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MD Series (3.1kVA - 7.5kVA)

The MD Series is a single phase, seamless transfer, uninterruptible power system providing premium power to various types of loads ranging from industrial to information technology. The overall function of the MD Series is to take polluted, fluctuating, and erratic electrical power that exists in all areas and purify it, resulting in well-regulated, clean, uninterrupted, computer-grade power. Up to 18 minutes of internal battery backup is provided, model-dependent, with external battery options available providing several hours of runtime at full load.


  • Networking LAN/WAN
  • Hosts/Hubs
  • Information Technology
  • Telecommunications
  • Industrial Controls
  • Medical Labs
  • Communication Closets
  • Voicemail Systems

Product Specifications

Features and Benefits

  • Steady Regulated Voltage to +/- 3%
  • 100% Power Conditioning
  • No-Break Continuous Power Providing Seamless Switching to Battery
  • Field Expandable Power Rating and Battery Run Time
  • 94% Efficiency
  • Computer Grade Electrical Isolation
  • Switch Mode Rated
  • Internal Bypass Option that “Maintains System Isolation and Voltage Transformation” when in Bypass Mode
  • Optional NetMinder Ethernet/MODBUS Adapter for Remote Monitoring

Performance Specs

  • Voltage Regulation: +/3%
  • Load Regulation: typically better than +/- 3%
  • Overload Capability: 125% for 10 min
  • Surge Capability: 150% of rated output
  • Input Operating Range: +10 to -40% (typical)
  • Input Current THD: < 10%
  • K-Factor: 30 or better
  • Operating Temperature: 0°C to 40°C
  • Common Mode Noise Attenuation: 120dB
  • Transverse Mode (Line) Noise Attenuation: 70dB
  • Spike Attenuation 3000:1
  • Crest Factor 3.5:1

Single Phase Sizes

  • 3.1kVA, 3.5kVA, 4.5kVA, 5.0kVA, 6.0kVA, 7.0kVA, 7.5kVA

Frequently Asked Questions

Is the MD a standby UPS?

No. The MD uses a seamless ferroresonant transfer system to secure optimum performance. Unlike standby systems that do nothing until power fails, the MD conditions, regulates, and filters the power 100% of the time. The load receives a steady, spike-free, sine wave voltage regardless if the incoming power is in or out of acceptable range.

How does the MD regulate voltage?

The MD incorporates a highly efficient ferroresonant transformer that produces a steady output voltage over a wide range of input voltages. Even in severe brownout conditions, the MD delivers regulated voltage to within +/-3% without using battery power.

How does the MD correct for bad power?

The ferroresonant transformer remains in the power circuit 100% of the time. Since the transformer is designed to pass only 60Hz, the power distortion of other frequencies will not be present in the output. The MD corrects for bad input voltage waveforms with distortion levels as high as 40%. Most standby UPS units will not tolerate over 7% distortion, they switch to battery backup. The MD preserves the battery power for only outages.

What level of TVSS (surge) protection is offered by the MD?

The limited protection that a standby UPS offers is from its TVSS circuit. The typical TVSS protection is no more than a couple of dime- to nickel-sized metal oxide varistors (MOVs), offering limited and temporary protection. In contrast, the MD protects the load with 100 pounds or better of pure transformer steel. The transformer absorbs the high energy transients leaving the load solidly protected. In addition, it also replenishes the energy where notching and reverse spiking occur.

Is it true that the MD improves the operation of equipment connected to it?

Yes. The output filter circuit removes unwanted frequencies generated by non-linear loads. This characteristic lowers the high load current demand and improves the power factor. The load feels gentler currents and produces much less heat, increasing its efficiency and extending its life.

How does the MD correct for ground noise, when other UPS’s of similar VA sizes do not?

The MD uses a high level isolation ferroresonant transformer for power conditioning. Only an isolation transformer removes common mode noise (the noise generated on the ground lead). Most other uninterruptible power systems use an auto transformer for some voltage correction functions and ignore the need for common mode noise attenuation.

How does the MD correct for improper site wiring?

Site wiring is always an unknown. There may be voltage variations, ground current that causes disruptive operation (unsolvable with TVSS), mixed grounds, etc. The MD’s ferroresonant transformer generates the equivalent of a new power source dedicated to the load. It creates a new clean ground reference and establishes a central ground point for all loads. The new ground assures that data spike attenuation networks are at the most optimal location (the shortest lead length to ground).

How does the MD provide superior isolation compared to typical units of the same size?

Most standby UPS systems just pass the incoming power directly to the load without any regulation, power conditioning, and/or isolation. The MD uses a special ferroresonant isolation transformer for power purification and isolation.

Does the MD do anything to correct for load-generated harmonics?

Yes. The MD’s ferroresonant transformer acts as a band pass filter, allowing only 60 cycles to pass. Load generated noise and harmonics are trapped in the output of the MD, preventing the unwanted harmonics from reaching the input power source. Standby uninterruptible power systems simply don’t do anything for harmonics; you live with the results.

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