A capacitor is an electrical component of an HVAC (Heating, Ventilation, and air conditioning) systems. It is a medium through which energy is stored and either released suddenly or over a period of time. The most important role of a capacitor is to ensure that a motor starts spinning and keeps spinning in the proper direction.

The starting of a motor requires more energy than sustaining its momentum once it starts running. It is the duty of the capacitor to ensure that the unit receives the extra burst of electricity needed to get it going. A motor capacitor like a start capacitor or a 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.

J. Gardner Electric Motor Repairs prides itself in being the best selling and servicing electric motors since 13/3/1953. At Electric Motors Online, we are a one-stop destination when you are looking for the best motor capacitors. Our team is knowledgeable and well trained and here is everything you need to know about a start capacitor by our experts. It includes the following:

  • What Is the Capacitor Made Of?
  • Purpose of a Capacitor for Motors
  • Start Capacitor & Run Capacitor

What Is the Capacitor Made Of?

The capacitor as we know it today was originally referred to as a "condenser", is a passive electronic component. This component contains a minimum of two conductors or plates that are separated by an insulator (dielectric). These conductors can be thin films of various materials like metal, aluminium, foils or even disks while the insulator could be glass, ceramic, plastic film, air or paper. When the capacitor is connected to a voltage source, it stores an electrical charge in the form of an electrostatic field between its conductors. A battery is different from a capacitor. A battery uses chemicals to store an electrical charge and discharge it slowly through a circuit while a capacitor releases its energy much more rapidly.

Purpose of a Capacitor for Motors

The major purpose of the capacitor is to create a poly-phase power supply from a single-phase power supply. The motor along with a poly-phase supply is able to do the following:

  • Set the rotation direction
  • Provide start torque for the motor and increase the torque during operation.

Start Capacitor & Run Capacitor

As discussed, a capacitor is an energy storing device. The energy or the capacitance of an electric capacitor is measured in the form of micro-farads. There are two major types of capacitors - start capacitor and run capacitor

Start Capacitor

The start capacitor is found in the circuit of start windings when the motor is starting. This kind of capacitor contains a higher capacitance than a run capacitor. A start capacitor usually measures between 70 and 120 micro Farads. It provides an immediate electrical push to get the motor rotation started. If there is no start capacitor and the voltage is applied, then the motor would just hum. The start capacitor creates a voltage lag in the separate start windings of the motor. Due to this, the current builds up slowly, and the armature has an opportunity to begin rotating with the field of the current.

Run Capacitor

A run capacitor uses the charge in the dielectric to boost the current that provides power to the motor. A run capacitor is used to maintain a charge. In Ac units, there are dual run capacitors. One capacitor provides power to the fan motor while the other is responsible for sending power to the compressor. The run capacitors measure in at approximately 7-9 microFarads. It is also important to remember that the value or rating of the run capacitor must be accurate. If the value is too high, then the phase shift will be less than perfect which will make the winding current go too high. Similarly if the capacitor value or rating is too low, then the phase shift will be higher and the winding current will be too low. If the run capacitors are not ideal, then the motor could overheat and the true torque will not be enough to drive the current.

At Electric Motors Online we sell and service all electric motors. We specialise in rewinding AC and DC motors and service all kinds of makes and brands. We source and use only the best quality materials. In addition to this, we stock an extensive range of spare parts such as carbon brushes, fans, cowls, terminal blocks and boxes, capacitors and slip rings. We provide you with prompt and reliable customer service that ensures minimal disruption to your business when there is a sudden or unexpected breakdown. Additionally, we provide you with after-hours service and on-site attendance when you need them.

We provide you with an array of capacitors, compressor motors, general-purpose motors, metric motors, metric ODP motors and much more. We are 'Your Electric Motor Specialists'. We service all makes and brands including ABB, Baldor, CMG, Leroy-Somer, Teco, Toshiba, Sasco & WEG.

Our work speaks for itself, our range of motors includes 3 phase high-efficiency motors, 3 phase standard motors, Servo motors, Multi Speed motors, D.C motors, Hazardous location motors, Single phase motors, Compressor motors, Evaporative fan motors, Brake motors, Gearboxes, AC variable speed drives, Swimming pool pumps, Solar pumps and Submersible pumps. We are your electric motor specialists. Our qualified staff is always on toes to assist and provide you with professional advice when you have a dilemma whether to repair or replace a problem motor. For more information, connect with us today on (03) 9555 0331 or visit https://www.electricmotorsonline.com.au/capacitors/start.html