Motor starter

[MAXIWANG]

Can anybody tell me the difference between manul starter, magnetic starter and combination starter? How to choose which one i should use? thanks in advance.

 

[itsmoked]

As I understand it (or miss-understand it)

Manual Starter: Large lever you throw. Mechanically connected to the contacts that close. (Think 'safe' knife switch')

Magnetic starter: Usually called a "mag-starter". A big contactor (relay) in a box that gets closed buy a control unit or a button.

Combination Starter: A 'mag-starter' in a box with overload protection added/integrated.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Laplacian]

The combination starter is a "mag-starter" with short circuit protection added/intergrated. Overload protection would be part of the contactor assembly.

 

[itsmoked]

Ah, roger that! Thanks Laplacian.

So correction MAXIWANG;

Mag Starter has a contactor(large relay) and overload protection.

The Combination Starter is a Mag Starter with [green]short circuit protection[/green] included in the enclosure.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hey guys, don't forget the manual disconnection of all ungrounded contacters that is a critical feature of the combination starter and is similar to the large lever mentioined above.
yours

 

[dpc]

I'll just add that a "starter" per NEMA terminology always includes motor overload protection of some type.

A manual motor starter for a small fractional hp motor may resemble a simple light switch on the outside, but will have some type of thermal protection built-in. If it doesn't have overload protection, it's a switch or disconnect.

NEMA rated starters also have a horsepower rating.

If you need to automatically (or remotely) control the motor, you need a magnetic contactor.

contactor + overload protection = starter

 

[itsmoked]

Good point waross.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rbulsara]

Well let me try too:

In the USA:

Starter, manual or automatic, by definition includes overload protection built- in.

Manual starter: Is exxactly what it says, which requires a manual action that result in closing of the main (motor power) contacts directly without need for a control circuit. This includes a simple spap switch typde device but with a thermal overload built in. A ordinalry switch can also be used as manual starter, as long as, there is motor overload protection built in some where, typically in the motor itself (example: the kitchen sink garbage disposal.

Magatic starter: Includes a contactor that is contorlled by energizing or deenergizing its coil, either automatically or manually. The key here is ther presence of a control circuit. Since the coil/plunger is a magnetic device it is called a magnetic starter.

Combination Starter: A "combination" of a stater, such as magnetic, "and" a disconnect device. This disconnect can be a switch or a breaker or modlded case switch.

A starter disconncet is required by Code (NEC), so if you use just a starter, a separate disconncet ahead of the starter is still required.

What you use when, it depends on the application. Get out in the filed and review some installations and you will know.

 

[MAXIWANG]

Thanks a lot for all the response.

 

[MAXIWANG]

I looked into my case. Now I have a 1/4HP Fan Powered Box which will be controlled by the motion sensor inside the boardroom. In this case, can I still use manual starter? or I have to use magnetic starter since the motor will be turned on and off automatically by the motion sensor? thanks for everybody.

 

[Laplacian]

You will need the magnetic starter as this is what applies the mechanical (by use of electromagnetism) force required to close the contacts on the contactor.

Ensure your motion sensor has an output contact rated for the inductive load of the starter coil or use an interposing relay rated for such purpose. If you post more information about your sensor it would be helpful.

 

[nightfox1925]

You may use a combination starter in the form of a disconnect switch (or MCP)+contactor+overload combination with associated control circuit will suffice assuming your local starter is connected to a feeder circuit breaker. The starter should be UL listed and tested as a combination per NEMA standards. If you are using any of these combination, rating tables published by different manufacturers are available for your reference like cutler-hammer or square D (NEMA rated starters).

In addition, the starter control circuit should have RED/GREEN/AMBER indication lamps, Hand-Off-Auto selector switch and an interposing relay. The H-O-A switch will enable you to override the sensor control and do local testing as you require and the interposing relay will isolate your instrument (sensor)circuit from your electrical circuit. The sensor controlled interposing relay will be wired at the Auto position. if installed outdoors, ensure that the ambient temperature is specified in your starter specification. If your starter is located indoors and the motor is installed outdoors (different temperatures), select an ambient-compensated overload relay.

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[waross]

For 1/4 Horsepower, buy a manual starter. It will be a little bigger than a light switch but it will fit in the same space. Find a relay with contacts rated about 20 amps and put that after the starter to control the motor. Use you sensor to control the relay.
yours

 

[nightfox1925]

Thanks waross...For a 1/4 HP motor, I really got so jumpy on my specifications!

GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[waross]

Hi 02101972
I know the feeling. Sometimes we visualize a machine as a few kilowatts and it turns out, after more information is supplied, to be a few megawatts. Here we were all expecting something much larger.
respectfully

 

[jraef]

Actually, you never stated whether the motor is 1 phase or 3 phase, it makes a difference.

If 3 phase, the "relay" is unlikely to have any HP rating and a 3 phase manual motor starter plus a 3 pole relay is going to cost a lot more than a 3 phase mag starter anyway.

If single phase, then waross is right, just make sure the relay has an actual HP rating on the label. Some cheap ones do not (learned from experience unfortunately) and cannot be used to switch inductive loads such as motors.

Also, with either method you will need some form of Short Circuit Protective Device and possibly a lockout means depending on your installation and local codes. You may be able to get away with the circuit breaker feeding your conductors as the SCPD, but lockout requirements may mean also having a padlock tab on the manual motor starter or another disconnect switch within sight of the motor.

If in doubt, hire an electrician.

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