AVSR3 Triple Switch Autocalibrating Variable Step Power Factor Regulator

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The AVSR3 employs our variable step technology to compensate reactive current in seven steps. It features three 25 A solid state switches to connect three autodetected compensating capacitor banks in and out of the single- or three- phase line system. At installation no adjustments are required as each capacitor size and all other operation parameters are detected automatically making AVSR3 commissioning purely "wire-up-and-play".
 

AVSR3 Autocalibrating variable step PF regulator

The variable step technology provides for different capacitor banks of any size to correct power factor in practically any arbitary minimum step and correction range size. At every sampling instant, the controller calculates the required compensation step and connects or disconnects a combination of banks whose sum is equal or closest to the calculated step value. In the AVSR3, three banks are used and, if sized as x1, x2 and x4 multiples of the smallest required step, provide seven steps of compensating operation. Switch activation/deactivation happens at every sampling instant as set at the DIP switch between 5 and 30 seconds. The AVSR3 response time range makes it particularly suitable for dynamic power factor compensation of frequently started, low-duty or variable loads such as: Lifts, Conveyors, Compressors, Pumps, Fans, and Office lighting. Each capacitor bank size is autodetected during AVSR3 installation. The unit features a selfcalibrating function during which the AVSR3 corrects all internal errors and offsets, measures the current transformer phase shift and the individual capacitor bank sizes. The measured parameters are then used during normal operation ensuring accurate, effective and dependable performance. Following autocalibration no other adjustment is required making AVSR3 installation fast and error-free.

The AVSR3 is highly integrated and adaptable to all power factor capacitor compensation applications. The only other parts required to build a complete power factor correction system are the current transformer, the compensating capacitors and their protective fuses.

The AVSR3 is designed for standard European and US, single- and three-phase, 50-60 Hz lines. Characterizing features are as follows:

• Variable compensating capacitance step is any combination of the three driven banks, effectively realizing an up to 7 step system
• Autocalibration function corrects all errors and detects the current transformer phase shift and each capacitor bank size. No other adjustment or rewiring is needed.
• Separate, galvanically isolated control supply terminals can be connected directly to the line or a separate control power line.
• Enabling bit I/O pair allows for integration in a supervisory system or connection to an external master. The input interfaces to a NPN (current sink) external control source or enabling signal. It is internally connected to the isolated internal interface power supply and is protected against overvoltage transients. The output consists of an uncommitted 24 VDC optotransistor which is protected against overvoltage transients and is isolated from all other AVSR3 supply potentials. Alternative, DIP switch selectable operation modes allow for tandem and interlock external control.
• The enabling bit I/O pair allows for the following DIP switch selectable operation modes:
  • Standard or static mode: Operation is enabled by the “Enable” input and reported by the “Ready” output.
  • Tandem mode: A number of AVSR3s are connected in tandem (ie each “Ready” output driving the “Enable” input of the next unit) to realize systems with more capacitor banks. Group control is effected via the “Enable” input of the first unit.
  • Interlock mode: A number of AVSR3s are connected in a ring (ie each “Ready” output driving the “Enable” input of the next unit in the ring) allowing for only one bank of the group to switch in/out. Used typically with single phase AVSR3s controlling the individual phases of a three phase load to minimize line disturbances when connected to a weak neutral. Group control is effected via a series switch in one of the “Enable” input.
• Current detection is effected by standard 5 A secondary current transformer (CT). The transformer phase shift is detected at autocalibration and, as such, the CT can be placed in any of the phase lines and in random direction.
• The reactive current is detected by measuring the current phase and magnitude.
• Solid state circuits switch each 25 A compensating capacitor in and out of the line at every sampling instant. Each circuit is protected against overheating, typically caused by the eventual bypass relay failure.
• Zero crossing type switches ensure that the capacitors are switched in when the line voltage equals their voltage resulting in very "quiet" operation. Capacitor inrush currents and the associated generation of harmonics and ringing are eliminated and capacitor life is extended and safeguarded.
• Bypass relays are employed across each solid state switch to minimize switch losses. Their eventual wear-out will be detected by the power circuit overheat protection sensor.
• DIP switch selectable sampling time of 5, 10, 20 and 30 seconds.
• DIP switch selectable forced state turns each switch on or off regardless of current input enabling individual power circuit testing.
• 2x16 character LCD display shows system state, variable and error messages in user readable and friendly format.
• Isolated control circuit enhances safety and noise immunity.
• Protection against line overvoltages, faults and power circuit overheating.

During normal operation the AVSR3 display indicates system status, error conditions (such as out-of-range line frequency or an overheated switch) and variables such as load/line power factor and power, percentage capacity switched-in and switch state. In the event of a power circuit overheating, the failing switch and the "Ready" output are deactivated until power is removed. Overheating is usually the result of switch bypass relay failure and, more rarely, thyristor short failure.

The controller can be programmed, configured and monitored by computer using the USB/TTL interface and the provided avsr3_jobs software, downloaded from here (760K, zip archive).

Our power factor related products are summarized here with sampling/small quantities being available for online purchase here.

 

Assembled, ready-to-install power factor correction systems in wall mountable or free standing cabinets are available on a custom basis.