Why Use MG & 3PG Resistor Banks?
Speed Control Technology (SCT) designs and builds MG and 3PG Resistor Banks. The scope includes AC and DC Motor Control. Our MG and 3PG Resistor Banks have set the standard for reliability and quality for several decades. The grid material is Carpenter 316 stainless steel, with a temperature coefficient of just 5% between ambient and 400C (the nominal operating condition).
An MG Resistor Bank – tap points on alternate grids:

The Resistor Banks are resistant to rust, adjacent grids are argon welded together, to render them independent of rod pressure. A high impedance to earth is ensured by double insulation with epoxy glass tubes between tie rods and grids. There are heavy duty ceramic insulators at grid ends and at end plates. The bank assembly is built to ensure durable operation in tough steel production conditions. Ratings and dimensions conform to NEMA standards. Continuous and intermittent ratings are stated in the subsequent diagram.

MG Resistor Banks
An MG Resistor Bank conforms to the NEMA dimensions, with each grid on the bank identical, and a continuous connection along the assembly.
MG Resistor Bank

ORDERING INFORMATION | AMPERE RATING PER NEMA CLASS NUMBERS | |||||||
---|---|---|---|---|---|---|---|---|
BANK | OHMS | 90 | 170 | 160 | 150 | 140 | 130 | LIST NO. |
MG32 | 0.0465 | 350 | 440 | 513 | 575 | 680 | 792 | 40601 |
MG42 | 0.06 | 310 | 383 | 448 | 507 | 577 | 665 | 40602 |
MG52 | 0.075 | 280 | 319 | 410 | 456 | 537 | 598 | 40603 |
MG62 | 0.09 | 250 | 309 | 362 | 412 | 476 | 551 | 40604 |
MG3 | 0.156 | 185 | 232 | 270 | 303 | 358 | 417 | 40606 |
MG4 | 0.216 | 162 | 202 | 236 | 267 | 304 | 350 | 40607 |
MG5 | 0.25 | 147 | 184 | 216 | 240 | 283 | 315 | 40608 |
MG6 | 0.325 | 136 | 163 | 191 | 217 | 252 | 290 | 40609 |
MG8 | 0.544 | 109 | 137 | 159 | 178 | 205 | 238 | 40610 |
MG10 | 0.72 | 96 | 121 | 140 | 157 | 182 | 209 | 40611 |
MG12 | 0.9 | 85 | 107 | 123 | 136 | 160 | 182 | 40612 |
MG16 | 0.96 | 80 | 99 | 117 | 130 | 152 | 179 | 40613 |
MG20 | 1.52 | 66 | 83 | 96 | 108 | 128 | 149 | 40614 |
MG25 | 2.1 | 58 | 74 | 85 | 95 | 111 | 128 | 40615 |
MG31 | 2.85 | 51 | 65 | 75 | 83 | 98 | 110 | 40616 |
MG40 | 3.92 | 44 | 55 | 64 | 72 | 83 | 95 | 40617 |
MG50 | 7.6 | 34 | 42 | 49 | 54 | 64 | 74 | 40618 |
MG62 | 10 | 29 | 37 | 42 | 47 | 54 | 60 | 40619 |
Time On | Cont. | 15 | 15 | 15 | 15 | 10 | Seconds | |
Time OFF | Cont. | 15 | 30 | 45 | 75 | 70 | Seconds |
3PG Resistor Banks
A 3PG Resistor Bank conforms to NEMA dimensions, and all grids on the unit are identical but split into three separate phases:
3PG Resistor Bank

