Power-Tronics VR758 User manual

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Power-Tronics, Inc.
Electronic Voltage Regulators and Static Exciters
P.O. Box 291509, Kerrville, Texas 78029
VR758 Voltage
Regulator
The VR758 is a cost effective, specifically
designed, single purpose voltage regulator
that will allow it to be used as either a flat
response or volts per hertz mode and is
compatible with most SCR loads such as
speed controls and UPS systems.
Specifications
Input Volts: 120 or 240acv
Frequency: 50 or 60hz
Voltage Regulation: +/- 1% of setting
Output Volts: 0-52vdc @ 120vac input
0-105vdc @ 240vac input
Maximum Continuous Output: 8adc
Minimum Field Resistance: 6.5Ω@ 120vac input
13Ω@ 240vac input
Min Residual Build up Volts: 5vac
Physical Size: 4.75 x 6 x 1 in.
Weight: 6 oz
Repairable: Yes
Internal Protection: No
External Voltage Adjustment: Yes
Flat Response Regulation: Yes, selectable
Volts Per Hertz Regulation: Yes, selectable
System Operating Indicator: Yes

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Caution: Read this Installation manual carefully. The
VR758 voltage regulator is not compatible with
options available for the UVR professional series
regulators. The VR758 is a specifically designed, single
purpose regulator and attempts to interface with UVR500
options will result in extensive damage to the regulator
and generator as well as possible personal injury.
The VR758 voltage regulator is specifically designed so that it
can be used in applications, which require either VPH, or Flat
Response regulation.
Before installation, you will need to know which mode that your application will require. The
charts below will illustrate how each mode operates.
Volts per Hertz
It is desirable to use the VPH mode in some
types of the applications listed below:
vGenerator is idled before and after use.
vPrime mover Hp is not enough for
starting large KW loads.
vUntrained or non-professional
operators.
vMisused equipment
Flat Response
Flat response is generally used in the following
applications:
vProfessional or well trained generator
operators.
vCritical applications such as Hospitals,
UPS systems and computer equipment.
vHard starting applications when the
prime mover HP is large enough for
large KW loads.
Generator Voltage
100%
50%
0%
Prime Mover 50% 100%
Speed
Generator Voltage
100%
50%
0%
Prime Mover 50% 100%
Speed

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Installation Instructions
Warning: Do not use digital equipment to read voltage, hz or amperage during this
installation. Use only Analog sensing equipment! Failure to do so may result in damage to of
equipment or in personal injury! Make sure that all setup is done off line. Always wear eye
protection and never hold the regulator in your hand when energized.
1. Install the regulator as shown in the drawing below:
1 2 3 4 5 6
FUSE
FUSE
A
B
C
N
GENERATOR
EXC FLD
OFF/ON
REMOTE
V
ADJUST
VR758
Wiring diagram for 208/240vac hookup. For 460/480vac hookup, connect to center taps of
main windings for 208/240vac input.
2. Determine if the application requires the regulator to be VPH or Flat Response mode.
The regulator is shipped as VPH.
3. If the regulator is to be configured as Flat Response, remove the jumper located on the
circuit card just below the internal voltage adjustment as shown below:
Remove this jumper for flat
response operation.
VR758
Use a fast acting 250vac
fuse. 10 amps or less!
If the external
adjustment is
not used, it is
not necessary to
jumper 5 and 6

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4. Turn the internal voltage control and stability control 15 or more turns counter
clockwise (left). This procedure is necessary in case the original factory settings have
been altered.
5. If you are using a remote voltage adjustment, set it at 50% of adjustment.
6. Start up the prime mover and bring up to operating speed and turn on the regulator
switch.
7. Set the internal voltage adjustment to the desired voltage setting for the generator
output. If the generator voltage is unsteady or flickering, adjust the stability adjustment
clockwise (right) until the voltage is steady and the green light is not pulsating. During
this adjustment, be sure to keep the generator voltage within 10vac of the original
setting with the internal voltage adjustment.
8. Place the generator on line and observe the frequency and voltage.
Application Troubleshooting
Problem: Possible Cause
No Voltage 1 3 5 7 9 11 13 15 20
Pulsating Voltage 4 5 6 12 16
Flickering Voltage 6 7 14 4
High Voltage 6 7 8 9 12 13 17 18 20
Voltage Drop on Load 5 8 10 12 16
Low Voltage 5 8 12 13
Poor Voltage Regulation 4 10 12 13 16
Voltage Changes With Engine Speed 2
No Voltage Control 13 19 20
Possible Cause:
1. Residual input voltage to the voltage regulator is below 3.5 vac.
2. Regulator is connected up for VPH operation.
3. Open exciter field or defective generator.

