High and low speed motor.

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kda3310

kda3310

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I have a 1.5hp, 2spd, 11a, 1ph, 110v at 60hz motor. (Hot tub motoer and pump) It has a high and low speed on the motor. On high speed I assume it is running at 60hz. Does it run less than 60hz on low and does it draw more amps with less hz?
 
kda3310 said:
I have a 1.5hp, 2spd, 11a, 1ph, 110v at 60hz motor. (Hot tub motoer and pump) It has a high and low speed on the motor. On high speed I assume it is running at 60hz. Does it run less than 60hz on low and does it draw more amps with less hz?
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The HZ doesn't change and it will draw less amps on low speed.
 
There is likely more than one set of windings with a common lead that is internally connected to one end of both sets.

Number of poles in the motor directly effects speed in both single phase and three phase induction motors.

Frequency also will effect speed in both single phase and three phase.
 
I have not worked with a VFD much but, we had a VF Dive that kept falting with an over current. The motor runs at two speeds. The dive is 3ph 480v but the voltage to the motor from the dive is not 480v. Does it control seed with volts or hz?
 
kda3310 said:
I have not worked with a VFD much but, we had a VF Dive that kept falting with an over current. The motor runs at two speeds. The dive is 3ph 480v but the voltage to the motor from the dive is not 480v. Does it control seed with volts or hz?
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A variable frequency drive varies both voltage and frequency. Usually, the voltage and frequency stay in the same ratio so, for example, at half nominal frequency, you would get half nominal voltage.
 
I believe the typical two-speed motor reduces speed by simply powering less windings, not fewer poles, thus reducing torque.

In other words, it's not a synchronous motor.
 
Maybe I do not understand what y'all are calling poles. I have taken apart a motor before seen the windings. Are y'all referring to the number of phases when talking about poles or something else?
 
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LarryFine said:
I believe the typical two-speed motor reduces speed by simply powering less windings, not fewer poles, thus reducing torque.

In other words, it's not a synchronous motor.
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I suppose that is a possibility, but still think there is multiple windings and you are simply energizing different ones by energizing different leads. Your idea may work on shaded pole or PSC motors but not likely on other induction motors. I don't see the standard squirrel cage motor as a synchronus motor. Synchronus speed of a 2 pole 60 HZ motor is 3600 RPM. I dare you to find one that does not run slower than that at rated load and frequency unless is truly is a synchronus motor.

kda3310 said:
Maybe I do not understand what y'all are calling poles. I have taken apart a motor before seen the windings. Are y'all referring to the number of phases when talking about poles or something else?
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Number of magnetic poles in the stator windings in the motor. Has nothing to do with number of phases, voltage, or number of turns in the windings. A 2 pole motor has the magnetic poles 180 degrees apart. A 4 pole has them 90 degrees apart. A 6 pole has them 60 degrees apart. These are the most common motors found.

Typical speeds are 2 pole - 3450 RPM, 4 pole - 1725 RPM, 6 pole 1100 RPM.

Synchronus speeds (the speed of the magnetic fields, and the speed of the rotor if there would be no ineffeciencies) are 2 pole - 3600, 4 pole 1800, 6 pole 1200.
 
"Poles are the number of sets of three-way electromagnetic windings that a motor has.

In the simplest three-phase motor, there are 3 separate electromagnets formed by the single set of three-way windings. Thus, there is a set of North-South electromagnetic poles formed. This motor is said to have "2 poles" (although strictly speaking, the motor has 6 electromagnetic poles)."

That's about as clear as mud.

Here's another motor.
http://www.google.com/imgres?imgurl...gQfg_8HDAQ&page=1&ndsp=50&ved=1t:429,r:12,s:0

For sure, this
http://en.wikipedia.org/wiki/Shaded-pole_motor
has two poles. Each are "shaded" with heavy wire to give, IIRC, a starting torque and to determine the direction of rotation.
 
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So, there is 3 windings on the case and 3 windings on the stator and only two alternating negative and positive poles propelling it forward? If I understand this right.
 
kda3310 said:
So, there is 3 windings on the case and 3 windings on the stator and only two alternating negative and positive poles propelling it forward? If I understand this right.
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You are on the right track. Don't know what you are referring to when you say case vs stator. There are stator windings and there are rotor windings. The stator is the stationary windings located just under the outer case of the motor, it includes all windings in this area all the way around.

All motors have a rotor winding but this winding is the type that will vary from one type of motor to the next. This is the winding is attached to the rotating shaft in some way and moves in unison with the rotation of the shaft. In a squirrel cage induction motor these windings are simply metal bars (usually copper I think) with a shorting ring attached at each end to form a 'squirrel cage'. I think it gets that name because it looks like the exercise wheel found in pet rodent enclosures.

The induction motor gets its name because the current in the rotor windings is induced by magnetic fields from the stator. There is current flowing through these bars and shorting rings causing additional magnetic fields used to create more repelling between stator magnetic fields that cause the rotor to turn. Motors with wound rotors need to have slip rings or commutators and a contact device to transfer current to the rotor.

back to what you said with 3 windings-
In a 3 phase 2 pole motor there will be three windings - one per phase in the stator making one pole, and 3 other windings - one per phase placed 180 degrees around the stator from the first 3 making the second pole.

In a single phase motor there will be the main and aux/start windings making one pole with the same located 180 degrees apart making the second pole.
 
kwired said:
You are on the right track. Don't know what you are referring to when you say case vs stator. There are stator windings and there are rotor windings. The stator is the stationary windings located just under the outer case of the motor, it includes all windings in this area all the way around.
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Ok, so there is six windings on the stator. Now I see how the poles are 180 degrees apart. But, the windings on the rotor are only there to repel against the two poles then?
 
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