POWER TRANSDUCER

• US 20090224704A1
• Filed: 02/12/2009
• Published: 09/10/2009
• Est. Priority Date: 03/10/2008
• Status: Active Grant

• Current Assignee: Hitachi Industrial Equipment Systems Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Industrial Equipment Systems Company Limited (Hitachi, Ltd.)
• Inventors: Watanabe, Hiroshi, Uchino, Yoshihiro, Ibori, Satoshi, Hiraga, Masahiro
• Granted Patent: US 8,120,294 B2
• Time in Patent Office: Days
• US Class Current: 318/376
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 5/458 using semiconductor devices only
• CPC Class Codes: H02P 3/14 by regenerative braking
• CPC Class Codes: H02P 3/22 by short-circuit or resistive braking

Abstract

The performance of a power transducer is improved while efficiently using a power semiconductor also by managing the permissible duty factor of the power semiconductor in the regenerative braking circuit provided in the power transducer. The user is allowed to set, through an operation panel provided on the power transducer, the resistance value of the regenerative braking resistor for thermally consuming the rotational energy generated during motor deceleration. The power transducer performs the steps of: calculating the current which flows in the regenerative braking circuit from the resistance value setting; obtaining the generation loss of the power semiconductor in the regenerative braking circuit with the calculated current value; and determining the permissible duty factor of the power semiconductor from the obtained generation loss.

Claims

1. A power transducer which outputs AC power having a variable voltage and a variable frequency, the power transducer comprising:

a converter for rectifying the AC voltage of an AC power supply to convert it to a DC voltage;

a DC intermediate circuit having a smoothing capacitor for smoothing the DC voltage of the converter;

a detecting circuit for detecting the voltage of the DC intermediate circuit;

a regenerative braking circuit provided in the DC intermediate circuit;

a drive circuit for driving the regenerative braking circuit when the detecting circuit detects a specified voltage;

a timer for accumulating the operating time of the regenerative braking circuit to obtain the cumulative operating time; and

an inverter for converting the DC voltage of the converter to an AC voltage,

wherein it is possible to individually set a permissible duty factor % ED and a resistance value R of a regenerative braking resistor connected to the regenerative braking circuit provided in the DC intermediate circuit.

2. The power transducer according to claim 1,

wherein the power transducer performs the steps of:

calculating the current which flows in a power semiconductor, a switching element, in the regenerative braking circuit from the resistance value setting of the regenerative braking resistor;

obtaining the generation loss of the power semiconductor from the calculated current value, and;

calculating the permissible duty factor of the power semiconductor.

3. The power transducer according to claim 1, further comprising:

a nonvolatile memory for prestoring correlation data between the generation loss of the power semiconductor in the regenerative braking circuit and the permissible duty factor of the power semiconductor from the resistance value setting of the regenerative braking resistor,

wherein the power transducer reads from the nonvolatile memory the permissible duty factor data of the power semiconductor corresponding to the resistance value setting of the regenerative braking resistor.

4. The power transducer according to claim 2,

wherein the power transducer performs the steps of:

comparing the permissible duty factor of the regenerative braking resistor with the permissible duty factor of the power semiconductor obtained from the resistance value setting of the regenerative braking resistor, and;

automatically disconnecting only the power semiconductor in the regenerative braking circuit without breaking the output of the power transducer when the cumulative operating time obtained by the timer reaches the permissible duty factor of the regenerative braking resistor or the permissible duty factor of the power semiconductor, whichever smaller.

5. The power transducer according to claim 2, further comprising:

a display unit for displaying the permissible duty factor of the power semiconductor calculated or read from the nonvolatile memory.

6. The power transducer according to claim 1,

wherein, when the resistance value setting of the regenerative braking resistor is equal to or less than a predetermined minimum permissible resistance value, the permissible duty factor 0% ED of the power semiconductor is displayed on the display unit.

7. The power transducer according to claim 1,

wherein, when the resistance value setting of the regenerative braking resistor is equal to or less than the predetermined minimum permissible resistance value, symbols or characters for indicating a resistance value setting failure are displayed on the display unit.

8. The power transducer given in claim 5, further comprising:

an operation panel provided in the operation panel for allowing the operator to individually set the permissible duty factor and resistance value of the regenerative braking resistor.