ORDERING INFORMATION | AMPERE RATING PER NEMA CLASS NUMBERS | |||||||
---|---|---|---|---|---|---|---|---|
BANK | OHMS | 90 | 170 | 160 | 150 | 140 | 130 | LIST NO. |
3PG3 | 0.044 | 185 | 232 | 270 | 303 | 358 | 417 | 40636 |
3PG4 | 0.056 | 162 | 202 | 236 | 267 | 304 | 350 | 40637 |
3PG5 | 0.070 | 147 | 184 | 216 | 240 | 283 | 315 | 40638 |
3PG6 | 0.088 | 136 | 163 | 191 | 217 | 252 | 290 | 40639 |
3PG8 | 0.144 | 109 | 137 | 159 | 178 | 205 | 238 | 40640 |
3PG10 | 0.20 | 96 | 121 | 140 | 157 | 182 | 209 | 40641 |
3PG12 | 0.25 | 85 | 107 | 123 | 136 | 160 | 182 | 40642 |
3PG16 | 0.26 | 80 | 99 | 117 | 130 | 152 | 179 | 40643 |
3PG20 | 0.40 | 66 | 83 | 96 | 108 | 128 | 149 | 40644 |
3PG25 | 0.50 | 58 | 74 | 85 | 95 | 111 | 128 | 40645 |
3PG31 | 0.75 | 51 | 65 | 75 | 83 | 98 | 110 | 40646 |
3PG40 | 1.12 | 44 | 55 | 64 | 72 | 83 | 95 | 40647 |
3PG50 | 2.0 | 34 | 42 | 49 | 54 | 64 | 74 | 40648 |
3PG62 | 2.25 | 29 | 37 | 42 | 47 | 54 | 60 | 40649 |
3PG80 | 2.56 | 26 | 32 | 36 | 41 | 46 | 53 | 40650 |
3PG150 | 4.64 | 17 | 18 | 21 | 24 | 27 | 31 | 40651 |
3PG200 | 5.92 | 10 | 12 | 14 | 16 | 18 | 20 | 40652 |
Time On | Cont | 15 | 15 | 15 | 15 | 10 | Seconds | |
Time OFF | Cont | 15 | 30 | 45 | 75 | 70 | Seconds |
Type 3PG Resistor Banks are ideal slip resistors for small to medium slip-ring motors, with closed-loop thyristor control, such as AC10. A NEMA 90 continuous thermal rating would be standard for this class of control, for which stability of resistance is the essential property.
Enclosed Resistors
Resistor Enclosures for MG banks is assembled from two and three-bank modules. These can be stacked in practical configurations to accommodate any number of resistor banks. High-temperature silicon-insulated cable is used for internal cabling. The standard enclosure colour is B26 Electric Orange.

Enclosure Dimensions
Enclosure Fig 1 | 1 bank + term chassis | H = 587 | W = 832 | D = 406 |
Enclosure Fig 2 | 2 banks + term chassis | H = 777 | W = 832 | D = 406 |
Enclosure Fig 3 | 3 banks + term chassis | H = 1020 | W = 832 | D = 406 |
Enclosure Fig 4 | 4 banks + term chassis | H = 1210 | W = 832 | D = 406 |
Enclosure Fig 5 | 5 banks + term chassis | H = 1400 | W = 832 | D = 406 |
Enclosure Fig 6 | 6 banks + term chassis | H = 1640 | W = 832 | D = 406 |
The enclosures can also be mounted side-by-side. They have knock-out holes for internal cabling.

Resistor Applications
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Rotor Resistors for Slip-ring Motors
01The principal need is to set an outer limit for the motor at each motor slip point.
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Discharge Resistors for Frequency Controllers
02The majority of frequency controllers have what is called a passive (un-controlled) front end. This means the controller can pass forward power only: it cannot return regenerated power to the mains system. The implication is that negative power (power developed by the load), must be dissipated within the control system.
-
DC Crane Resistors
03Conventional fixed voltage 230 and 440V dc technology places heavy emphasis on power resistors for starting and control. For hoist motions in particular; the inherent design necessitate bulk resistors to control the armature and field circuits; in particular during lowering.
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Neutral Earthing Resistors
04The term high resistance earthing pertains to the addition of a resistor into the neutral point of a distribution system; for the purpose of limiting earth fault currents to a controlled pre-determined level.