variable frequency drive and and standard epact motor
variable frequency drive and and standard epact motor
(OP)
In many building cases we supplied HVAC pumps with standard motor though it will be controlled with frequency inverter ,Normally I use standard epact motor to meet variable frequency needs,but I want to know what variable range is frequency for standard normal motor ?
and under what situation we must use variable frequency drive ?
and under what situation we must use variable frequency drive ?





RE: variable frequency drive and and standard epact motor
This is a practical suggestion. Obviously the frequency inverter will allow the motor to go slower but you may run into motor cooling issues and also the fact that the pump will not be too effective below these suggested frequencies.
I'm not sure that an EPACT motor will have too much difference relating to the speed range, my understanding is that EPACT motors are typically classed as energy efficient (although energy efficient at fixed speed rather than variable speed!).
Your final point "under what situation we must use variable frequency drive ?". I'm not too sure what you mean here. The VFD is intended to control the speed of the motor (and therefore pump) and thus controls the flow/pressure of whatever you are pumping. I think you need to expand on your application to get a more detailed reply to this point.
RE: variable frequency drive and and standard epact motor
Also for your info most compressors are cooled by the refrigerant flowing thru them so speed isn't going to be cooling related since somewhere else a radiator with fans is actually providing the cooling.
RE: variable frequency drive and and standard epact motor
We can guess on the actual application but the easiest way would be for sunloco to advise what it actually is. If it is a centrifugal pump then I would say follow the info I suggested but if it is a compressor then it depends on the type of compressor: screw, scroll, etc and here other factors come into play such as starting torque, lubrication etc
over to you sunloco...
RE: variable frequency drive and and standard epact motor
EPAC motors (Energy Policy Conservation Act) as it was mentioned above are mainly designed to perform with high efficiency that does not necessarily means they are good for VFD application.
Depending on the VFD design high frequency spikes could reduce the insulation or bearing life of a motor to a few hours in operation. It does not mater the motor speed, operating frequency or power output.
Some standard motors have successfully operated with VFDs but others have had almost immediate failure. If you want to ensure successful operation spend the extra money on a VFD duty motor. Other way, you flip a coin and have good luck.
RE: variable frequency drive and and standard epact motor
On the other hand, if "standard motor" is Insulation Class B, the motor is almost surely not suitable for variable speed applications, the only possible exception being 230V service with very short motor leads.
Today, in my view, your best motor value on fan/pump loads is a high efficiency Insulation Class F motor with MG1 Part 31 Endorsement.
RE: variable frequency drive and and standard epact motor
We use the centrifugal pump for HVAC use, the pump will be controlled by frequency inverter.
the motor is from USEM ,380v/3/50HZ,insulation class F,TEFC .
As for what engineer of US motor told me ,the motor can be used in a minimum frequency of 15~20Hz. no necessary to use specical VFD motor.
RE: variable frequency drive and and standard epact motor
As I said in the earlier post, you would be doing a little better with respect to reliability if the motor had a MG1 Part 31 Endorsement in addition to the Class F insulation but it isn't critical as long as you keep the motor lead length reasonably short.
RE: variable frequency drive and and standard epact motor
RE: variable frequency drive and and standard epact motor
ANSI/NEMA MG 1-2003
http://www.nema.org/stds/mg1.cfm (purchase)
http://www.nema.org/stds/mg1condensed.cfm (free download)
Application Guide for AC Adjustable Speed Drive Systems
http://www.nema.org/stds/acadjustable.cfm (free download)