Full features of servo stabilizer

Servo stabilizer is a very useful and highly effective equipment used to maintain constant electricity supply. Suddenly power fluctuation is a common problem especially in India,  power fluctuation can damage machinery which is operating with electricity. The crucial solution to keep this machinery safe is to use a Servo voltage stabilizer.

The schematic diagram of the servo is given in the figure below. It consists of

1. Step-less variable toroidal wound a motor-driven auto-transformer also known as dimmer-stat or variac.
2. Reversible, instantaneous start synchronous motor (Servo motor)
3. Buck-boost transformer (Series transformer)
4. Power contactor
5. Electronic control system
6. Metering and indication panel
7. Protection and cutoff system ( if any)
8. Housing suitable for air/oil cooling.

The buck-boost transformer is a series of control transformer interposed between input and output. The primary is fed through the Autotransformer output. Depending upon the variation in the input voltage variation, a voltage is induced in this transformer in-phase or out of phase with reference to the input voltage so as to regulate the voltage at a steady value. Thus both step up and step down voltages are obtained through the same transformer tapping. The electronic control system monitors the output voltage continuously and based on the variation of output voltage the servo motor is driven in the forward and reverse direction to vary the output of the Autotransformer which in turn changes the voltage compensation at the buck/boost transformers. The control system monitors the voltage between the phase and neutral for each phase and regulates the voltage on each phase. However, the regulation of voltages between the phases may be slightly different based on the actual loading of the individual phases.

The single-phase stabilizer employs one variable Autotransformer driven by a servo motor and one sensing circuit.

The balanced type three-phase stabilizer also employs a single control circuit. Here the three variable autotransformers are mechanically coupled and are driven by a single motor. The sensing is done in one of the three phases and the other two are corrected automatically. These stabilizers can be used with loads where unbalance is not much and lesser accuracy in output is acceptable.

For the unbalanced load and unequal input voltages, the three phase servo voltage stabilizer consists of three sets of identical components each set corresponding to a single phase system with the corresponding control system and with a common output contactor housed in the same enclosure for smaller capacities and in separate enclosure for very high ratings. The main electrical systems are connected in Star to form a three phase system with a common neutral between input and output. In case of oil cooled system, the Auto transformer and buck-boost transformers are immersed in oil.

Full features of Servo Stabilizer

Simple creation and functionality - These devices are construction with a simple structure consisting of a variable transformer, ac synchronous motor, transistor, comparator, simple electronic sensing circuit and impulse transformer. Servo Voltage stabilizer manufacturers design these machines with extremely simple operating principle that a user can easily understand.

Slighter deformation in the output waveform - Less number of relays as compare to other range of stabilizers, brings down switching and in result decreases the time delays. Another feature here is less or almost no dropping in connection due to continuous regulation of output voltage by the variac.

Use of analog electronic course - In servo control voltage stabilizers, the analog electronic circuit is used in the control circuit. Voltage comparator in the circuit makes it less complicated and easily understandable.

Suitable for large loads - These devices make a perfect choice for the appliances with requirement of large loads at the output. This is made possible by the large power and current handling capacity of the voltage stabilizer. Manufacturer and suppliers, generally suggest these stabilizers in the units with large loads.

Cost effectiveness and loss control - Sudden power cuts and fluctuations can result in different costs including machine repair and management cost as well as decreased productivity due to machine breakdown. These stabilizers put a check on the negative impact of irregular current flow and prevent the industrialists from different losses.

Other features - These stabilizers can be adjusted in minimum space and can work well in different conditions. Besides protecting the machines, these also work as a protection shield for the employees and protect them from sparking and other accidents.

OPTIONAL FEATURES: 

1. Reverse phase protection.
2. By pass arrangement to connect the output directly to the input in case of failure of the stabilizer.
3. Line filter for suppressing the radio frequency components.
4. Surge suppressor to suppress the voltage spikes.

FAILURE OF THE STABILIZER: 
The main failure of the Servo stabilizer occurs on account of Auto transformer and the servo motor. So they should be of the reputed makes. The selection of variac with the proper rating plays an important role in the satisfactory performance of the stabilizer. It is advisable to derate the name plate rating by 10 to 15 % for air cooled systems, as many stabilizers fail on account of the failure of the variac operating under the adverse condition of very low input voltage and high load current.