-tivity of your equipment. Many types of electronic equipment are sensitive to voltage sags, including variable speed drive controls, motor starter contactors, robotics, pro-grammable logic controllers, controller power supplies, and
In my opinion, current imbalance on motors of a twin Pinion Mill Drive train is caused by inaccurate load sharing. Power supply to the motor has no effect as it is passive and power is drawn as needed. Since this is a WRIM and LRS set up (no VSD with active load sharing or Quadramatic) the motors rely on natural load sharing.
Magnetic motor starters include ? that detect excessive current passing through a motor and are used to switch all types and sizes of motors. overload relays Although more expensive, open-circuit transition is preferable to closed-circuit transition because closed-circuit transition does not cause a high-current .
The fact is, numerous reasons can exist which causes a motor to trip that will not be seen by a Megger, such as a turn-to-turn short. Breakdown in the insulation between individual turns of a winding can occur inside a stator slot or at the end turn and be completely isolated from ground. ... These high zero sequence currents return to the ...
Cause: The common cause of this disturbance is switching on of the heavy appliances like motor or refrigerator or Air conditioner which require large start up power.Other reasons can be failure on the power lines and transformers. Prevention: Like surges, sag can be prevented by using voltage regulators and power conditioners.. BROWNOUTS. A brownout occurs when there is a steady decrease in ...
What are the most common causes of electric motors failure? ... greatly impact the motor. To avoid an over-current, there are some devices that need to be installed that can prevent it from ...
THE LOW SPEED MOTOR SOLUTION Due to the high torque required by the mill, low speed motors are generally synchronous machines. The mill is a low dynamic system therefore a brushless synchronous machine is best suited for this application. Brushless synchronous motors have no wearing parts, and the AC/ AC excitation power is kept small.
Impulsive transients are sudden high peak events that raise the voltage and/or current levels in either a positive or a negative direction. These types of events can be categorized further by the speed at which they occur (fast, medium, and slow). Impulsive transients can be very
Ball Mill SAG Mill Figure 2 Core pressing system with spring plate/washer and re-tightening statistics in a typical installation Access to the inside of the motor and the cooling system The easier the access to the inside of the motor is, the more convenient and efficient is the work on the motor.
Voltage sags – or dips which are the same thing – are brief reductions in voltage, typically lasting from a cycle to a second or so, or tens of milliseconds to hundreds of milliseconds. Voltage swells are brief increases in voltage over the same time range. Longer periods of low or high .
Feb 26, 2014· 1/Untrue, If so how would you control the rpm of a DC motor? Excess torque (load current) causes overheat. Low back EMF is accompanied with low applied voltage so the net effect is the same. 2/ If full voltage is applied on a stationary motor the current is initially limited only by the very low resistance of the armature.
There are several factors which cause a voltage sag to happen: Since electric motors draw more current when they are starting than when they are running at their rated speed, starting an electric motor can be a reason of a voltage sag. When a line-to-ground fault occurs, there will be a voltage sag until the protective switch gear operates.
Jun 22, 2009· The failure of the SAG mill motor follows a failure in March of one of two identical ball mill motors. The spare motor carried in the Operation's store was used on that occasion to minimise downtime. The motor damaged in March is expected to be repaired and returned to site in early July.
However, this motor initial current surge is "long", so in most cases a unrealistically large capacitor would be needed to make a significant difference. A small capacitor across a motor can help to reduce emissions. The capacitor keeps the voltage more steady, and keeps the high frequency noise current circulating close to the motor.
use of big mill grinding circuits, where large power gearless motor drives with cycloconverters in the range around 20 MW are being applied for semiautogenous (SAG) mills and re-cently, ball mills are also being considered. This work addresses some current issues involving design and application of high-power drives employed in SAG grind-
Apr 01, 2003· Overheating Electric Motors: A Major Cause of Failure. EP Editorial Staff | April 1, 2003 ... Even though the motor current may vary when applying overvoltages, the excessive damaging heat in the motor will not improve. ... Chemical abrasive substances in the air, wet operation, and high altitude operation are a few common environmental ...
These non-sinusoidal quantities (voltages and currents) can be divided into sinusoidal components, the fundamental frequency (i.e. 50 or 60 Hz) component and the harmonic components. Figure 3.3 shows the harmonic spectrum up to the 50th order of the "Trapezoid" shape AC current of Figure 3.2(a) as a percentage of fundamental current.
As a result while both phenomena can be disruptive in a system and cause considerable damage, generally speaking voltage surges are considered more damaging. This is due to the longer period of time in which the electric circuit must deal with the excessive power. What Causes Voltage Surges . Engineers generally recognize two causes of voltage ...
ABB's GMD is the most powerful mill drive system in the market to power semiautogenous (SAG), ball and autogenous (AG) mills, This 'workhorse' for grinding operations combines a robust, service-friendly and fit for purpose design to provide highest throughput, reliability .
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