Biomedical
Triplen harmonic filter's stellar performance eliminates high neutral current & ensures electrical fire safety of biomedical equipment in hospital building. Almost regularly we read in newspaper about electrical fire incident happening in hospital buildings and in ICU blocks. Every ICU bed utilizes a medical pendant. It supplies medical gases like oxygen and air to ventilator, and ups power to patient monitor and ECG machine. It also supplies raw power for bed position control. Together it consumes up to 3A in phase current from the UPS power supply. It consists 33% harmonic current. That adds up and trebles at the neutral and produces a 3A high frequency harmonic current in the neutral conductor. It comprises of 3rd (150Hz current), 9th (450hz current) and 15th (750hz current) harmonics which are odd multiples of three. Thus they are referred to as triplen harmonic currents.
Hospitals routinely report maloperation and failure with biomedical equipment. The most reported problems are due to electronic-card-failures like in motherboard-failure, monitor-failure, hard-disk-failure and SMPS-failure with ICU patient monitor, dialysis equipment, cardiac-ACT-machine, X-ray machine, blood bank defreeze and minimum-invasive-surgery equipment. In-addition controller card fails with MRI, CT-Scan and Cathlab equipment.
Hospital buildings are increasingly replacing incandescent lamps and fluorescent lamps with LED light. This is to reduce energy consumption and achieve green building norm. Light emitting diodes do not contain hazardous toxic substance like mercury. But LED drivers are a switching device. It generates harmonic current and causes electromagnetic interference (EMI) in building's electrical power system. It creates a significant percentage of triplen harmonic current into the hospital's power supply.
In a Case Study with Biomedical equipment the power and harmonic measurement was done before and after installation of triplen harmonic filter. UPS powers hospital's biomedical equipment which generates triplen harmonic current. It then enters the UPS power supply. Both the lines and the neutral of the UPS output supply thus contain triplen harmonic current. A 2nos 250kva UPS in parallel was supplying to the hospital's biomedical, IT-server and computer loads. UPS output power distribution was done through floor-wise and section-wise UPS DBs. A triplen harmonic filter of 10A/phase and 20A/neutral specification was installed at a "Floor UPS DB".
1. Before installation of triplen-filter the current and triplen-current-harmonic in that "Floor UPS DB" at R-Y-B-N phases were 27.0- 3.8- 4.0- 24.0 Amps and 20.0%- 25.0%- 12.1%- 30.6% respectively. The lines to neutral voltages in R-Y-B phases were 230- 229- 229 volts. The current unbalance was 133% (15.4/11.6) x100%. The unbalance is calculated by the maximum deviation (27.0- 11.6) from its average current (11.6).
2. After installation of triplen-filter the current and triplen-current-harmonic in that "Floor UPS DB" at R-Y-B-N phases were 16.0- 10.0- 9.5- 3.1 Amps and 6.6%- 9.5%- 9.7%- 11.2% respectively. The line to neutral voltages in R-Y-B phases were 230- 230- 230 volts. The current unbalance was 35% (4.17/11.8) x100%.
3. Neutral Current reduced by 87% [(24.0- 3.1)/ 24.0)]
4. Neutral Triplen-Harmonic-Current reduced by 95% [(24x0.306 - 3.1x0.112)/ 24x0.306]
5. Unbalance Current reduced from 133% (greatly unbalanced) to 35% (mostly balanced).
In a Case Study with LED Light the power and harmonic measurement was done before and after installation of triplen harmonic filter. A 1000KVA, 11/0.433kV, 50hz transformer was supplying to building's total load that including LED lights. Lighting distribution was done through floor-wise and section-wise LDBs. A triplen harmonic filter of 10A/phase and 20A/neutral specification was installed at a "Floor LDB".
1. Before installation of triplen-filter the current and triplen-current-harmonic in that "Floor LDB" at R-Y-B-N phases were 10.8- 15.9- 17.9- 11.0 Amps and 27.1%- 12.4%- 13.1%- 30.0% respectively. The line to neutral voltages in R-Y-B phases were 231- 230- 232 volts. The current unbalance was 27% (4.06/14.86) x100%. The unbalance is calculated by the maximum deviation (14.86- 10.8) from its average current (14.86).
2. After installation of triplen filter the current and triplen-current-harmonic in that "Floor LDB" at R-Y-B-N phases were 10.8- 11.4- 15.4- 1.7 Amps and 15.5%- 8.1%- 8.3%- 12.5% respectively. The rated lines to neutral voltages in R-Y-B phases were 240- 240- 240 volts. The current unbalance was (2.87/12.53) x100%, which is 23%.
3. Neutral Current reduced by 85% [(11.0- 1.7)/ 11.0)]
4. Neutral Triplen-Harmonic-Current reduced by 94% [(11.0x0.30 - 1.7x0.125)/ 11x0.30]
5. Unbalance Current reduced from 27% (mostly balanced) to 23% (still better)
6. The client has confirmed elimination of LED driver failure.
7. The client has confirmed achieving good energy saving.
