In industries, induction motors are more popular and widely used. Especially Squirrel Cage Induction motor is used for various industrial drives and loads due to its rugged design and less maintenance requirement. Synchronous motor applications are not so popular due to requirement separate field excitation source, auxiliaries for starting and control devices. These make it expensive to use as compared to low cost induction 3 phase induction motors. However, there are some industrial applications which demand the use of synchronous motor.
Synchronous motor applications are required where a precise speed or position control is needed. It is more suited for constant torque and constant speed drives. Unlike 3 phase induction motor, synchronous motors can be designed for required torque, power factor and starting VA requirement to suit a particular need. This is the reason; it is widely used in paper and pulp industries.
Synchronous Motors are basically used for the following applications:
- Power Factor Correction
- Voltage Regulation
- Constant Torque and constant Speed Drive
Synchronous Motor Applications:
- Synchronous motor is used as synchronous condenser for power factor correction or improvement. Synchronous condenser is an over-excited synchronous motor without having any mechanical load connected to its shaft. A synchronous condenser when connected to supply mains takes leading current and hence delivers the reactive power. This reactive power delivered by the synchronous condenser is absorbed by the connected induction motors and thus the supply line is relieved from carrying reactive power. In this way, the overall power factor is improved. Use of synchronous condenser for power factor improvement is advantageous as the amount of reactive power generation can varied by the adjustment of field excitation. This is not possible with static capacitors. For detail, please read “How Synchronous Motor Improves the Power Factor?”
- It is used at the end of transmission line for voltage regulation. Though this method is obsolete now and various electronic devices like STATCOM are employed for this purpose.
- Due to higher efficiency as compared to 3 phase induction motor and constant speed irrespective of load variation, it is used for constant speed drives. Some typical applications of synchronous motor are in compressor motor in Oil & Gas industry, centrifugal pumps, reciprocating pumps etc.
- A synchronous motor is also used in household applications. It is used in microwave oven, clock, tape players etc. In microwave oven, it is used to rotate the turn table.