VFD can reduce the frequency. but,
is it any effects of low frequency on induction motor??
is there a minimum limit of frequency to keep motor performance??
is there any equations or formulas to get the minimum limit of frequency??
or if the frequency is too low, what will be happen on induction motor?? is it be off??
if the specification of motor:
744 kW, 6300V, 10 Poles, 600 rpm, 50 Hz
what is the minimum limit of frequency??
please response this topic on this forum or send me an email on akukiajid@yahoo.com
Thanks
Effects Of Low Frequencies On 3phase Induction Motor Performance
Started by ajid, Dec 13 2008 09:43 AM
2 replies to this topic
#2
mariomaggi
-
- Full Member
-
- 234 posts
Senior Member
- Gender:Male
- Location:Milan, Italy
- Interests:electric vehicles http://www.evlist.it , 3-phase AC sources to test PV inverters, high-power AC/DC power supplies up to 1500 VDC to test photovoltaic inverters, bidirectional AC/DC power supplies to test and simulate big batteries, infrared windows for thermography, renewable energies, special electric motors, special inverters, energy savings, power quality
Posted 13 December 2008 - 09:44 PM
ajid,
[quote name='ajid' date='Dec 13 2008, 10:43 AM' post='9621']
> is it any effects of low frequency on induction motor??
no.
>is there a minimum limit of frequency to keep motor performance??
Performances are mainly due to inverter type and feedback control.
> is there any equations or formulas to get the minimum limit of frequency??
I don't think so. Minimum frequency should be also very low, near zero.
> or if the frequency is too low, what will be happen on induction motor?? is it be off??
Performances near zero speed are depending mainly from inverter vector or V/f control
> if the specification of motor:
> 744 kW, 6300V, 10 Poles, 600 rpm, 50 Hz
> what is the minimum limit of frequency??
Minimum speed is related mainly to the type of load (quadratic torque, constant torque, constant power)
Best regards
Mario
[quote name='ajid' date='Dec 13 2008, 10:43 AM' post='9621']
> is it any effects of low frequency on induction motor??
no.
>is there a minimum limit of frequency to keep motor performance??
Performances are mainly due to inverter type and feedback control.
> is there any equations or formulas to get the minimum limit of frequency??
I don't think so. Minimum frequency should be also very low, near zero.
> or if the frequency is too low, what will be happen on induction motor?? is it be off??
Performances near zero speed are depending mainly from inverter vector or V/f control
> if the specification of motor:
> 744 kW, 6300V, 10 Poles, 600 rpm, 50 Hz
> what is the minimum limit of frequency??
Minimum speed is related mainly to the type of load (quadratic torque, constant torque, constant power)
Best regards
Mario
Mario Maggi - Italy - http://www.evlist.it - https://www.axu.it
#3
marke
-
- Moderator
-
- 2,639 posts
Posting Freak
- Gender:Male
- Location:Christchurch, New Zealand
Posted 14 December 2008 - 05:53 PM
As you reduce the frequency applied to an induction motor, it slows down.
This reduces the cooling and therefore you must be careful not to overheat the motor, plus as the frequency reduces, the available power reduces. The torque remains constant, but speed times torque equals power so the power reduces.
At speeds below 10 Hz, the torque in practice will also drop, so if you need high torque, use a gear box to increase the speed of the motor relative to the shaft speed.
Best regards,
Mark.
This reduces the cooling and therefore you must be careful not to overheat the motor, plus as the frequency reduces, the available power reduces. The torque remains constant, but speed times torque equals power so the power reduces.
At speeds below 10 Hz, the torque in practice will also drop, so if you need high torque, use a gear box to increase the speed of the motor relative to the shaft speed.
Best regards,
Mark.
Mark Empson | administrator
Skype Contact = markempson | phone +64 274 363 067
LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users
