approach unit
Synchronous motors show some interesting properties, which finds applications in power factor correction. The synchronous motor can be run at lagging, unity or leading power factor. The control is with the field excitation, as described below:When the field excitation voltage is decreased, the motor runs in lagging power factor. The power factor by which the motor lags varies directly with the drop in excitation voltage. This condition is called under-excitation.When the field excitation voltage is made equal to the rated voltage, the motor runs at unity power factor.When the field excitation voltage is increased above the rated voltage, the motor runs at leading power factor. And the power factor by which the motor leads varies directly with the increase in field excitation voltage. This condition is called over-excitation.The most basic property of sycho motor is that it can be use as a CAPACITOR OR INDUCTOR both. Hence in turn it improves the power factor of system.The leading power factor operation of synchronous motor finds application in power factor correction. Normally, all the loads connected to the power supply grid run in lagging power factor, which increases reactive power consumption in the grid, thus contributing to additional losses. In such cases, a synchronous motor with no load is connected to the grid and is run over-excited, so that the leading power factor created by synchronous motor compensates the existing lagging power factor in the grid and the overall power factor is brought close to 1 (unity power factor). If unity power factor is maintained in a grid, reactive power losses diminish to zero, increasing the efficiency of the grid. This operation of synchronous motor in over-excited mode to correct the power factor is sometimes called as Synchronous_condenser.
A synchronous motor becomes over-excited when the excitation level exceeds the synchronous reactance of the motor, resulting in a leading power factor. This condition typically occurs when the field current supplied to the rotor is increased beyond the rated value, causing the motor to generate excess reactive power. Over-excitation can lead to higher voltage levels and potential damage to the motor and connected equipment if not managed properly. It is important to monitor and control the excitation to maintain optimal performance and prevent overheating or other operational issues.
Power Factor measures the difference in phase between the current and voltage. When they are in phase the Power Factor is defined as 1. When out of phase the value is less than 1. If they are 180 degrees out of phase the Power Factor will be zero.
To improve the power factor
Synchronous impedance is not a constant because it varies with operating conditions such as load, frequency, and machine construction. It is defined as the ratio of the voltage to the current at synchronous speed, but this relationship changes depending on the reactance and resistance of the machine as well as the power factor of the load. Additionally, factors such as saturation of magnetic materials and temperature can also influence synchronous impedance, leading to variations in its value.
power factor normally goes to the lagging
A synchronous condenser (also known as a synchronous capacitor or synchronous compensator) is a DC-excited synchronous computer (large rotating generators) whose shaft is now not connected to any using equipment.
A synchronous motor is designed to convert electrical energy into mechanical energy to produce rotation, while a synchronous condenser is designed to only regulate voltage and improve power factor on the electrical grid without mechanical output. Both devices are synchronous machines that operate based on the principles of synchronous operation and require a magnetic field to be established.
Synchronous motors show some interesting properties, which finds applications in power factor correction. The synchronous motor can be run at lagging, unity or leading power factor. The control is with the field excitation, as described below:When the field excitation voltage is decreased, the motor runs in lagging power factor. The power factor by which the motor lags varies directly with the drop in excitation voltage. This condition is called under-excitation.When the field excitation voltage is made equal to the rated voltage, the motor runs at unity power factor.When the field excitation voltage is increased above the rated voltage, the motor runs at leading power factor. And the power factor by which the motor leads varies directly with the increase in field excitation voltage. This condition is called over-excitation.The most basic property of sycho motor is that it can be use as a CAPACITOR OR INDUCTOR both. Hence in turn it improves the power factor of system.The leading power factor operation of synchronous motor finds application in power factor correction. Normally, all the loads connected to the power supply grid run in lagging power factor, which increases reactive power consumption in the grid, thus contributing to additional losses. In such cases, a synchronous motor with no load is connected to the grid and is run over-excited, so that the leading power factor created by synchronous motor compensates the existing lagging power factor in the grid and the overall power factor is brought close to 1 (unity power factor). If unity power factor is maintained in a grid, reactive power losses diminish to zero, increasing the efficiency of the grid. This operation of synchronous motor in over-excited mode to correct the power factor is sometimes called as Synchronous_condenser.
A synchronous motor becomes over-excited when the excitation level exceeds the synchronous reactance of the motor, resulting in a leading power factor. This condition typically occurs when the field current supplied to the rotor is increased beyond the rated value, causing the motor to generate excess reactive power. Over-excitation can lead to higher voltage levels and potential damage to the motor and connected equipment if not managed properly. It is important to monitor and control the excitation to maintain optimal performance and prevent overheating or other operational issues.
Power Factor measures the difference in phase between the current and voltage. When they are in phase the Power Factor is defined as 1. When out of phase the value is less than 1. If they are 180 degrees out of phase the Power Factor will be zero.
To improve the power factor
A synchronous electric motor is an AC motor in which the rotation of the shaft is synchronized with the frequency of the ACsupply current; the rotation period is exactly equal to an integral number of AC cycles. Synchronous motors contain electromagnetson the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current. The rotor turns in step with this field, at the same rate.Another way of saying this is that the motor does not rely on "slip" under usual operating conditions, and as a result produces torque at synchronous speed. Synchronous motors can be contrasted with induction motors, which must slip in order to producetorque. The speed of the synchronous motor is determined by the number of magnetic poles and the line frequency.Synchronous motors are available in sub-fractional self-excited sizes to high-horsepower direct-current excited industrial sizes. In the fractional horsepower range, most synchronous motors are used where precise constant speed is required. In high-horsepower industrial sizes, the synchronous motor provides two important functions. First, it is a highly efficient means of converting AC energy to work. Second, it can operate at leading or unity power factor and thereby provide power-factor correction.
Synchronous impedance is not a constant because it varies with operating conditions such as load, frequency, and machine construction. It is defined as the ratio of the voltage to the current at synchronous speed, but this relationship changes depending on the reactance and resistance of the machine as well as the power factor of the load. Additionally, factors such as saturation of magnetic materials and temperature can also influence synchronous impedance, leading to variations in its value.
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The big difference is that the synchronous motor's rotor can have a variable current applied to it through its field slip rings. Both types of motors have their own advantages. With a synchronous motor in the system, the systems power factor can be regulated.
PHASE ADVANCER:phase advancers are used to improve the power factor of induction motors.The low power factor of an induction motor is due to the fact that its stator winding draws exciting current which lags behind the supply voltage by 90 degree.If the exciting ampere turns can be provided from some other A.C. source,then the stator winding will be relieved of exciting current and the power factor of the motor can be improved.This job is accomplished by the phase advancer which is simply an A.C exciter.The phase advancer is mounted on the shaft as the main motor and is connected in the rotor circuit of the motor. It provides exciting ampere turns to the rotor circuit at slip frequency.By providing more ampere turns than required,the induction motor can be made to operate on leading power factor like an over-excited synchronous motor.