Team Rush

Background
Transformers are a vital and expensive element in the power system. Damage to and disruption of a transformer can lead to an unplanned outage that can cost a utility millions of dollars. Thus, it is very important to limit any factors that might harm or disrupt a transformers operation. One of the major destructive forces is current inrush. Inrush occurs when a transformer is re-energized after a loss of power and is a product of several causes. These causes include system impedance, residual flux, and most critically the point at which the transformer is switched in.  

When power is restored to a transformer, the point at which each phase is closed in to the voltage waveform is not currently controllable. If energized at an un-desirable (near zero crossing) point in the waveform, the magnetizing voltage can push the core flux into saturation creating peak currents four to six times the steady state current.  This excessive current will not only overheat the windings of the transformer, but it also creates a physical force or torque within the windings that can do more damage than the overheating. These factors combined can lead to internal faults within the transformer. Our project intends to limit inrush current by controlling the point in the voltage waveform in which the transformer is switched in.
           
Project Outcomes
The primary objective of this project is to develop a bank of switches that are capable of energizing a single phase, then based upon proven design, all three phases of a transformer at any point in the voltage waveform. This will be accomplished by developing a microprocessor driven, power electronics (SCR) switch that will be capable of achieving the timing and accuracy necessary to close in at any desired point unique to each phase.

Need
A bank of power electronics switches capable of energizing each of the three phases of a transformer at any point in the voltage waveform unique to each phase.

Specifications

• Microprocessor Control for timing flexibility/optimization & future expansion
• Switches that can withstand 400 A peak current
• Must be capable of switching three phases
• Zero detection circuit that monitors a 240V 60 Hz signal
• System timing/propagation accuracy must be within 500μs
• Must keep track of voltage waveform for residual flux calculations

              
Constraints

• Budget not to exceed $3,000.00