G'day
Once again I have been thinking how I do my designs and how to improve.
Generally when designing VSD (Variable Speed Drives - electronic type) circuits I will take a feed from the 3 phase bus, run it through a motor circuit breaker (thermal and magnetic type - this way I can avoid a thermal overload relay), then through a contactor and then to the VSD. Post VSD I would run it straight to the motor, often via a field isolator depending on other design factors.
Due to safety requirements, the 3 phase bus is normally supplied via double contactors wired to the safety circuitry.
Recently, I have seen some designs that do away with the motor contactor supplying the VSD, and connect straight to the circuit breaker. This seems a good idea to me, since under most conditions the extra contactor seems to be redundant. If the safty circuit is tripped, the double contactors up-stream of the bus will take care of it.
What are your thoughts?
Would this be a better design method?
How do you guys normally design these circuits?
Thanks in advance
Doug
Once again I have been thinking how I do my designs and how to improve.
Generally when designing VSD (Variable Speed Drives - electronic type) circuits I will take a feed from the 3 phase bus, run it through a motor circuit breaker (thermal and magnetic type - this way I can avoid a thermal overload relay), then through a contactor and then to the VSD. Post VSD I would run it straight to the motor, often via a field isolator depending on other design factors.
Due to safety requirements, the 3 phase bus is normally supplied via double contactors wired to the safety circuitry.
Recently, I have seen some designs that do away with the motor contactor supplying the VSD, and connect straight to the circuit breaker. This seems a good idea to me, since under most conditions the extra contactor seems to be redundant. If the safty circuit is tripped, the double contactors up-stream of the bus will take care of it.
What are your thoughts?
Would this be a better design method?
How do you guys normally design these circuits?
Thanks in advance
Doug