Capacitor Start Capacitor Run Motor Pdf Free !NEW!
A motor capacitor, such as a start capacitor or run capacitor (including a dual run capacitor) is an electrical capacitor that alters the current to one or more windings of a single-phase alternating-current induction motor to create a rotating magnetic field.
Capacitor Start Capacitor Run Motor Pdf Free
Start capacitors briefly increase motor starting torque and allow a motor to be cycled on and off rapidly. A start capacitor stays in the circuit long enough to rapidly bring the motor up to a predetermined speed, which is usually about 75% of the full speed, and is then taken out of the circuit, often by a centrifugal switch that releases at that speed. Afterward the motor works more efficiently with a run capacitor.
The motor will not work properly if the centrifugal switch is broken. If the switch is always open, the start capacitor is not part of the circuit, so the motor does not start. If the switch is always closed, the start capacitor is always in the circuit, so the motor windings will likely burn out. If a motor does not start, the capacitor is far more likely the problem than the switch.
Run capacitors are designed for continuous duty while the motor is powered, which is why electrolytic capacitors are avoided, and low-loss polymer capacitors are used. Run capacitors are mostly polypropylene film capacitors (historically: metallised paper capacitors) and are energized the entire time the motor is running. Run capacitors are rated in a range of 1.5 to 100 µF, with volt classifications of 250, 370 and 440 V.
A dual run capacitor supports two electric motors, with both a fan motor and a compressor motor. It saves space by combining two physical capacitors into one case. The dual capacitor has three terminals, labeled C for common, FAN, and HERM for hermetically-sealed compressor.
Dual capacitors come in a variety of sizes, depending on the capacitance (measured in microfarads, µF), such as 40 plus 5 µF, and also on the voltage. A 440-volt capacitor can be used in place of a 370-volt, but not a 370-volt in place of a 440-volt. The capacitance must remain within 5% of its original value. Round cylinder-shaped dual run capacitors are commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor. An oval dual run capacitor could be used instead of a round capacitor; in either case the mounting strap needs to fit the shape used.
The units of capacitance are labeled in microfarads (µF). Older capacitors may be labeled with the obsolete terms "mfd" or "MFD" which can be ambiguous but are, especially in this context, used for microfarad as well (a millifarad is 1000 microfarad and not usually seen on motors).
A faulty run capacitor often becomes swollen, with the sides or ends bowed or bulged out further than usual; it can then be clear to see that the capacitor has failed, because it is swollen or even blown apart causing the capacitor's electrolyte to leak out. Some capacitors have a "pressure sensitive interrupter" design that causes them to fail before internal pressures can cause serious injury. One such design causes the top of the capacitor to expand and break internal wiring.
The motor capacitor, which is a component of a hot tub circulating pump, can overheat if defective. This poses a fire hazard, and the U.S. Consumer Product Safety Commission (CPSC) has received more than 100 reports of incidents of overheating of the motor capacitor, with some fires started.
Motor capacitors manufactured before 1978 likely contain polychlorinated biphenyls (PCBs). These are extremely toxic and persistent chemicals with many long-lasting negative human and wildlife health effects. Capacitors were required to be labeled in the U.S. with "No PCBs" or similar language. Capacitors without these labels are suspect.
PCB containing capacitors must be replaced, and disposed by consulting local environmental authorities. If these capacitors leak or fail pcbs can be released into the environment and will very likely result in extremely expensive environmental cleanups, and potentially, lawsuits. There are extensive toxicological reports on PCBs in the research community. U.S. EPA has much information on the correct way to test and manage these toxic chemicals in older capacitors".
The capacitor-start capacitor-run motor is a type of single-phase induction motor. The capacitor-start capacitor-run induction motor is also known as two value capacitor motor. The schematic diagram of a capacitor-start capacitorrun induction motor is shown below.
The capacitor-start capacitor-run induction motor consists of a squirrel cage rotor and its stator has two windings, viz. the starting or auxiliary winding and the main or running winding. The two windings are displaced by an angle of 90 in the space.
During the normal operation of the motor, the rated line current should be smaller than the starting current. Therefore, the capacitive reactance of the running capacitor should be high and is given by,
As the motor attains the normal speed, the starting capacitor (CS) is disconnected from the motor circuit by a centrifugal switch (S) and the running capacitor (CR) remains permanently connected in the circuit. Since one capacitor (CS) is used only at starting and the other capacitor (CR) for continuous running, the motor is known as capacitor-start capacitor-run motor.
The phasor diagram of the capacitor-start capacitor-run motor is shown below. At starting both the capacitors are in the circuit, therefore, the phase angle φ is greater than 90. When the starting capacitor (CS) is disconnected from the circuit, then the phase angle becomes 90 electrical.
This motor has a cage rotor, and its stator has two windings namely the main winding and the auxiliary winding. The two windings are displaced 90 in space. The motor uses two capacitors CS and CR. In the initial stage, the two capacitors are connected in parallel.
1. Two-value capacitor motors are used for loads of higher inertia that require frequent start.2. These are used in pumping equipment.3.These are used in refrigeration, air compressors, etc.
This article gives electric motor start-run capacitor installation & wiring instructions for electric motor capacitors designed to start & run an electric motor such as an AC compressor, heat pump compressor or a fan motor, and how to wire up a hard-starting air conditioner compressor motor, fan motor, to get an air conditioner, heat pump, refrigerator, or freezer compressor or other electric motor (such as a well pump) going.
This electric motor capacitor article series explains the selection, installation, testing, & use of electric motor starter start and run capacitors used on various electric motors found in or at buildings such as air conditioner compressors, fan motors, some well pumps and some heating equipment.
Whether you are simply installing a replacement start or run capacitor, or you are installing a "hard-start" capacitor to try to keep a troublesome electric motor going, the procedures for choosing and installing the capacitor are the same.
When an electric motor, such as an A/C motor, is having trouble starting, it's common for the service technician to simply try swapping-in a new starting capacitor. That's because that step is quick, easy, and inexpensive.
But keep in mind that the underlying problem might be a more serious failure inside the motor itself, such as a broken start or run motor winding or a failed motor bearing. In a single phase (common residential A/C) compressor you can verify with an ohmmeter whether or not the A/C compressor is bad. We describe that procedure separately
In our capacitor testing and wiring sketch above and in our explanatory table below, you note we use the letters S, C, and R to identify the usual terminals to which a start/run capacitor is wired. On many systems these terminals may already be labeled so that the three leads on a start/run capacitor can be wired correctly:
Watch out: Turn off electric power before checking or touching electric motor terminals or performing tests. You may also need to discharge any capacitor terminals to ground to avoid getting a shock.
Watch out: live high voltage may also be present at a capacitor, capable of giving a tremendous electrical shock even after electrical power has been disconnected at the equipment. Never work on live electrical equipment.
Relay and hard start capacitors such as the Starter Pow-R-Pak sold by Sealed Unit Parts Co., can be installed with no wiring changes to the original system whatsoever. Quoting from Part No. SPP-5, a relay and hard start capacitor sold by that company:
Here are some sample capacitor installation instructions for adding a motor starter capacitor to an air conditioning compressor motor - taken from the product package for a relay and start capacitor intended for use on a refrigerator or freezer. Similar starter capacitors are available for air conditioning compressors.
Start/run electric motor capacitors can be mounted in any direction or position. However there are some other capacitor mounting considerations that can affect capacitor life: basically you want to minimize the capacitor's exposure to vibration and heat.
It is advisable to make an experimental measurement of the temperature reached by the capacitor under the working conditions in the final application and after the thermal equilibrium has been achieved." - Supco