Logic To Power Interface; Power Section; Sequence Of Operation; Rectifier Section - Trane TR150 Service Manual

Internal Frequency Converte...

3.2.2 Logic to Power Interface

The logic to power interface isolates the high-voltage
components of the power section from the low voltage
signals of the logic section. The interface consists of two
sections.
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Power Card
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Gate Driver
The control card handles much of the fault processing for
output short circuit and ground fault conditions. The
power card provides conditioning of these signals. Scaling
of current feedback and voltage feedback is accomplished
on the interface sections before processing by the control
card.
The power card contains a Switch Mode Power Supply
(SMPS). The SMPS provides the unit with 24 V DC, 16 V DC,
7 V DC, 6 V DC, and 3.3 V DC operating voltage. SMPS
powers the logic and interface circuitry. SMPS is supplied
by the DC bus voltage. A secondary SMPS provides power
to the logic circuitry with main input disconnected. It can
keep units with communication options live on a network
when the frequency converter is not powered from the
mains.
Circuitry for controlling speed of the cooling fans is also
provided on the power card.

3.2.3 Power Section

The DC coil is a single unit 2 two coils wound on a
common core. One coil resides in the positive side of the
DC bus and the other in the negative. The coil aids in the
reduction of mains harmonics.
The DC bus capacitors are arranged into a capacitor bank
along with bleeder and balancing circuitry.
The inverter section is made up of six IGBTs, commonly
referred to as switches. One switch is necessary for each
half phase of the 3-phase power, for a total of 6. The 6
IGBTs are contained in 3 dual modules.
A Hall effect type current sensor is located on each phase
of the output to measure motor current.
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Illustration 3.2 Typical Power Section

3.3 Sequence of Operation

3.3.1 Rectifier Section

The rectifier provides a path for current flowing from the
line to the DC-link circuitry. As a result, the DC-link
capacitors charge.
The rectifier section consists of 6 diodes.
Inrush current, which appears when connected to grid, is
limited with a PTC. A relay short-circuits the PTC when the
DC-link capacitors are fully charged.
As long as power is applied to the frequency converter,
voltage is present in the DC link and the inverter circuit.
Voltage is also fed to the switch mode power supply
(SMPS) on the power card and is used for generating all
other low voltage supplies.

3.3.2 Intermediate Section

From the rectifier section, voltage passes to the
intermediate section. The DC link is an LC filter circuit
consisting of the DC-link inductor and the DC-link
capacitor bank that smooths the rectified voltage.
The intermediate section consists of the following
components:
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The DC-link inductor located in the positive side
of the DC link provides series impedance to
changing current. This impedance aids the
filtering process while reducing harmonic
distortion to the input AC current waveform
normally inherent in rectifier circuits.
The DC-link capacitors are arranged into a
capacitor bank along with bleeder and balancing
circuitry.
High frequency (HF) filter film capacitors. These
capacitors reduce the common mode noise
caused by switching into stray capacitors to
ground in cable and motor.
BAS-SVM04B-EN