2 Hp 120v Only?

[Metal]

It looks like everything above is correct

at 120volts 2 horsepower is roughly 6 amps draw, so thats what you'll see (or a little more) when near the optimal powerband for that device (which is where it should be geared for anyway)

30amps is likely the stall of the motor, if the motor gets anywhere near that its likely that the drum switch or something will melt down before the motor will.

you'll likely see more than the 15a rated going through that switch for a fraction of a second on startup (enough to trip a breaker) but not enough to melt something down, that said its a little bit hokey to under rate electrical components and hope the user doesn't push the device too hard.

 

[sk1nner]

I'm not sure I understand you. I currently have it plugged into a 20 amp circuit. Sometimes it will start and run fine. But sometimes it trips the breaker on start up. When it does that I can usually get it running by (I know this isn't best) leaving the switch on and flipping the breaker back on. I want to get away from this for safty and ease of use. With the motor rated at 29.7 amps I know I should go higher than a 30 amp (80% rule), but from what I've seen (I'm no electrition) it seems to only draw that current on startup. I've pushed it fairly hard when it's running and not had the breaker trip.

 

[BGHansen]

I've gone by the premise that 1 horsepower = 746 watts. Volts times Amps = watts. A 2 hp motor at 110V would draw under 14 amps.

Bruce

 

[Steve Shannon]

the switch is rated 15a@250v, it's sufficient for the motor.
i do find it odd to find a 115v motor @ 2 hp

I apologize, but it's important to me that I add to this.
The current rating and the voltage rating of a switch are not strictly inversely related. The current rating is based on the conductive elements of the switch and whether the switch is carrying AC current or DC current. There's always a safety factor, but generally speaking the maximum current rating of the closed switch doesn't care about the voltage.
The voltage rating describes how high of a voltage the switch can break and how much voltage the switch body is able to insulate against. The contact composition, speed of opening, size of the gap when opened, all play into the limit that can be interrupted.
Some switches rated at 15 amps for 250 vac may indeed be good for 30 amps at 125, but that cannot be assumed. When a switch is closed it's just a very low impedance resistor, so the maximum current rating is very important.

 

[Metal]

I'm not sure I understand you. I currently have it plugged into a 20 amp circuit. Sometimes it will start and run fine. But sometimes it trips the breaker on start up. When it does that I can usually get it running by (I know this isn't best) leaving the switch on and flipping the breaker back on. I want to get away from this for safty and ease of use. With the motor rated at 29.7 amps I know I should go higher than a 30 amp (80% rule), but from what I've seen (I'm no electrition) it seems to only draw that current on startup. I've pushed it fairly hard when it's running and not had the breaker trip.

The simpler way of remembering it, is amps = torque, right up until the motor can no longer turn (stall amperage) where most motors will smoke if kept there for too long, ideally you'd want the machine geared so that the motor stays in the ballpark of half way to stall torque which is where its total power output is at its maximum(its a curve)

You really dont have to worry about all that, you know if you are really punishing the machine and heat is going to become an issue, what ive done before on DC motors is solder capacitors across the leads on the motors, which helps calm down the amperage on motor startup by help, instead of starting up the motor 100% instantly with a contactor switch it starts it uses some sort of electronic trickery to slow that down to over a few fractions of a second, you'd have to do some research to figure out what size capacitors to use.

I've gone by the premise that 1 horsepower = 746 watts. Volts times Amps = watts. A 2 hp motor at 110V would draw under 14 amps.

Bruce

No you're 100% correct, for some reason my brain wasn't working this morning and I calculated it for 1hp not 2 and ended up a little over 6 amps

 

[mksj]

There is also an issue of the type of load being switched and it's characteristics. You often will see motor switches/contactors, etc. with different AC ratings, AC-1, AC-2, AC-3 through AC-23 and the same for DC-1 through DC-23. Usually XX-1 is non-inductive or slightly inductive through XX-23 which is switching large motors or high inductive loads which have very high inrush current such as large capacitor systems or transformers. There is also the voltage and Kw ratings of the switch. I have been burned several times on inexpensive Chinese rotary switches that where rated as AC-1 , but their AC-21 rating was a small fraction of the switches advertised rating and completely useless for switching motor systems. I actually would be concerned in this case that the switch is rated at only 15A at 250VAC, the rating would often be ~1/2 for a motor switch at 120VAC but this varies by switch design.
http://support.automationdirect.com/docs/iec_contactors.pdf
The Salzer switch has an AC21 rating at a full 32A, the 20A Chinese switch by comparison has an AC-4 of 1.5A, and is not even rated at an AC-21.

AC motors have power factors or efficiency, this particular motor is pretty low at 64%, which probably accounts for its much higher amperage rating, the 746W per Hp would be a perfect motor. I am in the process of replacing a 2Hp three phase motor, and was amazed that the stock motor's nameplate lists 6.6A at 220V the new one is 5.6A at 230V, both rated at 1.5kW.

 

[sk1nner]

So unless I'm really pushing my mill drill the only time I really use/need 30 amps is the short startup time. Makes sense

 

[Metal]

So unless I'm really pushing my mill drill the only time I really use/need 30 amps is the short startup time. Makes sense

Yep, figure this: at zero rpm the motor is not very efficient and also your switch only has two modes, off and 100% balls-to-the-wall on, its like slamming your car into drive with the pedal to the floor, except its sort of designed to do it, its likely the most stressful part of your work on the motor unless you are really punishing that drill