US 11,870,384 B2
Speed calculation device and power conversion device
Hiroshi Watanabe, Tokyo (JP); Masataka Sasaki, Tokyo (JP); Masahiro Hiraga, Tokyo (JP); Yusuke Arao, Tokyo (JP); Atsuhiko Nakamura, Tokyo (JP); Hiroyuki Tomita, Tokyo (JP); Kazushige Hotta, Tokyo (JP); and Yusaku Onuma, Tokyo (JP)
Assigned to Hitachi Industrial Equipment Systems Co., Ltd., Tokyo (JP)
Appl. No. 16/644,207
Filed by Hitachi Industrial Equipment Systems Co., Ltd., Tokyo (JP)
PCT Filed Jun. 13, 2018, PCT No. PCT/JP2018/022567
§ 371(c)(1), (2) Date Mar. 4, 2020,
PCT Pub. No. WO2019/073633, PCT Pub. Date Apr. 18, 2019.
Claims priority of application No. 2017-196591 (JP), filed on Oct. 10, 2017.
Prior Publication US 2021/0075347 A1, Mar. 11, 2021
Int. Cl. H02H 3/44 (2006.01); H02P 1/18 (2006.01); H02P 6/17 (2016.01)
CPC H02P 6/17 (2016.02) 14 Claims
OG exemplary drawing
 
1. A speed calculation device that calculates a speed of an object to be driven from output pulses obtained from an encoder connected to the object to be driven,
wherein a duty ratio of a time of a half cycle from a rising edge to a falling edge of the output pulses to a time of a full cycle between rising edges of the output pulses is measured based on a motor speed instruction,
wherein the speed calculation device outputs a duty measurement-in-progress signal while the duty ratio is being measured, and the motor speed instruction is fixed to a most recently determined value while the duty measurement-in-progress signal is being outputted,
wherein the speed is calculated using the half cycles of the output pulses if the duty ratio is within a prescribed range, and
wherein the speed is calculated using the full cycles of the output pulses if the duty ratio is outside of the prescribed range.