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Do I need encoder feedback?
The enclosure should be a NEMA 12 free-standing flange disconnect enclosure with a circuit breaker. There should be ample room for an AC line reactor and blower motor starter. It is also a good idea to have the keypad operator mounted on the door. If the heatsink is not extended out the back of the enclosure, it will require air-conditioning.
No. The speed regulation of a DC drive is 0.5% with a DC tach, while the speed regulation of an AC drive in Open Loop Vector is 0.2%. Although, an encoder is required on applications associated with web and tension control such as primary and secondary nips or application requiring high precision such as medical tubing. Using an encoder on an extruder will fight the pressure and slowly destroy your gearbox as it is not designed for this servo level response time. If someone recommends a servo performance on a large HP extruder motor, you are listening to the wrong person!
What specifications are important when installing an AC drive in a new enclosure?
Is there a limit of how far away I can mount the AC drive from the motor?
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DC to AC
CONVERSIONS
Doubtful. Just because it fits, does not make it a good idea. AC drives have different heat ratings than DC and the drive may overheat in the same enclosure. This is especially true in applications that are greater than 100 horsepower. The watt loss of the drive can be obtained from the manufacturer to determine if there is appropriate cooling.
No. DC drives are all “Heavy Duty Rated” for applications such as extruders. AC Drives are both “Normal Duty” and “Heavy Duty” rated. Normal Duty is for pumps and fans and has a 110% overload capacity for one minute, while Heavy Duty is for applications such as extruders which has an overload capacity of 150% for one minute. The XD motor is rated at 160% OL for 1 minute, which is even better.
Yes. Distances greater than 150 feet require special provisions to ensure motor reliability which will increase the cost of installation. It is best to mount the drive close to the motor instead of in a control room that is too far away.
Do I need to oversize my AC drive or motor?
Maybe, this is more dependent on your mechanics such as your gearbox and screw than the drive and motor. If the gearbox and screw can take the additional torque and speed, then it is possible to increase the horsepower proportional to the speed resulting in more throughput.
No. You do not need to oversize the drive and motor when converting to AC, as long as you are using the right drive and motor and are not over-exciting the field of the DC motor to increase torque. AC Vector Motors have a wider (CTSR) constant torque speed range (1000:1) as compared to DC motors (10:1). This indicates that it can maintain torque at lower speeds without overheating. Also, AC Vector motors usually have a constant blower fan with filter similar to DC mounted opposite the shaft-end of the motor.
Are AC drives rated the same as DC drives?
Can I put the AC drive in the same enclosure as my DC drive?
Can I increase throughput with a bigger drive?
ICT is a leading organization in the plastics industry that focuses on DC to AC conversions for extruders. With almost 1,000 extruder conversions across the US, we can give you guidence on the selection on the drive of choice, and this drive is the one we designed to specifically address extrusion applications. Selection is simple, match the AC motor amps to the HD rating for the drive. The motor should be vector rated and match the HP and RPM of your existing DC. If you do not have a motor, we can help you there as well! Just ask about the extruder duty motors we carry.
To make things easier, we added this list of commonly asked questions from customers like you asked when converting.