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Why does a synchronous generator typically run at lagging power factor?
Wiki User
∙ 16y ago
When a synchronous generator is running at lagging power factor the current it supplies lags its terminal voltage. Thus it acts as a source of reactive power, or magnetizing vars.
Reactive power is needed to create the magnetic fields in devices such as Transformers and induction motors.
The Power factor of a utility depends on the type of load it supplies. Usually the Loads on utility are inductive loads (where the current lags behind the Voltage) and hence the power factor at which the utility operates is lagging. Most loads connected to utility are inductive loads like motors, fans, rolling mills which cause the power factor of the utility to be of lagging in nature.
Wiki User
∙ 16y ago
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When synchronus generator is supplying active and reactive power it is operating at leading or lagging power factor?
A synchronous generator is operating at lagging power factor (positive P & Q) when it is supplying P & Q to the system. P & Q are positive which means that they are flowing away from the bus where the generator is connected (overexcited case). On the other hand, it is operating at leading power factor when it is supplying P and absorbing Q. The sign of Q is negative which means that it is flowing towards the generator bus (underexcited case).
When a load on a normally excited synchronous motor is increased its power factor tends to?
power factor normally goes to the lagging
What is the full load current of 200kW 380V 3-phase generator with 0.8 lagging power factor?
304 Amperes
When you should use synchronous motor instead of capacitor for power factor correction?
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.
Can we improve generator power factor for increasing active power?
The 0.8 Power Factor provided by generator manufacturers is not the load power factor, but it is the nominal power factor used to calculate the kW output of an engine to supply the power for a particular alternator kVA output. Alternators are therefore designed to supply their rated kVA at 0.8 lagging power factor.
How you improve power factor in synchronous motor?
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.
What is compounding curve in synchronous motor?
The operation of a synchronous generator delivering power to a constant power-factor load is demonstrated by means of compounding curves. A compounding curve shows the field excitation needed to maintain rated terminal voltage as the load is varied.
Leading and lagging power factor?
The terms, 'leading' and 'lagging' refer to what the load current is doing, relative to the supply voltage (Phase difference) -never the other way around. If the current is leading the voltage, then the power factor is 'leading'; if the current is lagging the voltage, then the power factor is 'lagging'.
Power factor lead or lag?
By definition, the terms 'leading' and 'lagging' refer to what the load current is doing with respect to the supply voltage. So, for a 'lagging power factor', it is the current that is lagging.
Why generators are rated at 0.8 lagging power factor?
Rated power factor
What reasons are there to want to correct a lagging power factor?
When you have a lagging power factor, measuring instruments (i.e. AC energy meters etc..) will read high. For example, if you've actually used 12W, when a lagging power factor is present, the meter might read 13~14W.
What the negative and positive sign shows for power factor?
Applying a negative or positive sign to power factor is an obsolete method of describing whether it is 'leading' or 'lagging'. We no longer do this. These days, a 'leading power factor' indicates that the load is capacitive and the load current is leading the supply voltage, and a 'lagging power factor' indicates that the load is inductive, and the load current is lagging the supply voltage. Having said that, a 'negative' power factor is also the mathematical consequence of 'negative power' -i.e. the direction of power when it is fed from the load back to the supply (e.g. when the grid feeds energy into a generator, causing it to 'motor'). In this case, the power factor isn't really negative, but simply appears to be so.
