nathanht
Member
Hi;
I have a project I am designing to run multiple 3 phase induction motors from 1 vfd. I have two motor starters , one is connected from the output of the vfd
To the motor, the other is connect from line to the motor. The vfd has flying start which gives it the ability to catch a motor while it is still spinning. I monitor the speed of the vfd from an analog output of the vfd to a PLC. When the VFD reaches 60 hz the PLC disables the vfd and switches the motor to the line contactor.
When the speed drops below 60 hz the PLC switches the motor back to the vfd, re-enables the vfd and sends a start command.. All this works nicely except when the motor goes from the vfd to to line most of the time I get a thump which could damage couplings. Some people have told me I can eliminate this by zero cross detection, can I use a PLC for this does anyone have any suggestions?
I have a project I am designing to run multiple 3 phase induction motors from 1 vfd. I have two motor starters , one is connected from the output of the vfd
To the motor, the other is connect from line to the motor. The vfd has flying start which gives it the ability to catch a motor while it is still spinning. I monitor the speed of the vfd from an analog output of the vfd to a PLC. When the VFD reaches 60 hz the PLC disables the vfd and switches the motor to the line contactor.
When the speed drops below 60 hz the PLC switches the motor back to the vfd, re-enables the vfd and sends a start command.. All this works nicely except when the motor goes from the vfd to to line most of the time I get a thump which could damage couplings. Some people have told me I can eliminate this by zero cross detection, can I use a PLC for this does anyone have any suggestions?