Unisin 2100 Neutral Current Filter
Benefits for Gaming Machines
Application Note
May 2003

For electronic equipment and devices that are susceptible to malfunction caused by harmonic distortion, IEEE Standard 519 states that AC sources shall have no more than 5% total harmonic voltage distortion and no more than 3% for single harmonics for computers and allied equipment. Casino slot machines fall into this category. Furthermore, casino slot machines and other electronic devices in this category are very sensitive to neutral to ground voltage which can be very significant due to heavy currents in the neutral conductor, including zero sequence and other currents, of up to 3 times the fundamental power current

There are several possible remedies available of which the most effective appears to be the use of a grounding transformer filter, Unisin 2100, to bypass the high magnitude neutral current and reduce the neutral to ground voltage significantly by up to 90% or more, resulting in very low neutral current and very low neutral to ground voltage.

Experience has demonstrated significant proven benefits of utilizing grounding transformer filters for single-phase nonlinear loads, including:

  1. Ensured normal operation of connected loads. For casino slot machines particularly, abnormalities in the slot payout percentage are eliminated.
  2. Prevention of overheating and burnout of the distribution transformer
  3. Avoidance of neutral conductor overheating and therefore of the need to oversize the neutral conductor
  4. Improvement of system power factor
  5. Minimization of power loss in conductors and connected loads
  6. Reduction in voltage distortion
  7. Reusability of grounding transformer filters in successive facility renovations.

For Unisin documents available on the web, see http://www.unisin.com/
[1] “Harmonics in 3 Phase 4-Wire Systems”, Technical Bulletin TB103.1.

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© 2003 Unisin Power Technology
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