Spring Creek Road, Dunollie, West Coast. Solid energy spring creek mine. Solid Energy: Closed mine not another Pike. Published: 5:16AM Tuesday February 21, 2012 Source: ONE News State-owned Solid Energy says workers at its Spring Creek mine were never in danger despite the mine being closed because of safety concerns. The Department of Labour shut down the mine, about 10km outside of Greymouth, after three incidents in the last two weeks. ONE News understands at least one Solid Energy employee is now under investigation. The Labour Department says a diesel generator caught fire, injecting deadly carbon monoxide into the coalmine, where 40 men work underground, and ventilation fans in the mine stopped working. Solid Energy's chief operating officer Barry Bragg said he was "very unhappy" about the repeat incidents, which he blamed on faulty engineering. But he said he was confident there would not be a repeat of the Pike River explosions at Spring Creek.
"We are confident, but we're not happy that these events occurred, and it's our responsibility to fix the problems," Bragg said. Reporting error More scrutiny. Commission Hearings - pikeriver.royalcommission.govt.nz. Phases There are four phases to the Pike River Royal Commission’s inquiries and the Commission will hold public hearings in relation to each of them: Phase One: ContextPhase Two: Search and RescuePhase Three: What happened at Pike RiverPhase Four: Policy Aspects Timetable The timetable for the Pike River Royal Commission hearings is as follows: Phase One – Context Date of hearing: 11 July - 22 July 2011 Date evidence to be received by the Commission: Evidence relating to issues 1.1 to 1.6 and 1.13 to 1.18: No later than 6 May 2011Evidence relating to issues 1.7 to 1.12: No later than 3 June 2011 Phase Two – Search and Rescue Date of hearing: 5 September - 23 September 2011 Date evidence to be received by the Commission: No later than 1 July 2011 Phase Three – What Happened at Pike River?
Date of hearing: 14 November - 25 November 2011 Date of hearing: 5 December - 9 December 2011 Date of hearing: 8 February - 17 February 2012 Phase Four – Policy Aspects Hearing Plans - Witness Lists Live Streaming. What is a Variable Frequency Drive (VFD)? How Does a VFD Work? (Part 2) What is a VFD? (Part 1) By: Dave Polka Part 2 How Drive Changes Motor Speed Just how does a drive provide the frequency and voltage output necessary to change the speed of a motor?
That's what we'll look at next. Figure 6, Basic PWM Drive Components Although some drives accept single-phase input power, we'll focus on the 3-phase drive. Switching Bus With IGBTs Today's inverters use Insulated Gate Bipolar Transistors (IGBTs) to switch the DC bus on and off at specific intervals.
Figure 7, Drive Output Waveform The drive's control board signals the power device's control circuits to turn "on" the waveform positive half or negative half of the power device. Figure 8, Drive Output Waveform Components The speed at which power devices switch on and off is the carrier frequency, also known as the switch frequency. Shrinking cost and size Drives vary in the complexity of their designs, but the designs continue to improve. Sidebar: What if you have SCRs? Technical Guide to Harmonics with AC Drives.
Contents General This guide continues ABB's technical guide series, describing harmonic distortion, its sources and effects, and also distortion calculation and evaluation. Special attention has been given to the methods for reducing harmonics with AC drives. Basics of the harmonics phenomena Harmonic currents and voltages are created by non-linear loads connected on the power distribution system. Harmonic distortion is a form of pollution in the electric plant that can cause problems if the sum of the harmonic currents increases above certain limits. All power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the grid. Figure 2.1 Plant with converter load, mains transformer and other loads. The line current of a 3-phase, 6-pulse rectifier can be calculated from the direct output current by using the following formula.
The fundamental current is then The rms values of the harmonic components are: Pub-119-earthing-practice.pdf. Zambian earthing. Neutral%20Earthing%20Resistors%20or%20Reactors%20Application%20Guide. Types of Neutral Earthing in Power Distribution « Electrical Notes & Articals. Types of Neutral Earthing in Power Distribution: Introduction: In the early power systems were mainly Neutral ungrounded due to the fact that the first ground fault did not require the tripping of the system.
An unscheduled shutdown on the first ground fault was particularly undesirable for continuous process industries. These power systems required ground detection systems, but locating the fault often proved difficult. Although achieving the initial goal, the ungrounded system provided no control of transient over-voltages.A capacitive coupling exists between the system conductors and ground in a typical distribution system. As a result, this series resonant L-C circuit can create over-voltages well in excess of line-to-line voltage when subjected to repetitive re-strikes of one phase to ground.
This in turn, reduces insulation life resulting in possible equipment failure.Neutral grounding systems are similar to fuses in that they do nothing until something in the system goes wrong. Nuetral voltage displacement - earthing. Resistance. Ground (electricity) A typical earthing electrode (left of gray pipe), consisting of a conductive rod driven into the ground, at a home in Australia. Many electrical codes specify that earthing wires must be a certain color, to mitigate wiring errors. In electrical engineering, ground or earth can refer to the reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
For measurement purposes, the Earth serves as a (reasonably) constant potential reference against which other potentials can be measured. An electrical ground system should have an appropriate current-carrying capability to serve as an adequate zero-voltage reference level. In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount of current without changing its potential. In a polyphase AC system, an artificial neutral grounding system may be used. Earthing bonding telecom installations. Power system design. Power line communication. Power-line communication (PLC) carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers.
It is also known as power-line carrier, power-line digital subscriber line (PDSL), mains communication, power-line telecommunications, or power-line networking (PLN). A wide range of power-line communication technologies are needed for different applications, ranging from home automation to Internet access which is often called broadband over power lines (BPL). Most PLC technologies limit themselves to one type of wires (such as premises wiring within a single building), but some can cross between two levels (for example, both the distribution network and premises wiring). Typically transformers prevent propagating the signal, which requires multiple technologies to form very large networks. Various data rates and frequencies are used in different situations. Basics[edit] Long haul, low frequency[edit]
Abb_technical_guide_no5_revc. Grd_AC-DC_Low_And_Med_Voltage_Drive_Sys.