Arrangement for monitoring a frequency converter

• US 7,688,603 B2
• Filed: 05/02/2006
• Issued: 03/30/2010
• Est. Priority Date: 05/03/2005
• Status: Expired due to Fees

• Current Assignee: Vacon Oy (Danfoss A/S)
• Original Assignee: Vacon Oyj (Danfoss A/S)
• Inventors: Pakkala, Janne, Komulainen, Risto
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US11/415,190
• Publication Number:
  US 20060265160A1
• Time in Patent Office: 1,428 Days
• Field of Search: 363/35, 363/37, 363/50, 363/55, 363/74, 363/78, 363/95, 363/132
• US Class Current: 363/37
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 5/458 using semiconductor devices only

Abstract

An arrangement and method for monitoring a frequency converter, the frequency converter being a voltage-controlled PWM frequency converter provided with a control unit and having an uncontrolled or a main-frequency controlled main bridge connectable to an alternating-current source (U_L1, U_L2, U_L3), a direct-voltage intermediate circuit and a controlled load bridge for producing a variable-frequency multi-phase output voltage (U_U, U_V, U_W), which direct-voltage intermediate circuit of the frequency converter is provided with a small-capacitance direct-voltage capacitor, the main bridge being connected to the load bridge directly without a large-capacitance direct-voltage capacitor functioning as an intermediate energy storage, and the arrangement includes a measuring unit for measuring the direct voltage of the intermediate voltage circuit. In the arrangement, the measuring unit measures at least one quantity of the intermediate-circuit direct voltage, and the control unit determines on the basis of the aforesaid quantity at least one input voltage value and/or a failure situation of the frequency converter or its load circuit.

Claims

1. A method for monitoring a frequency converter,

said frequency converter being a voltage-controlled PWM frequency converter having an uncontrolled main bridge connectable to an alternating-current source (U_L1, U_L2, U_L3), a direct-voltage intermediate circuit and a controlled load bridge for producing a variable-frequency multi-phase output voltage (U_U, U_V, U_W),

said direct-voltage intermediate circuit of the frequency converter is provided with a small-capacitance direct-voltage capacitor, the main bridge being connected to the load bridge directly without a large-capacitance direct-voltage capacitor functioning as an intermediate energy storage, and

in which method the direct voltage of the intermediate voltage circuit is measured,

the method comprising the steps of:

sizing a capacitance value of the small-capacitance direct-voltage capacitor so that the direct voltage of the intermediate voltage circuit varies strongly and follows a highest main voltage of the source,

measuring at least one quantity of the intermediate-circuit direct voltage, and

determining on the basis of the aforesaid quantity at least one input voltage value and/or a failure situation of the frequency converter or its load circuit,

wherein an a.c. source and the main bridge are three-phase, and

the failure situation is a short circuit which is identifiable so that a d.c. level drops to a value less than predetermined value.

2. A method according to claim 1, wherein said quantity is the voltage value of the direct-voltage peaks, on the basis of which is determined the voltage of the alternating-current main supply network.

3. A method according to claim 1, wherein said quantity is the time between peaks of the direct voltage, on the basis of which is determined the frequency of the alternating-current main supply network.

4. A method according to claim 1, wherein said quantity is the voltage value of the peaks of the direct voltage, on the basis of which is determined the asymmetry of the alternating-current main supply network.

5. A method according to claim 1, wherein said quantity is the direct-voltage level and the failure situation is a short-circuit situation, which is detected from the direct voltage level falling rapidly down.

6. A method according to claim 1, wherein said quantity is the voltage value of the peaks of the direct voltage, on the basis of which is determined the asymmetry of the alternating-current main supply network, and

wherein said quantity is the direct-voltage level and the failure situation is a short-circuit situation, which is detected from the direct voltage level falling rapidly down.

7. A method according to claim 1, wherein the main bridge is a rectifying bridge.

8. A method according to claim 1, wherein the main bridge includes rectifying diodes.

9. A method according to claim 1, wherein the step of measuring at least one quantity of the intermediate-circuit direct voltage includes measuring at least two quantities of the intermediate-circuit direct voltage.

10. A method according to claim 1, wherein the step of measuring at least one quantity of the intermediate-circuit direct voltage is performed by a measurement unit that is arranged in parallel to the small-capacitance direct-voltage capacitor.

11. A method according to claim 1, wherein the measurement unit is arranged in parallel to the small-capacitance direct-voltage capacitor.

12. A method according to claim 1, wherein the at least one supply voltage value and/or the failure situation is determined by a measurement unit that is arranged in parallel to the small-capacitance direct-voltage capacitor.

13. An arrangement for monitoring a frequency converter,

said frequency converter being a voltage-controlled PWM frequency converter provided with a control unit and having an uncontrolled main bridge connectable to an alternating-current source (U_L1, U_L2, U_L3), a direct-voltage intermediate circuit and a controlled load bridge for producing a variable-frequency multi-phase output voltage (U_U, U_V, U_W),

said direct-voltage intermediate circuit of the frequency converter is provided with a small-capacitance direct-voltage capacitor, the main bridge being connected to the load bridge directly without a large-capacitance direct-voltage capacitor functioning as an intermediate energy storage, the arrangement comprising:

a measuring unit for measuring the direct voltage of the intermediate voltage circuit,

wherein the measuring unit measures at least one quantity of the intermediate-circuit direct voltage, and

the control unit determines on the basis of the aforesaid quantity at least one input voltage value and/or a failure situation of the frequency converter or its load circuit,

wherein an a.c. source and the main bridge are three-phase, and the failure situation is a short circuit which is identifiable so that a d.c. level drops to a value less than predetermined value,

wherein a capacitance value of the small-capacitance direct-voltage capacitor is set so that the direct voltage of the intermediate voltage circuit varies strongly and follows a highest main voltage of the source.

14. An arrangement according to claim 13, wherein said quantity is the voltage value of the direct-voltage peaks, on the basis of which is determined the voltage of the alternating-current main supply network.

15. An arrangement according to claim 13, wherein said quantity is the time between peaks of the direct voltage, on the basis of which is determined the frequency of the alternating-current main supply network.

16. An arrangement according to claim 13, wherein said quantity is the voltage value of the peaks of the direct voltage, on the basis of which is determined the asymmetry of the alternating-current main supply network.

17. An arrangement according to claim 13, wherein said quantity is the direct-voltage level and the failure situation is a short-circuit situation, which is detected from the direct voltage level falling rapidly down.

18. An arrangement according to claim 13, wherein the measurement unit for measuring at least one quantity of the intermediate-circuit direct voltage measures at least two quantities of the intermediate-circuit direct voltage.

19. Use of direct-voltage measurement of the intermediate voltage circuit of a frequency converter, said frequency converter being a voltage-controlled PWM frequency converter having an uncontrolled main bridge connectable to an alternating-current source (U_L1, U_L2, U_L3), a direct-voltage intermediate circuit and a controlled load bridge for producing a variable-frequency multi-phase output voltage (U_U, U_V, U_W), which direct-voltage intermediate circuit of the frequency converter is provided with a small-capacitance direct-voltage capacitor, the main bridge being connected to the load bridge directly without a large-capacitance direct-voltage capacitor functioning as an intermediate energy storage,

to determine at least one supply voltage value and/or a failure situation of the frequency converter or its load circuit,

wherein an a.c. source and the main bridge are three-phase, and the failure situation is a short circuit which is identifiable so that a d.c. level drops to a value less than predetermined value,

wherein a capacitance value of the small-capacitance direct-voltage capacitor is set so that the direct voltage of the intermediate voltage circuit varies strongly and follows a highest main voltage of the source.