Motor ID help for electrical novice.

[dephill]

Hi all,
I have a wadkin 10ags and I’m interested to know about the 240v motor I have. I assume it is original to the machine.

The thing I don’t understand is this:
I thought watts equals amps x volts so 11.5 x 240 equals 2760w or about 2.7kw.
How many HP is this? The plate says 2hp - is that correct? I thought a 2.7kw motor would have a higher horsepower?
Any help/advice greatly appreciated.
Nick

 

[baldkev]

Im not an expert... but i think the amps is an indication of max draw on startup.
I would imagine if they put 2hp on the plate, it must be that.

 

[dephill]

Thats what I thought about the plate, I agree it must be right, although I wondered if there’s a smudge next to the ’2’ like ‘2.5’ perhaps.
Also I used a clamp meter on it and it runs unloaded at ~7.5A and ~50A momentarily on startup.
(Mounted in saw, with blade)

 

[Duncan A]

The formula W = VI only applies for dc electrics.
A power factor needs to be applied for ac, typically around 0.75 so this motor is rated at 11.5 x 230 x 0.75 = around 2kW.
By the way, 11.5A is the full load current, not the starting current, which could be around 70 - 90A, and not necessarily the current drawn if the motor is not working hard.
Furthermore the current drawn is used to calculate the input power (commonly referred to as P1) and the output power (P2) will be a fair bit less due to inefficiencies in the motor and whatever it is attached to.
I suspect that the 2hp (1.5kW) on the plate refers to output power.
Duncan

 

[dephill]

Cheers Duncan for the explanation. That clears it up nicely, I thought it might be to do with power factors but it all started going a bit over my head.
Cheers Kev too!
Nick