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A typical motor start capacitor. A motor capacitor [1] [2] 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. [citation needed] There are two common types of motor capacitors, start capacitor and run capacitor (including a dual run ...
This fast change in current consumption can pull the voltage of the rail down, or cause it to spike, creating a voltage ripple. This change in current happens much faster than the VRM can react. The switching current must therefore be handled by decoupling capacitors.
Power factor correcting capacitors can be added externally to neutralize a constant amount of the variable reactive excitation current. After starting, an induction generator can use a capacitor bank to produce reactive excitation current, but the isolated power system's voltage and frequency are not self-regulating and destabilize readily.
Squeezing the dielectric can change a capacitor at a few tens of bar pressure sufficiently that it can be used as a pressure sensor. [83] A selected, but otherwise standard, polymer dielectric capacitor, when immersed in a compatible gas or liquid, can work usefully as a very low cost pressure sensor up to many hundreds of bar.
A capacitor can store electric energy when it is connected to its charging circuit and when it is disconnected from its charging circuit, it can dissipate that stored energy, so it can be used as a temporary battery. Capacitors are commonly used in electronic devices to maintain power supply while batteries are being changed.
Parallel resonance or near-to-resonance circuits can be used to prevent the waste of electrical energy, which would otherwise occur while the inductor built its field or the capacitor charged and discharged. As an example, asynchronous motors waste inductive current while synchronous ones waste capacitive current.
It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage.
A sudden fail-open fault can cause multiple secondary failures if it is fast and the circuit contains an inductance; this causes large voltage spikes, which may exceed 500 volts. A broken metallisation on a chip may thus cause secondary overvoltage damage. [1] Thermal runaway can cause sudden failures including melting, fire or explosions.