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| P-GPS... |
 Posted: Mon Aug 24, 2009 5:34 am |
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Guest
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Hi,
I am trying to find an electrical hoist, which has variable speed,
single phase motors. I am unable to find any. Is there a technical
reason why? Or would it be a business reason? Any insight?
Thanks. |
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| dlzc... |
| Posted: Mon Aug 24, 2009 9:57 am |
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Guest
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Dear P-GPS:
On Aug 24, 8:34 am, P-GPS <premg... at (no spam) gmail.com> wrote:
[quote:121d48cb68]Hi,
I am trying to find an electrical hoist, which has
variable speed, single phase motors. I am unable
to find any. Is there a technical reason why?
[/quote:121d48cb68]
Single phase motors are fractional to small integer horsepower. You
will need VFD-rated motor windings, and make sure that you do not
overspeed the winding mechanism (so don't run the mechanism over 60
Hz, for example).
[quote:121d48cb68]Or would it be a business reason? Any insight?
[/quote:121d48cb68]
Small market, you are going damned slow anyway so why worry about
slower, the single phase inverter is at least 2x more expensive than
the three-phase version for the same motor power, control logic for
reversing the motor is orders of magnitude more complex, stuff like
that.
I suggest you find a vendor that offers hoists with less than 5 hp
drive motors, and single phase power is probably an expensive option.
David A. Smith |
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| P-GPS... |
| Posted: Wed Aug 26, 2009 5:38 am |
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Guest
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Hi,
I did not get you in some of your statements
[quote:43b9336913]Single phase motors are fractional to small integer horsepower.
What does this mean?[/quote:43b9336913]
[quote:43b9336913]You will need VFD-rated motor windings, and make sure that you do not
overspeed the winding mechanism (so don't run the mechanism over 60
Hz, for example).
[/quote:43b9336913]
Doesn't a speed controller limit the frequency to 60Hz, when connected
to a 60Hz main?
Even if the cost of a single phase motor is 2x that of a 3-phase
motor, we would like to get it. Are there any vendors who sell single
phase variable motors?
Thanks.
On Aug 24, 3:57 pm, dlzc <dl... at (no spam) cox.net> wrote:
[quote:43b9336913]Dear P-GPS:
On Aug 24, 8:34 am, P-GPS <premg... at (no spam) gmail.com> wrote:
Hi,
I am trying to find an electrical hoist, which has
variable speed, single phase motors. I am unable
to find any. Is there a technical reason why?
Single phase motors are fractional to small integer horsepower. You
will need VFD-rated motor windings, and make sure that you do not
overspeed the winding mechanism (so don't run the mechanism over 60
Hz, for example).
Or would it be a business reason? Any insight?
Small market, you are going damned slow anyway so why worry about
slower, the single phase inverter is at least 2x more expensive than
the three-phase version for the same motor power, control logic for
reversing the motor is orders of magnitude more complex, stuff like
that.
I suggest you find a vendor that offers hoists with less than 5 hp
drive motors, and single phase power is probably an expensive option.
David A. Smith[/quote:43b9336913] |
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| N:dlzc D:aol T:com (dlzc)... |
| Posted: Wed Aug 26, 2009 8:03 pm |
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Guest
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Dear P-GPS:
"P-GPS" <premgrps at (no spam) gmail.com> wrote in message
news:3fe7ee33-4e9a-4240-8c87-08e6aba2a201 at (no spam) 18g2000yqa.googlegroups.com...
[quote:5c43a8fc31]I did not get you in some of your statements
Single phase motors are fractional to small integer
horsepower.
What does this mean?
[/quote:5c43a8fc31]
They are small motors. < 5hp.
[quote:5c43a8fc31]You will need VFD-rated motor windings, and make
sure that you do not overspeed the winding mechanism
(so don't run the mechanism over 60 Hz, for example).
Doesn't a speed controller limit the frequency to 60Hz,
when connected to a 60Hz main?
[/quote:5c43a8fc31]
No. You can obtain VFDs that will overspeed by 20% or more, with
modifications they even run ozone generators at thousands of
hertz.
[quote:5c43a8fc31]Even if the cost of a single phase motor is 2x that of
a 3-phase motor, we would like to get it.
[/quote:5c43a8fc31]
For < 5hp, or over 4000 volts, you can get them. If you wanted
to pay 100x, you could get someone to make you one.
[quote:5c43a8fc31]Are there any vendors who sell single phase variable
motors?
[/quote:5c43a8fc31]
The motors are not variable, the drive is. And switching it from
"raise" to "lower" is much more complex than with a three phase
motor, and requires a whole 'nother control system.
David A. Smith |
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