It is the power of the ultrasonic instrument.
VA is the unit of apparent power of electrical appliances, because V is the unit of voltage, A is the unit of current, according to P = UI, so VA is the unit of power . The reason why it is not written as W (watt, also a unit of power, and is the international unit of power), because the use of W indicates the actual (or rated) power of the appliance.
W is VA multiplied by the output power factor. If the power factor is 0.6 or 0.7, then the corresponding W is 780, which means that the transformer can drive 780W of computer equipment.
Apparent power, used in the AC line, also known as capacity, is the product of voltage and current rms, the unit is volt-ampere (VA). Mostly used in designing lines and equipment. As a simple example, the unit of regulated power supply and UPS is VA, not watt. In the selection will not only consider the load power, but also consider the reactive component.
The significance of apparent power
Since the apparent power is equal to the product of the rms value of the current and voltage at the knob at the end of the network, and the rms value objectively reflects the magnitude of the sinusoidal quantity and his ability to do work, the product of these two quantities reflects the amount of energy that needs to be transferred from the external circuits to the network to ensure that the network can work properly or the capacity of the network.
Because there are both resistors in the network, such as energy-consuming components, but also the existence of inductors, capacitors, such as energy storage components, so the external circuit must provide its normal operation of the power required, that is, the average power or active power, at the same time, there should be a portion of the energy is stored in inductors, capacitors and other components. This is the reason why the apparent power is greater than the average power. Only then can the network or equipment work properly. If the average power to provide power to the network is not guaranteed to work properly.
So, in practice, the rated voltage and rated current are usually used to design and use the electrical equipment, and the apparent power is used to indicate its capacity.
Additionally, since the energy stored in inductors, capacitors and other components between one period of time will be released in other periods of time respectively