Each locomotive carries 2 real boxes enclosing the static auxiliary converter system: BOX1 (containing BUR1) and BOX2 (containing BUR2, BUR3, and the battery charger — the charger is fed from one of the two converters and may be considered a functional part of the converter system). Three auxiliary converters connect to the main transformer's auxiliary-services winding; each is rated 100 kVA output with short-circuit-proof 3-phase output at 415V. BUR1/BUR2 give variable output frequency (0-50Hz); BUR3 gives fixed 50Hz output.
The battery charger is supplied from BUR3; if BUR3 has a fault, BUR2 feeds the battery charger instead. Rated output approx. 111V, the charger charges the loco batteries and supplies low-voltage loads — its low-voltage output is electrically insulated from both the input and the 3-phase output. Converters use external forced-convection cooling (approx. 5 m/sec); internal thermostats run the fans once temperature exceeds 50°C, until it drops below 35°C. Both boxes and the 3-phase output chokes mount in the machine room; the intermediate chokes are built into the main transformer tank itself, for convenience and weight saving.
Real Technical Data — Full Ratings
| Section | Parameter | Real Value |
|---|---|---|
| Input | Supply voltage | 1000V AC +200V/−300V |
| Input | Apparent power | 100 kVA |
| Input | Current (rms) | 150A (at 100kVA, 700V) |
| Input | Frequency | 50Hz ± 3% |
| Input | Rated insulation voltage | 1200V |
| Input | Test voltage (50Hz/60 sec) | 4250V |
| Intermediate circuit | Voltage | 550 VDC |
| Intermediate circuit | Rated current | 155 ADC |
| Intermediate circuit | Short-term overload | 190 ADC |
| Intermediate circuit | Rated insulation voltage (capacitor) | 900V |
| Intermediate circuit | Test voltage (50Hz/60 sec) | 2600V |
| Output — AC | Rated voltage (fundamental rms) | 415V |
| Output — DC | DC voltage | 111V |
| Output — AC | Rated frequency (BUR1&2 / BUR3) | 50Hz / 50Hz |
| Output — AC | Rated current (incl. battery charger) | 140A |
| Output — DC | Max. battery-charger current (battery only) | 80A |
| Output — DC | Max. battery-charger current (user + battery) | 110A |
| Output — AC/DC | No. of poles (conductors) | 3 / 3 |
| Output — AC/DC | Rated insulation voltage | 900V / 150V |
| Output — AC/DC | Test voltage (50Hz/60 sec) | 2600V / 1500V |
| Control unit | Supply voltage (operating range) | 77...137.5V |
| Control unit | Power consumption | 120W |
| Thermal | Losses at rated power, Box1 | 2 kW |
| Thermal | Losses at rated power, Box2 | 5 kW |
| Thermal | Ventilator supply voltage | 36...56V |
| Thermal | Ventilator power losses | 5W |
| Thermal | Air rate | 5 m/sec |
Real Circuit Description & Main Parts
Main converter parts: a half-controlled rectifier bridge, an intermediate filter (inductor + capacitor), three inverter legs connected as a 3-phase inverter, an electronic control unit, a 3-phase output inductor, and the battery charger (a 3-phase transformer + rectifier). Other components detect actual values needed to control the process and maintain reliable power-electronics operation.
- Rectifier: a half-controlled asymmetrical-type GTO rectifier converts AC to DC, maintaining output DC voltage of approx. 550V. Average rectifier output voltage: U2 = (√2/π) × Un(rms) × (1+cos α), where α is the thyristor firing/control angle. Active power transmitted: P = UZ × IZ (IZ = average link-filter current).
- DC-link filter: the intermediate-circuit reactor smooths pulsating energy flow from the input rectifier, supplying DC current (IZ) with superposed ripple; the choke has 2 coils to keep voltage spikes away from the inverter and load. The intermediate-circuit capacitor (CZ) absorbs the current component with little terminal-voltage fluctuation, represents the low-impedance voltage source essential for the 3-phase inverter, and supplies magnetisation current to the inductive load. Real construction: CZ consists of a 2-stage series circuit of 6 parallel-connected electrolytic capacitors each; series-stage voltage is balanced with resistors sized so their current is several times the capacitor leakage current (they also double as discharge resistors).
- Three-phase inverter: 3 single-phase inverter modules generate 3-phase AC from the DC-link voltage by approximate ON/OFF switching. Rectangular inverter output voltage represented as an infinite sine sum: U(t) = UZ × [(√6×√2)/(π×n)] × Σ sin(n×2πf1×t), where f1 is inverter fundamental frequency and n = 1,5,7,11,13,17...(= 6k±1, k=1,2,3,4...). Shaft power of the motor is a function of the fundamental component U1rms = UZ×(√2/π). For resistive loads, heating is a function of total rms value: V(total rms) = UZ×√(2/3). In steady state, both output frequency and amplitude match the set point; in dynamic conditions these can be set away from reference by PWM for better process control.
- 3-phase inductors: slightly attenuate harmonics, but mainly give the converter the required capability of withstanding load short-circuits.
- Battery charger: diode bridge (real tag 107) rectifies voltage supplied from one of the auxiliary inverters through a 3-phase transformer (real tag 107.1). A 2.2 mF capacitor on 107 smooths charger voltage and limits transient voltage rise when a major load switches off. Current transducers 107.2/107.3 transmit actual current values to BUR2's control unit, while transducers on the charger module transmit the same to BUR3's control unit (BUR3 normally supplies the battery charger).
Real Protective & Measurement Devices
- Battery charger circuit breaker [100]: protects against overload by magnetic tripping, isolating the charger from inverter output on internal short-circuit — the converter needn't switch off and the loco can keep running until battery capacity is exhausted.
- Input fuse [40]: protects from serious consequential damage from power-component failure in the rectifier bridge or regulation/monitoring defects.
- Surge arresters [40.1]: protect rectifier-bridge [50.11] semiconductors from over-voltage spikes.
- Damping filter RC [49.2/49.1]: a small filter limiting the rate of rise of voltage spikes, avoiding spurious thyristor firing.
- Real measurement devices: (I) input voltage measuring transformer — gives the electronic control unit amplitude/phase information on the input; (II) voltage transducer — measures intermediate-circuit voltage.
Auxiliary Converter Control Unit — Real Rack Contents
The control unit handles all control and electronic-protection functions, communicating with the vehicle control unit (FLG) via the MVB optical bus.
- A power pack, electrically insulated between input and outputs, converting battery voltage (which varies over a wide range) into stabilised voltages: ±24V for gate-unit supply, ±15V for analog circuits/transducer supply, and ±5V for digital circuits — all sharing a common ground.
- The microprocessor unit (with binary I/O card): regulates link voltage (controlling the input rectifier) and battery voltage; handles higher-level protective functions, contactor control, and FLG communication.
- The bus interface board: converts electrical signals from the microprocessor unit into optical ones, and vice versa.