Application

Medha's 3 Phase AC motors with built-in inverters are designed using a DSP (Digital Signal Processor) for control and IGBT semiconductor power devices in inverter. These AC Motor-Inverter combinations are a good retrofit alternative for failure prone and high maintenance DC Motors used for the same functions in older locomotives. The Inverter takes DC supply from locomotive batteries and provides required sinusoidal supply to 3-phase AC motors.

Three types of motors are used for different functions in the locomotive.

1. 1.5 HP Fuel Pump Motor with pump.
2. 0.87 HP Dust Exhauster Blower Motor with blower.
3. 0.5 HP Crank Case Blower Motor with blower.

These inverter motors are protected for input under voltage, input over voltage, output overload, output short circuit, input reverse polarity, over temperature. Surge protection as per IEC 571.
Inverter module is divided into two sections.

1.Booster section:
It is used to generate stable DC link voltage for PWM inverter, which is independent of input voltage variations. The switching element of the Booster circuit consists of MOSFET module. All features of booster are monitored and controlled through DSP.

2.Inverter section:
It uses three half bridge IGBT phase modules and a DSP control card. DSP controller circuit generates the inverter PWM signal for IGBTs to synthesize a Sine Weighted PWM voltage with required output frequency. The control card is responsible for overall system control through status monitoring, diagnostics and PWM waveform generation for inverter.