傳統的繼電器控制系統使用了大量的中間繼電器、時間繼電器，由于觸點接觸不良，容易出現故障。PLC用軟件代替大量的中間繼電器和時間繼電器，僅剩下與輸入和輸出有關的少量硬件元件，接線可減少到繼電器控制系統的1/10-1/100，因觸點接觸不良造成的故障大為減少。主電路是給異步電動機提供調壓調頻電源的電力變換部分，變頻器的主電路大體上可分為兩類：電壓型是將電壓源的直流變換為交流的變頻器，直流回路的濾波是電容。鄭工1995 9281761

YOKOGAWA 251-340-LSLS     251340LSLS
YOKOGAWA 251-340-LSLS   251340LSLS
YOKOGAWA 251340LSMT     251340LSMT
YOKOGAWA 251340LSND PANEL METER RANGE: 0-15 AC AMPERES,      *
YOKOGAWA 251-340-LSNG     251340LSNG
YOKOGAWA 251-340-LSNW 0-60 AMP GAUGE       IN BOX
YOKOGAWA 251-340-LSNW   251340LSNW
YOKOGAWA 251-340-LSPB     251340LSPB
YOKOGAWA 251-340-LSPD     251340LSPD
Yokogawa 251340LSPK 0-100AC Panel Mount Amp Meter
YOKOGAWA 251-340-LSPK     251340LSPK
YOKOGAWA 251-340-LSPK     251340LSPK
YOKOGAWA 251-340-LSPZ7AAK   251340LSPZ7AAK
Yokogawa 251340LSRL A-C Amperes Meter Panel Mount
Yokogawa 251340LSSC 0-400 A-C Amperes Panel Mount Meter
Yokogawa 251340LSSJ Panel Meter 0-600 AC Amps
Yokogawa 251340LSSJ Panel Meter 0-600 AC Amps
Yokogawa 251340LSV Meter Gauge 0-5 Amp *      in Box**
Yokogawa 251340NT-NT7 0-50 AC Ampere Panel Meter, NIB
YOKOGAWA 251340PDPD7 *      IN BOX*
YOKOGAWA 251-340-XXXX     251340XXXX
YOKOGAWA 251344NEN17 AC VOLTS 0-30 *      IN A BOX*
YOKOGAWA 251344NLN17 0-30 A-C VOLTS PANEL METER *      IN A BOX*
YOKOGAWA 251344PDPD7JHK/UL 0-85 VAC *      IN A BOX*
YOKOGAWA 251-344-PZPZ   251344PZPZ
YOKOGAWA 251344RXRX       YE/251-3 AC VOLTS PANEL METER 251344RXRX
YOKOGAWA 251-344-SJSJ METER *      IN A BOX*
YOKOGAWA 251400FAFA7JJK    251400FAFA7JJK
YOKOGAWA 251400FAFA8JJK    251400FAFA8JJK
Yokogawa 251400HEXX Panel Meter
YOKOGAWA 251-400-LSLS-4UL     251400LSLS4UL