What Is Va Rating Of Current Transformer

Sometimes the transformer can be rated by kVA kilo Volt-Amps or MVA Mega Volt-Amp.

What is va rating of current transformer. Implies how much load can be connected to the secondary of the current transformer. The VA rating refers to the power distribution rating relative to how much power the transformer can deliver to the load. VA ratings are also often used for transformers. The knee-point voltage is less applicable for metering current transformers as their accuracy is generally much higher but constrained within a very small range of the current transformer rating typically 12 to 15 times rated current.

For a typical 24 volt secondary this is simply using watts law to calculate amperage. Transformers with the same sized core usually have the same VA rating. Transformer rating 100 kV Primary voltage or HV 11 kV Primary current 525 A Secondary voltage or LV 415 volts Secondary current 139 A. The kVA unit represents kilovolt-amperes or 1000 volt-amperes.

Go back to Content Table Sources. In a DC circuit 1 VA is the equivalent of one watt 1 W. Each of these current sensors is affected by a VA rating. Hence the transformer is rated by the VA only.

Maximum output current is then VA rating divided by nominal output voltage. The rated VA indicates the load the transformer can take. Simply put the VA rating is the math formula used in determining the amperage at a given voltage. Volt-ampere VA is a measurement of power in a direct current DC electrical circuit.

Common current outputs include 5A 1A 01A or a low mA output. This is a metering class rated current transformer. The total deliverable apparent power is the rating of the transformer. Calculating the burden of a Current Transformer.

To calculate VA you need to know the supply voltage and the current delivered to the load. The rating is the load carrying capability of the machine. The fuse must be smaller than the VA rating of the transformer. A 40 VA transformer is rated for 40 VA or Volt-Amps on the secondary.

A transformer with a 100 VA rating for instance can handle 100 volts at one ampere amp of current. The convention of using the volt-ampere to distinguish apparent power from real power is allowed by the SI standard. The VA specification is also used in alternating current AC circuits but it is less precise in this application because it represents apparent power which often differs from true power. A nameplate of three phase transformer has the following parameters.

This is a protection class rated current transformer. 40 24 1666666 round up to 167 already So you cannot place more than 167 amps of constant load on the transformer without overloading it. VA stands for volt-amperes. Note that CTs with a voltage output regardless whether AC or DC are burdened with a resistor inside of the CT and do not have VA ratings.

But the alternator and the transformer are the only machines which are rated in volt-amp VA. The machines are always rated in watts. For example if your measuring CT is rated for 15VA burden you can connect 3 measuring instruments. The unit of apparent power is VA Volt-Amp.

The burden is specified as VA or resistance or impedance. The VA rating is used to select the properly sized fuse for that circuit. Or P V x I Secondary voltages x Secondary Current P 415V x 1391A 57726 VA 5772kVA Once again we noticed that the rating of Transformer on Nameplate is 100kVA but according to calculationit comes about 57kVA The difference comes due to ignorance of that we used single phase formula instead of three phase formula. The current transformer is connected to a measuring instrument or a protective relay by means of wires.

This example indicates a current transformer with an accuracy of 12 and a maximum allowable secondary burden of 02 O or 5 VA on a 5 A secondary CT. Medium Voltage Application Guide by Aucom. This will then determine the maximum load that can be connected to the transformer. You get the supply voltage from the voltage specifications associated with the primary and secondary windings.

Many of our customers regularly request quotes for standard and custom 5A ratio type current transformers but only ask for the window size and the input current with no knowledge of the burden. The burden of a current transformer is indicated in its nameplate. A transformer with a 10 kVA rating is the same as a transformer with a 1000 VA rating and can handle 100 volts at 10 amps of current. The burden is rated in VA.

Why do you care about burden when ordering current transformers.