Patent ID: 11955911
Assignee: MEIDENSHA CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  G | IPC G  H

Claim 6:
7. A demagnetization diagnosis method for a motor control device, wherein the motor control device includes:
a power converter including: a first switch element and a second switch element connected to each other in series between a first end and a second end of a capacitor; a third switch element and a fourth switch element connected to each other in series between the first end and the second end of the capacitor; and a fifth switch element and a sixth switch element connected to each other in series between the first end and the second end of the capacitor; and
a motor including: a first winding connected to a connection point common between the first switch element and the second switch element; a second winding connected to a connection point common between the third switch element and the fourth switch element; and a third winding connected to a connection point common between the fifth switch element and the sixth switch element;
the demagnetization diagnosis method comprising:
with use of a pulse voltage generator, calculating a corrected pulse voltage application time period by a Mathematical Expression 6 below, and selecting a voltage vector nearest to a rotor phase of a rotor of the motor out of voltage vectors V1 to V12 shown in a Table 1 below, and outputting the selected voltage vector as a voltage vector command, for the corrected pulse voltage application time period;
with use of a current measurement circuit, measuring output currents of three phases of the power converter outputted when the first to sixth switch elements of the power converter are turned ON or OFF in accordance with the Table 1 in response to the voltage vector command; with use of a three-phase/two-phase converter, converting the output currents of the three phases into output currents of two phases, and outputting a d-axis current and a q-axis current; and with use of a demagnetization determiner, determining demagnetization as occurring in a permanent magnet of the rotor of the motor, in response to satisfaction of a condition that an alternating-current effective value calculated from the d-axis current and the q-axis current after passage of the corrected pulse voltage application time period is equal to or less than a demagnetization determination threshold, [
     
      Mathematical
      ⁢
         
      Expression
      ⁢
         
      6
     
     ]
    
   
   
    
   
  
  
   
    
     
      Ton
      ′
     
     =
     
      Ton
      
       
        
         
          cos
          2
         
         (
         
          Δ
          ⁢
          θ
         
         )
        
        +
        
         
          (
          
           
            
             L
             ⁢
             d
            
            
             L
             ⁢
             q
            
           
           *
           
            sin
            ⁡
            (
            Δθ
            )
           
          
          )
         
         2
        
       
      
     
    
   
   
    
     (
     6
     )
    
   
  
 

Ton: Pulse voltage application time period before correction (fixed value)
Ton′: Pulse voltage application time period after correction
Δθ: Absolute value of difference between current rotor phase γ and phase of voltage vector command
Ld: d-axis inductance
Lq q-axis inductance, TABLE 1

FIRST
SECOND
THIRD
FOURTH
FIFTH
SIXTH

SWITCH
SWITCH
SWITCH
SWITCH
SWITCH
SWITCH

ELEMENT
ELEMENT
ELEMENT
ELEMENT
ELEMENT
ELEMENT

V1
ON
OFF
OFF
ON
OFF
ON

V2
ON
OFF
OFF
OFF
OFF
ON

V3
ON
OFF
ON
OFF
OFF
ON

V4
OFF
OFF
ON
OFF
OFF
ON

V5
OFF
ON
ON
OFF
OFF
ON

V6
OFF
ON
ON
OFF
OFF
OFF

V7
OFF
ON
ON
OFF
ON
OFF

V8
OFF
ON
OFF
OFF
ON
OFF

V9
OFF
ON
OFF
ON
ON
OFF

V10
OFF
OFF
OFF
ON
ON
OFF

V11
ON
OFF
OFF
ON
ON
OFF

V12
ON
OFF
OFF
ON
OFF
OFF.