Blower Motor Tripping on Powder Booth

[drcampbell]

... Fan moving at 120% speed requires 173% ( (60Hz/50Hz)³ ) the amount of power from the motor. If we assume the fan needed 2.2kW at 50Hz, it will need 3.8kW at 60Hz, but the motor is only rated for 2.2kW. ... the root cause is the physics. ...

All of the above, plus:
- Hire a mechanical engineer to visit your site and conduct a formal analysis of whether it's reasonable to run this system at 120% of design speed.
- If the answer is yes, buy & install a 3.8 kW (5 Hp) 60-Hz motor. A 3-phase motor if you have 3-phase power available. Replace the motor starter with a larger one if need be.
- If the answer is no, buy & install a 5:6 ratio gearbox.
- If the answer is something else, implement whatever solution your maniacal engineer suggests.
- Bill your time, the engineer's time, and all the other costs of all this rigamarole to whichever sharp-pencil financial genius thought buying a 50-Hz Chinese machine would save money.

 

[retirede]

Another thread where we seem to have lost the OP.

 

[Jraef]

It’s a 3 phase OL relay, but it looks like the single phase motor conductors only use 2 of the 3 poles. These OLs are designed to detect phase loss, so when using on single phase, one of the motor conductors needs to be routed through 2 of the poles so that all 3 poles of the OL see motor current.

Correct.
What this type of IEC OL relay does is that internally there is a "differential bar" with a spring that is acting against the mechanical force exerted by all three current sensing elements. If one element is not exerting any force because there is no current flowing through it to make it bend with the other two, then the spring and bar acts to LOWER the trip threshold of of the relay, meaning the OL will trip with less current than it would with all three phases. If the motor is lightly loaded, this may not cause a trip, because even with the lost phase, the other two have not moved enough. But if the motor is fully loaded, or even slightly over loaded, it will trip at lower levels of current. Given that the motor is definitely going to be over loaded by running over speed, the OL relay will respond accordingly.

 

[ptonsparky]

Another thread where we seem to have lost the OP.

Sometimes I'm wonder if we should be sending get well or sympathy cards. Maybe those We Miss You cards.