Synchronous motors are not self-starting. The DC source is applied to the rotor of the synchronous Motor.
The factor by which, the induced E.M.F gets reduced due to short pitching is called pitch factor or coil span factor denoted by Kc. It is given as
Kc = cosα/2
α = 60°
Kc = cos60/2
Kc = cos30°
Kc = √3/2
Neon-lamp holders A lot of industrial electronic equipment uses neon lamps to indicate when they have been energized from the mains. If the lamp fails to glow, it means something is wrong with the supply circuit, the equipment, or the indicator itself. The neon lamps used are quite small and housed in holders 5 mm to 10 mm in diameter.
Regenerative braking occurs whenever the speed of the motor is more than that of the synchronous speed. In this method, the motor runs as a generator, and the load is used to provide the required power to the supply. The main criterion for regenerative braking is that the speed of the motor becomes greater than the synchronous speed. This condition will lead to the motor acting as a generator and the direction of both the current and torque reversing. This method can be utilized where the load on the motor has very high inertia.
When the applied voltage to the motor is less than the back electromotive force (EMF), then both the armature current as well as armature torque reverses and the speed reduces. As generated EMF exceeds the applied voltage, the power transport takes place from the load to the supply.
A phase sequence is an order or sequence in which the currents or voltages of different phases attain their maximum values. In a three-phase system, there are only two possible phase sequences: R-Y-B (positive Phase Sequence) and R-B-Y (Negative Phase Sequence).