I have a 40hp DC motor and drive that I really need to reverse
rotation on. Part of the problem is the spindle control has one side
of the system burnt out, has been for years. When we moved I mounted
the motor differently and because of that it rotates the opposite
direction that it used to. Now I have the tooling unscrewing itself
and other chip problems so want to reverse it back to what we were
running. The machine used to run in either direction with M3/M4
commands but the system shorts itself out now in M3 and nearly blows
the control relay off the panel.
Could it be as simple as switching the 2 motor leads?
JohnF

"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.

Leo Lichtman wrote:
"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.


Yeah, that sounds like the best plan. A 40 Hp motor is going to have
commutating poles, and how you set up commutating poles on a reversible
motor gets complicated. Normally, I'd expect something like this to
just have a pair of big contactors to handle the reversing. Was this
a 4-quadrant servo drive? That's about the only reason I could think
of electronic reversing of a motor this size.

Jon

I have no clue what a 4 quadrant drive is. It's an old Reliance 480v 3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?







On Thu, 15 Sep 2005 19:51:50 -0500, Jon Elson
wrote:

Leo Lichtman wrote:
"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.


Yeah, that sounds like the best plan. A 40 Hp motor is going to have
commutating poles, and how you set up commutating poles on a reversible
motor gets complicated. Normally, I'd expect something like this to
just have a pair of big contactors to handle the reversing. Was this
a 4-quadrant servo drive? That's about the only reason I could think
of electronic reversing of a motor this size.

Jon

On Mon, 19 Sep 2005 19:56:56 GMT, JohnF
wrote:

I have no clue what a 4 quadrant drive is. It's an old Reliance 480v 3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?



Yes, it most certainly could. All it needs to do is reverse the
RELATIONSHIP of the feild and armature.




On Thu, 15 Sep 2005 19:51:50 -0500, Jon Elson
wrote:

Leo Lichtman wrote:
"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.


Yeah, that sounds like the best plan. A 40 Hp motor is going to have
commutating poles, and how you set up commutating poles on a reversible
motor gets complicated. Normally, I'd expect something like this to
just have a pair of big contactors to handle the reversing. Was this
a 4-quadrant servo drive? That's about the only reason I could think
of electronic reversing of a motor this size.

Jon

On Mon, 19 Sep 2005 19:56:56 GMT, JohnF
wrote:

I have no clue what a 4 quadrant drive is. It's an old Reliance 480v 3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?







On Thu, 15 Sep 2005 19:51:50 -0500, Jon Elson
wrote:

Leo Lichtman wrote:
"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.


Yeah, that sounds like the best plan. A 40 Hp motor is going to have
commutating poles, and how you set up commutating poles on a reversible
motor gets complicated. Normally, I'd expect something like this to
just have a pair of big contactors to handle the reversing. Was this
a 4-quadrant servo drive? That's about the only reason I could think
of electronic reversing of a motor this size.

Jon

In order to reverse the rotation of the drive the armature leads as
well as the field leads need to be reversed, also the tach leads.

Direction of the motor is determined by the polarity of the armature,
the large contactor is just the the loop contactor and only comes up
when the drive is enabled.

One thing you may try is just reversing the speed command the +-10vdc
velocity signal from the cnc.

The manual for the drive is very clear about how the spindle rotation
direction is determined.

You have to be very careful as the motor will run away and cause you
heart attack.

Regards


Daveb

On Mon, 19 Sep 2005 19:56:56 GMT, JohnF
wrote:

I have no clue what a 4 quadrant drive is. It's an old Reliance 480v 3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?







On Thu, 15 Sep 2005 19:51:50 -0500, Jon Elson
wrote:

Leo Lichtman wrote:
"JohnF" wrote: (clip) Could it be as simple as switching the 2 motor leads?
^^^^^^^^^^^^^^^^^
On a motor with permanent magnets for the field, it would be, but a motor
that large is going to have a wound rotor and a set of field windings.
Reverse either, but not both. If you reverse the connections to the
brushes, that should do it.


Yeah, that sounds like the best plan. A 40 Hp motor is going to have
commutating poles, and how you set up commutating poles on a reversible
motor gets complicated. Normally, I'd expect something like this to
just have a pair of big contactors to handle the reversing. Was this
a 4-quadrant servo drive? That's about the only reason I could think
of electronic reversing of a motor this size.

Jon


Was just looking at the manual, you may want to swap just the armature
A1 & A2 however you must also swap the tach leads.

