So why do synchronous motors offer such significant and speedy savings?
Essentially it’s thanks to the motor’s ability to reduce electrical energy costs, and improve energy efficiency, by correcting power factor on the motor power supply. In addition, they provide high torques and constant speed under load variation, which results in low operating and low maintenance costs.
These benefits explain the use of the motors in a wide range of industries, including mining and quarrying, steel, pulp and paper, wood processing, sewage, chemicals and petrochemicals, cement and oil. Applications in these industries include crushers, mills and conveyor belts; fans, pumps and compressors; pulp and paper extruders; wood chippers and debarkers; and fans and water injection pumps.
Less stress, more efficiency
Due to their higher efficiency level, reduced size and higher output rating, synchronous motors can replace DC motors in high-performance applications. In addition, in a number of instances, a motor with lower torque values compared to standard can be applied. This brings a positive reduction in motor starting current – resulting in fewer problems with the electric system during starting – together with a reduction of mechanical stresses from the motor windings.
Although synchronous motors have better efficiency and speed accuracy than induction motors, their design is more complex. This means that cost comparisons between the two are not entirely straightforward.
The simpler design of the induction motor makes them less expensive for a given power level, at power outputs up to 10 megawatts. But above this figure, the higher efficiency of synchronous motors delivers lower operating costs.
This higher efficiency is the result of synchronous motors’ superiority at converting electrical energy into mechanical power. They can also be designed for high efficiency operation across a broad speed range, which in turn provides significant energy-saving across a wide variety of loads. And for applications requiring high torque – such as crushers, extruders and so on – breakdown torque with synchronous motors can be as much as five times higher than the rated torque.
An additional benefit of synchronous motors is their ability to improve stability in Variable Frequency Drive (VFD ) applications.
Synchronous motors with variable speed are recommended for applications with high torque, low speed and wide speed adjusting range. Depending on load and environment characteristics, motors for such applications can be constructed with or without brushes. These motors are suitable to operate at any speed range from zero to maximum, and will maintain stability independent of load variation, which – on equipment such as laminators, plastic extruders and similar – is a capability of paramount importance.
Maintenance not missed
On brushless-type machines, the reductions in day-to-day running costs delivered by synchronous motors are complemented by reduced maintenance costs. Since the motors are manufactured without brushes or slip rings, obviously the usual inspection, cleaning or other maintenance of these components is not required.
Synchronous motors require a DC power supply to power the field winding (rotor winding). This comes from a brushless rotating exciter (on brushless versions), or via a static exciter on versions with brushes. WEG synchronous motors supplied with static exciters are fitted with slip rings and brushes that allow current powering of the rotor poles through slipping contacts. The DC power supply for the poles is derived from an AC /DC converter and static controller. The static exciter is used extensively on VFD applications.
WEG synchronous motors with a brushless excitation system are fitted with a rotating exciter, normally installed on the rear of the motor. Depending on motor operation, the exciter has either a DC or AC power supply on the stator.
The safe choice
WEG design and manufacture synchronous motors in sizes up to 20MW for general industrial applications, and also offer versions for hazardous (flammable) atmospheres both on- and off-shore.
These hazardous area motors are supplied in a range of protection levels, such as Ex-n (non-sparking) and Ex-p (pressurised), to meet national and international standard requirements.
In addition, these WEG synchronous motors are tested and approved by worldwide certifying institutions including API, NEMA , IEC , CSA, BVQI, NBR, ABS and DN V.
So if you’re looking for high efficiency, speed accuracy, and fast payback, a WEG synchronous motor is your safe choice – in more ways than one.