Run Capacitors for motors
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Capacitors are electrical devices that can discharge and electrocute. Any electrical device should be powered down before removing and replacing parts.
Capacitors are electrical devices used in split phase electric motors to assist in starting and running.
The run capacitor is designed to be used continuously in the motor circuit.
They are similar to a rechargeable battery that can be discharged and charged very quickly. The video below demonstrates how the capacitor is similar to a battery.
The run capacitor is designed to be used continuously in the motor circuit.
They are similar to a rechargeable battery that can be discharged and charged very quickly. The video below demonstrates how the capacitor is similar to a battery.
So, how are capacitors made?
Without getting into specifics about how they work electronically, let's see what's inside.
Without getting into specifics about how they work electronically, let's see what's inside.
Run capacitors
The run cap is used to provide moderate starting torque for PSC fan motors.
They also increase efficiency of the motor when running. They are wired into the circuit permanently. For more on these types of motors, look here.
These capacitors are usually encased in metal. The reason for the metal case is to help transfer heat out of the capacitor.
Inside the case there is a type of oil that can easily transfer heat.
Up until the 1970s, the oil used was PCB oil. This oil was very stable. It would not break down or catch fire. The problem with this oil is its effect on the environment. It is considered as a hazardous waste and was removed from all capacitors.
The replacement oils are all flammable and so present a fire hazard, albeit a small one. The video below looks at 2 run capacitors and the oil inside. Both of the oils will burn. This video will not be available until 10-26-2014.
So, beside the oil, what's inside. Capacitors are very simple in construction.
You can make one by layering aluminum foil and cardboard and attaching every other foil to an electrode.
The video below disassembles a run capacitor. This video below will not be available until 10-28-2014
You can make one by layering aluminum foil and cardboard and attaching every other foil to an electrode.
The video below disassembles a run capacitor. This video below will not be available until 10-28-2014
So, if I am using 2 or more capacitors, what happens if I wire them in series or parallel?
Parallel wiring simply adds the strength of each capacitor to the other. The voltage capacity stays the same.
Series wiring is another matter.
When the capacitors are wired in series, there is a calculation to determine what the capacitance is. In any case, the capacitance of 2 or more capacitors in series will be less than either of the caps used. The video below includes this calculation. The voltage of the capacitors is added together when in series.
So, why would I use more than one capacitor? When I am confronted with a unit that needs a size of capacitor that I do not have with me.
Parallel wiring simply adds the strength of each capacitor to the other. The voltage capacity stays the same.
Series wiring is another matter.
When the capacitors are wired in series, there is a calculation to determine what the capacitance is. In any case, the capacitance of 2 or more capacitors in series will be less than either of the caps used. The video below includes this calculation. The voltage of the capacitors is added together when in series.
So, why would I use more than one capacitor? When I am confronted with a unit that needs a size of capacitor that I do not have with me.
For most HVAC applications, either the 370 volt or the 440 volt capacitor will be used. The choice of which capacitor is used depends on the manufacturers specs. When considering which voltage to be used, remember, a 440 volt cap may be used in an application where a 370 volt cap was specified. However, a 370 may not be used in a 440 volt application.
The run capacitor is part of the start system of the PSC motor. The video below is a demonstration of the capacitor start characteristics.
The run capacitor is matched to the individual motor it is used on. The video below shows what happens when the capacitor is too small.
More coming
