Can I run a 230 motor at 250 volts

[broadgage]

It should be fine.
The nominal or declared voltage in the UK is 230 volts, and the maximum permitted is 253 volts (230 +10%)
Therefore the measured on load voltage of 250 volts is within the UK permitted tolerance.

If the motor is an induction motor, and was designed for 50 cycles, then at 60 cycles it will run faster, and develope more horsepower. This is unlikely to lead to overheating since the internal cooling fan will also run faster.

If the motor is a brush type, then the increased frequency is of almost no importance and the motor will be fine.

It might be prudent to re-check the on load voltage at different times of day, in case it rises above 253 volts at times of low load/increased voltage from your utility.

 

[winnie]

In an AC induction motor, the same coil carries a single current that performs both torque production and magnetic field production. Yet this composite current flow can be described in terms of its torque production and magnetic field production.

One additional point: if you ask why the 'torque producing current' doesn't produce a magnetic field, the answer is that it does...but this current flow is balanced by the current flow induced in the rotor, which is producing its own magnetic field. The _net_ magnetic field is what results from the 'magnetizing current' component of the supply current.

A similar effect is seen in transformers. When you increase the load on the transformer secondary, the current flowing in the primary increases. Clearly there is more current flowing in the wires. The secondary current acts to balance the increased primary current, and the total magnetic core flux actually goes down.

-Jon

 

[macmikeman]

I have a drill press at work that is labeled at 230 volts. I have a single phase 480 to 240
2kv transformer hooked up. Im getting about 260 volts on the secondaries when not running and about 250 volts when running but no load, am I looking at trouble?

Let me do this again: " 110.4 Voltages. Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equiment shall not be less than the nominal voltage of a circuit to which it is connected."

"Should be ok" and "is ok" are different. The motor will function with no problems per all the above responses except it is a code violation to run that motor on a circuit with a nominal 260 volt.

 

[jim dungar]

Let me do this again: " 110.4 Voltages. Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equiment shall not be less than the nominal voltage of a circuit to which it is connected.

The article 100 defines Voltage, Nominal. If we apply 110.14 using measured voltages, we would rarely be able to connect a standard US motor to a standard voltage system.

 

[jcormack]

Not really

Not really

The problem with high voltage is that the motor will have a lower current, and will therefore not be able to develop as much torque. I should think that torque is a critical parameter for a machine like a drill press.

Actually, when all things are considered the Torque available (starting, running, and max) are actually related to the SQUARE of the voltage applied. For example if you use a reduced voltage starter that reduces the initial voltage by 50% - the available starting torque is reduced to 25% of normal. Most Motor companies provide speed-torque curves for their motors at 100% voltage and 90% voltage (at the terminals). Here is a link to some equations. http://powerlearn.ece.vt.edu/modules/PE2/index.html

 

[DRGREG]

Educate this backwoods boy. What's a hob?

cf

I do believe it is what us yanks call a "cook top".

 

[Jraef]

This chart reflects the generally accepted relationships of applied voltage to design voltage in AC motors, and how torque, current and heat will be affected.

From this you can see that although initially the current drops when voltage is increased, at 10% above design voltage the current is goping to be significantly hiogher. This is because as the motor saturates, the power factor and efficiency drops, and because a motor is a "dumb animal", it pulls more current to try to keep doing the same work.

 

[Besoeker]

If the motor is an induction motor, and was designed for 50 cycles, then at 60 cycles it will run faster, and develope more horsepower.

Provided you increase the voltage too.

 

[btharmy]

If all this calculations and such are too confusing you could always just use the transformer, make sure the feeder to the motor is about 150-200ft. long (run it around the room a couple times) your resulting voltage drop should put you in the ballpark.

 

[scott657]

Thanks folks