This should do it, how you like AZ ??

Best


Daveb

According to DaveB:
On Mon, 19 Sep 2005 19:56:56 GMT, JohnF
wrote:

I have no clue what a 4 quadrant drive is.

One where the electronics can supply current to the motor of
either polarity with voltage of either polarity. (An example of one of
the stranger ones would be when the load is driving the motor faster
than you want, so it is generating voltage to keep the voltage positive,
while the controller (drive) is providing current in the opposite
direction, to try to bring the speed down to what is desired.

The first quadrant is positive voltage and positive current.
Quadrent 2 is (I think) positive voltage and negative current. Quadrant
3 is negative voltage and negative current (motor being run in reverse),
and quadrant 4 is negative voltage and positive current. (I may have
the order of these wrong, but the drive is at least capable of operating
in all four of those conditions.)

It's an old Reliance 480v 3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?

Or -- could it be powered from a center tapped full wave bridge,
or a H-bridge of drive transistors to be capable of reversing the
voltage to either winding? No need to switch diodes then, just let the
amplifier driving the output know what you want it to do.

An H-bridge, in case you are wondering, is as follows (as usual,
please use a fixed pitch font to view this to avoid distortion adding to
the confusion):


(+)-----+-------------------+
| |
(a)-K (b)-K
| + |
+-------/(M)/-------+
| - |
(c)-K (d)-K
| |
(-)-----+-------------------+


The 'K's are transistors.

The 'M' is the motor (with brushes)

(a), (b), (c), and (d) are control voltages into their transistors.

(+) and (-) are the DC inputs from the power supply.

To run the motor forward, turn on transistors (a) and (d), so
(a) pulls the '+' side of the motor high, and (d) pulls the '-' side of
the motor down, so it is operating normally.

To run the motor in reverse, turn on transistors (c) and (b).
(c) pulls the '+' side of the motor down to negative voltage, and (b)
pulls the '-' side of the motor high to positive voltage, so it has
reverse voltage applied to it and thus is rotating backwards (or at
least is trying to).

The motor should have a means of determining what the motor
speed is (in a servo system, there is a tach generator on the motor
shaft), so you adjust how hard the transistors are turned on to adjust
the drive to it. In the case of a permanent magnet field motor, you
also want to measure the current into the motor, and make sure that it
does not exceed a specified value -- because too much current can
demagnetize the pole pieces in the motor.

If you don't have a tach generator for speed feedback, you can
turn off the drive to all four transistors for a moment every so often,
and see what voltage is being generated by the motor. (Easy enough to
do with a switching regulated drive -- more difficult if you are using
standard analog drive -- and a lot more energy wasted as heat in the
transistors, too.

The "nasty contactor" in your drive may be to switch in a load
resistor if the motor is being driven by the load and doesn't want to
slow down. The electricity generated by the motor is switched into the
resistor to load it down.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"JohnF" wrote in message
...
I have no clue what a 4 quadrant drive is. It's an old Reliance 480v
3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?


As far as I know, Reliance drives starting from the mid 70's use SCR's
connected to the 3 phase lines (as do GE drives) for armature voltage.
There is a separate module for field excitation.

Is this a MaxPak series drive?

On Tue, 20 Sep 2005 04:55:58 GMT, "Rick" wrote:


"JohnF" wrote in message
.. .
I have no clue what a 4 quadrant drive is. It's an old Reliance 480v
3
phase drive with a large bank of rectfiers and a rather nasty
contactor (1). I don't understand exactly how it reverses itself
unless it switches a bank of diodes to change the +/- of the motor
input or could it do it by changing the +/- of the field windings?


As far as I know, Reliance drives starting from the mid 70's use SCR's
connected to the 3 phase lines (as do GE drives) for armature voltage.
There is a separate module for field excitation.

Is this a MaxPak series drive?

Hello Rick I think the drive was a VSR drive (nick) the power unit is
S3R is the design number.

I built the machine originally many year's ago and have the
documentation for that drive.

I bought that drive new in the box (was sitting in bone yard) about 20
years ago and used it in that machine.

Says a lot for that drive it has a lot of hours on it by now and the
only failure I'm aware of was the field regulator card went out last
year.

This motor drives a spindle via silent chain and when running is
something to stand back from.........lol.

Anyway, I think after John moved to the new location somehow the
roatation got backwards and should be easy to sort out.

Best Regards

Dave B



Daveb