Purpose of Centrifugal Switch in Induction Motor

In the common Induction Motor which are used in drill presses, furnaces, table saws, pumps, grinders, washers and dryers, normally have a Centrifugal Switch. Centrifugal Switch is required together with an additional winding to start the motor. An induction motor has no copper windings in the turning rotor part; windings are only in the fixed … Read more

Why not Blocked Rotor Test by Keeping Induction Motor Rotor Winding Open?

As discussed in the previous post Blocked Rotor Test of Induction Motor, the rotor is prevented from rotating and then a small voltage is applied to the stator sufficient to pass the rated current through the stator winding and then leakage impedance of Induction Motor is calculated. The question may arise that why don’t we … Read more

Buchholz Relay – Construction and Working Principle

Buchholz relay is a gas actuated protection relay which is generally used in large oil immersed transformers of rating more than 500 kVA. It is used for the protection of a Transformer from the faults occurring inside the transformer. A typical Buchhloz Relay is shown below.   The gas actuated protective relay is designed to … Read more

Transformer Testing

For the purpose of quality assurance and ensuring that the finished transformer conforms to customer requirements and is ready for service a barrage of tests are performed on the transformer. These can be broadly classified into the following 3 types: Routine Test, Type Test and Special Test. 1) Routine Tests: These are standard tests performed … Read more

Difference between Brushed and Brushless Motor

Brushes are used in two main types of motors: DC motors and large synchronous motors, called wound-rotor synchronous motors. There is a third case in which brushes was used, the wound-rotor induction motor that has been obsolete for many years. In the DC motor case, the brushes transfer current into the rotor via the commutator. … Read more

Basics of Stepper Motor

A Stepper Motor is a special form of AC Motor. The input of this motor is in the form of electric pulse. For each input pulse,motor shaft turns through a specified degree, called Step. The Step size may vary from 0.72° to 90°. This means that motor shaft may turn from 0.72° to 90° for … Read more

BDV Test in Transformer

BDV test means Breakdown Voltage Test. It is done for checking the dielectric strength of the oil of the Transformer. Dielectric strength means the maximum capacity to withstand voltage of insulating oil. This test shows the dielectric strength of Transformer oil. In transformer oil has mainly two purposes, first for insulation, second as cooling of … Read more