Frequency converter, motor, motor drive system and maintenance method for motor drive system
View Patent ↗A frequency converter for outputting a power to drive a motor, having: an inverter unit for inverting a d.c. power to an a.c. power; a control unit for controlling the inverter unit; and a housing for supporting at least the inverter unit and control unit, wherein a rise time change unit is provided in the housing, the rise time change unit changes a rise time of a waveform of a voltage output from the inverter unit.
1. A frequency converter for outputting an a.c. power to drive a motor, comprising:
an inverter unit for inverting a d.c. power to an a.c. power;
a control unit for controlling said inverter unit; and
a housing for supporting at least said inverter unit and said control unit,
wherein a rise time change unit is provided in said housing, said rise time change unit changes a rise time of a waveform of a voltage of the a.c. power output from said inverter unit, and
said rise time change unit comprises a core-less reactor coil whose inductance value L is defined by the following equation:
L=k*p*T *( a*a )*( N*N )/ b
wherein L (henry) is equal to or larger than 0.0003 mH and equal to or smaller than 0.2 mH, k is Nagaoka coefficient, μ equals 4*π*10 −7 , π is circular constant, a is coil diameter (meter), b is coil length (meter), and N is the number of coil turns.
2. The frequency converter according to claim 1 , wherein in a case that frequency converter outputs M-phase a.c. power, said rise time change unit is provided for each phase so that M pieces of rise time change units are provided, where M is an integer number not less than two.
3. The frequency converter according to claim 1 , wherein in a case that frequency converter outputs 3-phase a.c. power, said rise time change unit is provided for each phase so that 3 pieces of rise time change units are provided.