locked rotor torque 3

[Baz2]

I hope someone can help me determine the locked rotor torque for a 110 volt AC, Capacitor-Start, 1/2 HP, single phase motor.
If anyone has a structural problem I may be able to help!
Looking forward to your help,
Baz2

 

[itsmoked]

I suspect that will be nearly impossible to guess at. Three phase perhaps. But single? Not likely. Have you checked with the manufacturer?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

First off on single phase cap-start motors, "Locked Rotor" torque is different than on 3 phase motors because of the capacitor starting. LRT in this case is peak starting torque when the cap is still in the circuit (or technically, if you lock the rotor and the start cap is once again back in the circuit). Are you sure you don't want maximum developed torque when the motor is already running? That is usually more useful for mechanical issues.

Then you need to also more accurately identify the motor. Cap-Start / Induction-Run or Cap-Start / Cap-Run? It makes a big difference.

Peak starting torque, caps in the circuit, with a Cap-Start / Induction-Run motor can be as high as 350% FLT at zero speed. With a Cap-Start / Cap-Run it can be 190-200% FLT at zero speed. Peak running torque, after the start switch is closed, is around 240-250% on both designs.

 

[Baz2]

jraef: Thanks for your info: Yes, I will need the safe running torque when the motor is already running. I'm not sure of the motor identification regarding Cap-Start/Induction Run versus Cap Start/Cap Run: I have never seen this info on a motor identification plate.
I have a condition where I have to accelerate a 350 Lb. load from rest to a velocity of 4 inches per sec. I need the LRT to determine the acceleration of the load.
Baz2

 

[Marke]

Hello Baz2

The only way to get the LRT of the specific motor that you are looking at, is to get it from the manufacturer or the manufacturers agent.
The LRT for induction motors varies over a wide range (greater than 2 : 1) for motors that appear to be basically the same.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[waross]

I had two 1/2 hp capacitor start motors in an application that demanded a high starting torque but had managable running torque. The motors would stall rather than start the loads. Before discarding the motors and installing 3/4 hp motors, we doubled the size of the starting capacitors. They have been starting and running happily for years now.

Bill
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