Kemppi KEMPACT 181A, Service Manual, Page: 19 / 40

SERVICE MANUAL
KEMPACT RA_V_1.2 18 (40)
Kemppi Oy
3.4. Main circuit diagram 253MV-, 323MV-models
3.4.1. General
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323 MV and 253 MV machines have many common technical details with the 323 and 253 machines. They have e.g.
the same Z002, A001 and P001 cards. Also main transformers are same. Main difference is of course that they are
multi voltage machines. This means that these machines can be connected to any mains voltage between 230V -15%-
400V +15%. The selection of input voltage is automatic. In fact, the multi voltage machines use basically the same
technology as the one phase machines. This means that there is first a boost type converter which raises rectified in-
put voltage to approximately 630V DC-link voltage. This DC-link voltage is then used as input voltage for the H-bridge.
So PFC boost is used as an input stage for the H-bridge. Regardless of input voltage (230V -15% - 400V +15%) boost
stage raises DC-link voltage to same value so the input voltage to the H-bridge stays the same.
3.4.2. Main circuit card Z001
3.4.2.1. EMC filter
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Capacitors C5 – C10 and inductor T6 forms an EMC filter
3.4.2.2. Inrush current limiting
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PTC resistor R70 limits inrush current when the power source is switched on
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PTC is bypassed with relays K1 and K2 after DC link capacitors have been charged
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Relays K1 and K2 are controlled with the microcontroller
3.4.2.3. IGBT driver
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IGBT driver consists of gate transformers T2 and T3 and surrounding components
3.4.2.4. Current transformer T1
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Current transformer T1 is monitoring primary current and stops power stage operation if current is raising too high
3.4.2.5. Main circuit
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The main circuit consists of boost type PFC circuit followed by H-bridge type converter.
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Both parts of the main circuit are implemented using the same 1200V, 100A six pack IGBT module
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One leg of the IGBT module is used for the Boost PFC circuit. Lower IGBT is used as the Boost power switch and the
anti-parallel diode of the upper IGBT as the boost diode. H – bridge is implemented using the other two legs of the
IGBT module
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The switching frequency of the boost circuit is ca. 13 kHz. The boost circuit raises DC link voltage to ca. 630V. Boost
input current is measured using shunt resistors R58, R59, R65, R66.
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The operation of the H-bridge is the same as with the 323 and 253 machines.
3.4.2.6. PFC Boost control circuitry
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PFC control circuitry is located on the primary side. Auxliary transformer T003 supplies operating voltage for the PFC
control circuitry. The output voltage of the T003 is first rectified and then linear regulator is used to regulate auxiliary
voltage to 15V. PFC control IC N1 regulates DC-link voltage to approximately 630V.