Rating factor current transformer
transformer mentioned above having a rating of 480:120 volts will have a ratio of 4:1 and the current transformer having a rating of 400:5 amperes will have a ratio of 80:1. Answer: The TRF (Thermal Rating Factor) of a current transformer is the indication of the transformer’s overload capability. The number indicates the amount the primary load current may be increased over its rating without exceeding the allowable temperature rise. The standard rating basis of all current transformers is that the current transformer must be capable of carrying 100-percent rated current without exceeding 55 °C average The rating factor of the transformer indicates the maximum continuous current that can flow through a current transformer without exceeding the thermal capability of windings. Generally, the rating factor or RF range from 1 to 4. In the previous example, Rating Factor defined at room temperature at 30 degrees Celsius. The question, what is the rating factor (RF) value of a current transformer if the room temperature is change from 30 degree Celsius to 50 degrees Celsius.
Table 1: Minimum Current Transformer Window Diameter. Wire Continuous Thermal Current Rating Factor, frequently abbreviated to Rating Factor or. RF.
Unlike a voltage transformer, the primary current of a current transformer is not dependent of the secondary load current but instead is controlled by an external load. The secondary current is usually rated at a standard 1 Ampere or 5 Amperes for larger primary current ratings. The rating of transformer is given in terms of its kVA, HV/LV voltage and phase rotation (for three phase transformer). To calculate the rating of the transformer for both single phase and three phase, the load required to be fed and voltage at which load is to be fed must be known or should be calculated. Figure 1 – Current transformer nameplate. Go back to Content Table ↑ 1.4 Rated thermal short-time withstand current: I th (kA). This is the highest level of rms primary fault current which the CT can endure, both thermally and dynamically, for 1 second without damage.When used in a medium voltage enclosure, the I th rating should match the short-time withstand rating of the entire switchgear. But here in case of the transformer, the load is completely unpredictable, and the designer designed the transformer by considering the unity power factor. Thereby, the rating of the transformer is in KVA and not in KW. The rating of the transformer also expressed in VA, KVA and MVA depending on the size of transformer. In the previous example, Rating Factor defined at room temperature at 30 degrees Celsius. The question, what is the rating factor (RF) value of a current transformer if the room temperature is change from 30 degree Celsius to 50 degrees Celsius.
Unlike a voltage transformer, the primary current of a current transformer is not dependent of the secondary load current but instead is controlled by an external load. The secondary current is usually rated at a standard 1 Ampere or 5 Amperes for larger primary current ratings.
The rating of transformer is given in terms of its kVA, HV/LV voltage and phase rotation (for three phase transformer). To calculate the rating of the transformer for both single phase and three phase, the load required to be fed and voltage at which load is to be fed must be known or should be calculated. Figure 1 – Current transformer nameplate. Go back to Content Table ↑ 1.4 Rated thermal short-time withstand current: I th (kA). This is the highest level of rms primary fault current which the CT can endure, both thermally and dynamically, for 1 second without damage.When used in a medium voltage enclosure, the I th rating should match the short-time withstand rating of the entire switchgear. But here in case of the transformer, the load is completely unpredictable, and the designer designed the transformer by considering the unity power factor. Thereby, the rating of the transformer is in KVA and not in KW. The rating of the transformer also expressed in VA, KVA and MVA depending on the size of transformer. In the previous example, Rating Factor defined at room temperature at 30 degrees Celsius. The question, what is the rating factor (RF) value of a current transformer if the room temperature is change from 30 degree Celsius to 50 degrees Celsius.
Unlike a voltage transformer, the primary current of a current transformer is not dependent of the secondary load current but instead is controlled by an external load. The secondary current is usually rated at a standard 1 Ampere or 5 Amperes for larger primary current ratings.
Nov 7, 2011 Recently we had a question on CT (current transformer) sizing (often Kssc - rated symmetrical short-circuit current factor; K'ssc - effective Knee Point, Saturation Voltage, or C Rating, depending on the user's decision. = User' s Safety Margin Factor. The equation must be evaluated for all likely CT transformer mentioned above having a rating of 480:120 volts will have a ratio of 4:1 and the current transformer having a rating of 400:5 amperes will have a ratio of 80:1. Answer: The TRF (Thermal Rating Factor) of a current transformer is the indication of the transformer’s overload capability. The number indicates the amount the primary load current may be increased over its rating without exceeding the allowable temperature rise. The standard rating basis of all current transformers is that the current transformer must be capable of carrying 100-percent rated current without exceeding 55 °C average The rating factor of the transformer indicates the maximum continuous current that can flow through a current transformer without exceeding the thermal capability of windings. Generally, the rating factor or RF range from 1 to 4. In the previous example, Rating Factor defined at room temperature at 30 degrees Celsius. The question, what is the rating factor (RF) value of a current transformer if the room temperature is change from 30 degree Celsius to 50 degrees Celsius.
Transformer rating = 100 kV Primary voltage or H.V.= 11 kV Primary current= 5.25 A Secondary voltage or L.V.= 415 volts Secondary current= 139 A
Model# CTM-0C Bar Type Metering Current Transformer designed for indoor use . Suitable for operating meters, instruments and control devices.
Electrical Tutorial about Current Transformer Basics and Current Transformer and uses for current transformers such as with Wattmeter's, power factor meters, Most current transformers have a the standard secondary rating of 5 amps with Polycast testing capabilities include polarity, ratio and phase angle, saturation, temperature rise, open cir- cuit, induced, power factor, hipot, impulse, partial. A current transformer (CT) with higher accuracy will typically generate more revenue for This CT is only accurate at 0.3% from 600 amperes to the rating factor. The IEEE C57.13 standard addresses the “de-rating” of a current transformer's rating factor in Section 4.5 (see image to the left). A standard CT has To properly determine the Rating Factor, the maximum current rating of the bushing should be stated. To assure the. DBCT is properly sized for short circuit 600V Current Transformers Non-ANSI Rated Window Type. Page 1 of 2 CONTINUOUS THERMAL CURRENT RATING FACTOR: 200A at 30°c amb., 120A at