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Old September 26th, 2003, 05:02 AM   #1
cciblazer
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120 volt speed control

Does anyone know where I can find any information on 120 volt speed controls for a motor? The motor is 1/2 hp.
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Old September 26th, 2003, 07:18 AM   #2
Pierre
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IF you are writing about dc control AND you mention that the source is 120 Vac THEN you have a look at KBIC-120 .

It will drive a dc motor with 0-90 dcV.
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Old September 26th, 2003, 12:09 PM   #3
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I cannot think of any conroller for single hase motor,
but if you must use 120VAC single phase power source,
you can use VFD drive and 3phase motor (208 or 240V).
There are several brands offering small VFDs running
happily from single phase line.
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Old September 26th, 2003, 05:07 PM   #4
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What you need to do is a search for VARIAC

A variac is a variable ac transformer, these were used alot "in the old days" for motor speed control, heater control, and lights. Technically they are still used alot, just differently.

This is a simple application using a variac with a light bulb

A variac is a very uniques device, it can be made to step up the voltage higher than incoming voltage, be variable over the full range, AND there are no harmonics added to the line voltage.

Note: there are limitations involved when using as motor speed control.
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Old September 27th, 2003, 12:58 AM   #5
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Need more info. on motor

What type on motor is it? Most 120 volt, 1/2 HP motors are capacitor start/induction run. Other common types are split phase and capacitor start/capacitor run. The speed of these motors cannot be varied. Any motor with a starting switch which opens near full speed and cuts out a start winding cannot be speed varied. Do not connect a Variac to this type of motor.

Variacs can be used with shaded-pole motors but it is doubtfull a 1/2 HP motor would be this type.

See the following link for details on different types of single phase motors.

http://www.iprocessmart.com/leeson/l...se_article.htm
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Old October 4th, 2003, 02:45 PM   #6
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Some 120 VAC Single Phase Motors Can Be Used With Speed Controllers

I have had applications where I could have used a speed controller on 120 VAC Single Phase motors. Usually we had installed mechanical means like a vari-pully. I had spoke to some friends about this and one of them said he had seen an electrical speed controller in a Grainger catalog. So the research for information began.

FROM THE GRAINGER CATALOG:
Grainger 120 Vac Single Phase Speed Control

Variable AC Speed Control, Output Voltage 120 VAC, Power Rating 1.5 HP, Enclosure NEMA 1, Input Voltage 120 VAC, Maximum Current 15.0 Amps, Length 5.53 Inches, Depth 3.80 Inches, Width 4.00 Inches, For Adjustable Speed PSC motors.

Grainger Item: 5JJ62
Price (ea) : $174.75
Manufacturer: DART CONTROLS
Mfg. Model#: 55AC15-21

Grainger Catalog 394 Page: 47

OK that looked applicable (a little cheaper than 3 phase VFD's). But the type of single phase motor is very important. So now began looking up types of 120 VAC single phase motors. Vic's link helped very much. Here is some of the information I found that may help others wanting to try this in their application.

UNIVERSAL MOTORS
A universal motor is one that operates on either single-phase ac or dc power. These motors are normally made in sizes ranging from 1/ 200 to 1/ 3 horsepower.

You can get them in larger sizes for special conditions. The fractional horsepower sizes are used on vacuum cleaners, sewing machines, food mixers, and power hand tools. The salient-pole type is the most popular type of universal motor. The salient-pole type consists of a stator with two concentrated field windings, a wound rotor, a commutator, and brushes. The stator and rotor windings in this motor are connected in series with the power source. There are two carbon brushes that remain on the commutator at all times. These two brushes are used to connect the rotor windings in series with the field windings and the power source . The Universal motor does not operate at a constant speed. The motor runs as fast as the load permits; i. e., low speed with a heavy load and high speed with a light load. Universal motors have the highest horsepower-to-weight ratio of all the types of electric motors.

The operation of a universal motor is much like a series dc motor. Since the field winding and armature are connected in series, both the field winding and armature winding are energized when voltage is applied to the motor. Both windings produce magnetic fields which react to each other and cause the armature to rotate. The reaction between magnetic fields is caused by either ac or dc power.

Permanent split capacitor
A permanent split capacitor (PSC) motor NOT the same as Split-Phase-Capacitor Start motors. Because the run capacitor must be designed for continuous use, it cannot provide the starting boost of a starting capacitor. Typical starting torques of PSC motors are low, from 30 to 150% of rated load, so these motors are not for hard-to-start applications. However, unlike split-phase motors, PSC motors have low starting currents, usually less than 200% of rated load current, making them excellent for applications with high cycle rates. PSC motors have several advantages. They need no starting mechanism and so can be reversed easily. Designs can be easily altered for use with speed controllers. Permanent split capacitor motors have a wide variety of applications depending on the design. These include fans, blowers with low starting torque needs, and intermittent cycling uses such as adjusting mechanisms, gate operators and garage door openers, many of which also need instant reversing.

Shaded-pole
The shaded-pole motor is a single-phase induction motor that uses its own method to produce starting torque. Instead of a separate winding like the split-phase and capacitor motors, the shaded-pole motor's start winding consists of a copper band across one tip of each stator pole . This copper band delays the magnetic field through that portion of the pole. When ac power is applied, the main pole reaches its polarity before the shaded portion of the pole. This action causes the shaded poles to be out of phase with the main poles and a weak rotating magnetic field is produced. Because of the low-starting torque, it isn't feasible to build motors of this type larger than 1/ 20 horsepower. They are used with small fans, timers, and various
light-load control devices. Remember, all single-phase induction motors have some auxiliary means to provide the motor with starting torque. The method used for this starting torque depends on the application of the motor.

Shaded-Pole motors have only one main winding and no start winding. Because the shaded pole motor lacks a start winding, starting switch or capacitor, it is electrically simple and inexpensive. Plus, speed can be controlled merely by varying voltage, or through a multi-tap winding.

I hope you find this helpful

Thanx Dan
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