The primary coil is connected to an ac voltage source. Delta and wye 3phase circuits this worksheet and all. Some quick points for solving problems on 3ph transformers with unbalanced loads aranya chakrabortty these types of problems will always consist of 3 elements. The transformer primary connected in either y or 2. It is connected to a 26kv, 800mva generator, which can be represented as a voltage source in series with a reactance of j 1. If the voltage and current to the motor are 400v and 8. For example, a farmer has a large, 480v, 3phase motor powering a well.
The transformer works on the principle of electromagnetic induction. To solve this problem, we will refer the circuit to the secondary lowvoltage side. The motor is in a building, and the farmer wants one 120v circuit. In which circuit y or delta are the phase and line currents equal. Umanand, principal research scientist, power electronics group, cedt, iisc bangalore for more detail. Two wattmeters connected to a 3phase motor indicate the total power input to be 12kw. Two wattmeters are connected to measure the input power to a balanced 3phase load by the twowattmeter method. A transformer has a primary coil and a secondary coil with the number of loops are 500 and 5000. Solution the equivalent circuit of this transformer is shown below. A three phase generator stepup transformer is rated 26kv. The purpose of a transformer is to change electrical voltage to a different value. A threephase transformer bank is to handle 500 kva and have a 34. The transformers for such circuits can be constructed either as a 3 phase bank of independent identical transformers can be replaced independently or as a single transformer wound on a single 3 legged core. Another calculation with a delta 3 phase source feeding a wye 3 phase resistive load.
A transformer is an electrical apparatus designed to convert. Solution of the next problem shows how equivalent circuit can be used to predict the performance. Calculate the iron losses of the transformer at normal voltage and frequency if its fullload efficiency be 95. Lecture series on basic electrical technology by prof. The secondary winding of a transformer has a terminal voltage of v t t s. If the instrument readings are 8kw and 4kw, determine a the total power input and b the load power factor.