The Dynapower line of frequency converters utilizes the company’s proven expertise in power electronic rectifier and inverter systems. The incoming 480V, 60Hz, 3-phase voltage feed is rectified to an intermediate DC bus. A state-of-the-art inverter module inverts this DC voltage to the required 400Hz output.
At the input section, the converter is equipped with a three-phase circuit breaker for circuit protection. Control system and cooling power is sourced from the three-phase voltage feed. A soft-start circuit is implemented at the input of the rectifier. This circuit removes any harmful in-rush currents common in power electronic equipment and ensures a smooth start-up of the converter. This improves the reliability of DC bus components and reduces the power quality impact on the customer’s adjacent electrical equipment. A diode-bridge rectifier is utilized to rectify the incoming AC voltage to a nominal DC voltage of 680Vdc. Snubber circuits are utilized in the rectifier to reduce voltage spikes at the diode terminals, thereby improving reliability. To filter the inherent ripple present in the rectified line voltage, a heavy-duty iron-core inductor is utilized. This also provides immunity against momentary line voltage sags.
The inverter module is connected to the filtered DC bus. The inverter module consists of high quality dry-type film capacitors which provide exceptional lifetime reliability. Conservatively rated IGBT’s are used to perform the switching PWM function. A high efficiency heatsink and blower are integrated in the inverter module for optimal cooling. The inverter module has in-built output current, DC voltage, heatsink and IGBT temperature sensing for feedback to the controller.
The PWM ripple at the output of the inverter module is filtered using conservatively rated dry-type AC film capacitors. This ensures a smooth sinewave output to the customer’s 400Hz loads. A transformer is typically utilized at the output of the frequency converter to scale the output voltage to the particular product requirements and provide a 4-wire output for any single phase loads. This transformer is constructed using iron-core and copper winding ensuring high conversion efficiency.
Apart from the sensors provided in the inverter module, precision voltage and current sensors are employed at the output of the frequency converter. The voltage sensors are utilized to control the output voltage of the frequency converter in a closed-loop, real-time fashion. This ensures precise and stable output voltage even in the face of changing utility and load conditions. The voltage and current sensors are also utilized to calculate the real-time output power of the frequency converter. In all, the following signals are reported on the touch-screen operator interface:
- RMS output line-neutral voltages Van, Vbn, Vcn
- RMS output line-line voltages Vab, Vbc, Vca
- RMS output current Ia, Ib, Ic
- Output frequency
- Output active (kW), reactive (kVAR) and apparent (kVA) power
- RMS inverter modules currents Iu, Iv, Iw
- DC link voltage
- Inverter heatsink temperature
- Inverter IGBT temperature
- Realtime controller temperature
The frequency converters use an advanced digital controller that uses a combination of real-time microprocessor and FPGA to control and monitor the unit. In addition to controlling the start-up, runtime and shutdown sequences of the converter, the controller also implements converter protection to prevent failures or damage to the unit. These protective functions are in addition to the hardware protection within the converter such as circuit breakers, fuses, surge-protectors, relays, etc. The following protective trips are implemented:
- Diode module overtemperature
- Inverter module overtemperature
- Cabinet overtemperature
- Transformer overtemperature
- Choke overtemperature
- Input phase-voltage monitor
- DC link overvoltage
- Output overvoltage
- Output overcurrent
The converters are equipped with an easy to operate touch screen. The touch screen allows the end-user to operate and monitor the frequency converter. The current operating electrical parameters such as output voltage, power, etc. are available. The current operating status and any trips and alarms are also displayed on the touch screen.
Nominal input voltage: 380, 400, 415, 440, 480
Frequency: 45 to 65 Hz
Power Factor: >0.95 at 100% load
Current Harmonic Distortion, (THDi): <2% Soft Start: 0 to 100% in 60 seconds, adjustable
Rated Output Power (kVA): 20, 40, 62.5, and 125 KVA
Nominal Current, Nominal Output Voltage: 200/115 Vac 3Ph + N “Y” Static stability, +1%
Dynamic Stability: +1%
Voltage Distortion with Linear Load: <3%
Voltage Distortion with non-Linear Load: <4%
Overload: > In. x 1.1 for 60 minutes> In. x 2.0 for 1 second> Efficiency up to 99%
Noise Level: <63 dBA at 1m
Operating Ambient Temperature: O °C to 40 °C (Operation in an ambient temperature of 50°, the converter output is reduced by 25%)
Relative Humidity: <95% non-condensing
Ingress Protection Degree: IP20 as standard, options available
Safety: EN 62040-1-1 (Directive 2006/95/ECJ); EMC, EN 62040-2 (Directive 2004/108/EC) Classification as per IEC 62040-3 (Voltage Frequency Independent) VFI-SS-111Installation, indoors for IP20