What happens to motors if you are using a higher rated capacitor?
Many times electrician or electrical engineers connect higher value of capacitor to singe phase motors, in our use fan motor,ac motors,water pump motors etc.
Non technical person or some technical person even does not know that higher value of capacitor how affect the performance and life of single phase motors.
Here we discuss some similar questions :
👉What happens to motors if you are using a higher rated capacitor?
👉My ceiling fan's capacitor is of 2.25 uF. What will happen if I connect a capacitor of 2.5 uF?
👉Can one replace a capacitor with a low value with one with a higher value but of the same voltage?
👉My A/C fan's capacitor is of 2.5 uF. What will happen if I connect a capacitor of 5 uF?
👉Single phase induction motor - What happens to motors if you are using a higher rated capacitor?
All motors including single phase motors like fan motors,ac motors,water pump motors etc.
are designed for optimum performance for their applications, supply conditions and variations.
Any change in rated values will cause it to degrade the performance, depending upon how much the deviation.
Here we discuss about What happens to motors if you are using a higher rated capacitor?
As you know
C = Q/V
THAT MEANS PER VOLT CHARGE GIVING CAPACITY OF CAPACITOR .
C = 1/V
Thus Capacitance (C) is inversely proportional to Voltage drop (V). If we increase the capacitance, Voltage drop across Capacitor decreases.
As capacitor is directly connected to induction motor, motor will receive higher voltage. Higher the voltage to motor higher the current(with same resistance), V = IR .
So with higher current more the emf induced , higher the magnetic flux generated and the RPM of fan increases.
But the disadvantage is I^2R losses increases as current increases, thus fan will take higher input wattage and thus more units of electricity. Due to this higher power access heat is generated.
this access heat insulation of windings should damage.
Using higher value of capacitance also reduces the life of motor windings.
2.25 mfd capacitor , taken with tolerance limits of 5%, comes closer to 2.5 mfd lower limits, but if 2.5 mfd tolerance is on higher side of tolerance, it will cause a deterioration in performance. Of course, 2.5 mfd capacitor gives a little higher fan speed, at least at the time it is connected.
Most capacitors in fans today use Metallized capacitors, which have a tendency to reduce in value over time - though it takes a few years for a good product.When this happens, fan speed goes down
Electricians, sometimes even engineers, have developed a habit of using 2.5 mfd to replace 2.25 mfd, the logic being its value will come within limits of 2.25 mfd after reducing, and will last longer.
All electrical components (Resistors, Capacitors, Inductance) have +/- 5% to +/- 20% acceptable variations called as tolerance.
The actual capacitance 2.25 mfd capacitor varies between:
2.02 mfd to 2.47 mfd for 10% tolerance
2.13 mfd to 2.36 mfd for 5% tolerance.
Conclusion :
If you connect 2.5 uf capacitor instead of 2.25 uf capacitor,the capacitive reactance become low so voltage drop across the capacitor become low so voltage across the winding of the motor is increases.we know that resistance of the winding is fix so current through the winding is increases and Motor winding get heated due to I^2R losses and after some time insulation of wingding get damage due to this access heat , some time starting winding may burn.
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