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4. Stability adjustment is not properly adjusted.
5. Open diode in exciter or shorted rotor in generator.
6. Loose component in voltage regulator.
7. Loose wiring connections.
8. Input voltage to regulator is too low.
9. Exciter field is grounded.
10. Stability adjustment is set too far clockwise.
11. Exciter fields are reversed.
12. Wrong selection of regulator wiring configuration.
13. Defective voltage regulator.
14. SCR or Inverter drive effecting generator wave form.
15. Regulator needs external flashing circuit.
16. Isolation transformer is too small.
17. Isolation transformer is needed.
18. Exciter fields are not isolated from other circuits.
19. Input and field circuit are being fed by a common cable or conduit.
20. Incorrect hookup or wiring.
For the latest product updates and technical
information, please visit our web site at:
www.power-tronics.com

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Bench Check Procedures for testing the VR758
Voltage Regulator.
1 2 3 4 5 6
120vac
fused at
5 amps
120v light
bulb, 25w or
higher
To test the regulator for flat
response regulation, remove the
selection jumper as shown in the
installation instructions.
1. Connect up the test unit as shown above.
2. Turn voltage and stability adjustments fully counter clockwise (left 25 turns).
3. Apply 120vac to the voltage regulator. The test light bulb should be off and the green
system indicator light should be on.
4. Turn the voltage adjustment clockwise until the test light turns fully on. The bulb will
only glow at1/2 brilliance with a 120vac input to the voltage regulator. Turn the voltage
adjustment counter clockwise until the light turns off.
5. Turn the stability adjustment clockwise until the test light turns on, then turn the
stability control counter clockwise until the test light turns off.
6. Momentarily short out the terminals 5 and 6. The test light bulb should glow. Remove
the short and the bulb should not glow.
7. Turn the voltage and stability adjustments fully counter clockwise (left 25 turns or
more) and remove the voltage from the regulator.
8. If the regulator performed all of the tests listed above, the regulator is good, if it failed
any of the tests, it is defective.
Test Light

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Installation form
It is very important that you fill out this form completely when installing a voltage regulator.
This form serves as a history record on the application. This form also contains the information
needed by Power-Tronics, Inc., for repair and troubleshooting of any product you may be
having problems with.
Product Other options
Serial Number
Date of Installation
Type of Generator Model #
Brush type [ ]
Brushless [ ]
AC Stator Information
Wired for Volts Phase Hz
Generator Configuration: Lead
Exciter/Rotor Information
Exciter field resistance Ω@ F+ / F- Ω
Exciter field volts vdc @ Slip Rings Ω
Description of problem with product or generator
Your phone number Name:
Your fax number Ship to Address:
Your email address Ship to City, State, Zip:

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PRODUCT WARRANTY
Power-Tronics, Inc., assumes no liability for damages due to incorrect voltage or other voltage
related damages resulting from either output of the generator or input to the generator exciter
system. These problems should be protected with external devices provided by the customer
such as fuses, surge suppressors, over/under voltage and frequency controls.
Power-Tronics, Inc., warranties only parts and workmanship of this product for a period of
1 year from the original date of purchase from Power-Tronics, Inc. Under warranty,
Power-Tronics, Inc. will replace, exchange or repair the defective product without labor or
parts cost to the customer. Remaining warranty of the original product will be transferred to
the replaced or repaired product. To obtain warranty, a copy of the original purchase receipt
must be sent in with the defective product, which clearly shows the purchase date and serial
number of the defective part. A repair request form must be sent in with the product before
repairs will begin. You can obtain this form through contacting Power-Tronics, Inc.. Send
repairs to: Power-Tronics, Inc., 2802 Cobbler Ln., Kerrville Texas USA 78028. Send in
repairs only by UPS or FedEx.
Any one of the following conditions will void the warranty:
vOverheating of the power supply resistor on the printed circuit card.
vOverheating of the SCR or freewheeling diode.
vPhysical damage to the printed circuit card, housing or components.
vUnauthorized repair or alteration of printed circuit card.
vConductive or corrosive contamination of the circuit card.
vRemoval of our company identification from the product.
vRemoval of any conformal coating of the printed circuit card or components.
vOverheating of foil on the printed circuit card.
vInappropriate or infeasible application
vUse on any external device other than manufactured by Power-Tronics, Inc.
No other warranty is expressed or implied.