Frequency converter with an intermediate buck-boost converter for controlling an electric motor

• US 6,373,728 B1
• Filed: 09/27/2000
• Issued: 04/16/2002
• Est. Priority Date: 09/27/1999
• Status: Expired due to Fees

• Current Assignee: Grunfos A/S
• Original Assignee: Grundfos A/S (Poul Due Jensens Fond)
• Inventors: Aarestrup, Jan Carøe
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/671,218
• Time in Patent Office: 566 Days
• Field of Search: 363/34, 363/37, 363/89, 363/132
• US Class Current: 363/37
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: H02P 6/085 in a bridge configuration

Abstract

The frequency converter is provided for an electric motor and comprises a rectifier, an intermediate circuit and an inverse rectifier which are connected with respect to circuiting technology via a control and regulation circuit. In the inverse rectifier to each motor phase there are allocated at least two electronic switches, one for the side conducting the higher potential and one for the side conducting the low potential. The intermediate circuit is formed as an active intermediate circuit and contains a Buck-Booster converter. It is controlled such that the voltage at the output of the intermediate circuit with respect to magnitude is always smaller than that at the input. By way of this inexpensive components may be used in the inverse rectifier and in particular also in the control and regulation circuit.

Claims

1. A frequency converter for an electric motor having at least one phase, comprising:

a rectifier having a rectifier output;

an intermediate circuit with a buck-boost converter having an intermediate circuit input connected to said rectifier output and an intermediate circuit output;

an inverse rectifier having an inverse rectifier input connected to said intermediate circuit output, a high-side conducting a higher potential and a low-side conducting a lower potential, and a pair of electronic switches for each phase of the at least one phase of the electric motor, wherein one switch of said pair of electronic switches is connected to said low side and the other switch of said pair of electric switches is connected to said high side; and

a control and regulation circuit operatively arranged for controlling said intermediate circuit such that a magnitude of voltage at said intermediate circuit output is always smaller than a magnitude of voltage at said intermediate circuit input.

2. The frequency converter of claim 1, wherein said one switch of said pair of electronic switches connected to said low side comprises n-type doping semiconductors and said other switch of said pair of electronic switches connected to said high side comprises p-type doping semiconductors.

3. The frequency converter of claim 1, wherein said intermediate circuit comprises a high side connected to a higher potential conductor and a low side connected to a lower potential conductor,

said buck-boost converter comprises a buck-boost rectifier diode and an electronic switch, and

said buck-boost rectifier diode is connected to one of said high and low sides of said intermediate circuit and said electronic switch is connected to the other one of said high and low sides of said intermediate circuit.

4. The frequency converter of claim 1, wherein a voltage at said intermediate circuit output is within a range including 30 to 70 Volts and a power of the frequency converter is within a range including 50 to 300 Watts.

5. The frequency converter of claim 4, wherein said voltage at said intermediate circuit output comprises 50 Volts.

6. The frequency converter of claim 1, wherein said frequency converter is operatively arranged for pulse-amplitude-modulated control of the electric motor.