three phase motors and starters

[aaran]

random one for you all

if i say had a 3kw DOL starter + thermal overload and ran 2x 0.18kw fans on them would it cause any issues?

that aside i need a new 0.18kw fan for my booth extraction. one of the ones in there gets overly hot after 20 mins or so and then it causes a complete trip on the main breaker on the 3 phase supply into the workshop. (its not the bearings, assuming the armature or windings are shot, fan mech spins super free as does the motor, its not got duff bearings and the fans not binding anywhere)

specs on the current one are (its an old AESA , now abb correct?)

mot.3 - 50hz class b
0,18kw 1370r/min
380-420 v - 08a

just stuck on the number of poles on the unit? assuming this refers to the number to poles inside the motor and NOT the number of terminals for the 3 phase inbound supply correct?

see a 2 pole motor will spin at 2400 rpm, but a 4 pole motor will spin at 1400. taking a punt that the more poles the slower it turns but the more torque is generated correct?

 

[rtbcomp]

see a 2 pole motor will spin at 2400 rpm, but a 4 pole motor will spin at 1400. taking a punt that the more poles the slower it turns but the more torque is generated correct?

For given power, yes. Power = Torque x speed

 

[Luke]

It won't cause any immediate issues, but the motors won't be protected. Is it not advisable to do this.

An induction motor will run synchronous to line frequency, less torque-generating slip. Poles refers to the number of magnetic poles in each of the motor windings. The synchronous speeds for 50Hz are as follows;
2 pole - 3000 RPM
4 pole - 1500 RPM
6 pole - 1000 RPM

An induction motor will run at around the following speeds when loaded.
2 pole - 2800 RPM
4 pole - 1400 RPM
6 pole - 900 RPM

The exact running speed will depend on the motor itself. If the motor is controlled by an inverter with either vector control or an encoder, synchronous speed can be achieved and maintained.

For a given frame size, the power will be relatively constant. As Roger says, Power = Torque x Speed, so changing the number of poles will inversely affect the torque rating of the motor.

Motors will normally have 6 terminals for the windings, arranged in either star or delta, via link bars, plus a terminal for a PE (protective earth) connection.

Luke

 

[aaran]

cheers luke. will just replace with the exact same one as the one i took out

think this is the last motor i have thats failed (normally been bearings but given that most of them are from the 70's and the heater fan is from 1965 according to the heater info plate its lasted well!)

need my full extraction back for painting and need to get the tank filled with gasoil for the heater and the motor back in for some heat for the booth and workshop. already had a batch of parts bloom over night due to the temps thankfully it all polished right out!