Phase Control Thyristors

What is Phase Control Thyristor?

A thyristor, also known as silicon controlled rectifier (SCR) is a solid-state unidirectional semiconductor device made of silicon. Basically, a thyristor or SCR is a four-layer silicon semiconductor structure of p-n-p-n type.

In fact, SCR (Silicon Controlled Rectifier) is a trade name given to the thyristor by General Electric Company.

The thyristor acts as a switch (or a latch), conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed or the voltage is removed. In a three-terminal thyristor, a small current at its Gate lead controls the larger current of the Anode to Cathode path.

Phase Control Thyristors are typically used in electric equipment using phase control, to change the output voltage or switch the current supply on or off, operating at low frequencies (most often near AC mains frequency).

Thyristors have very low losses in the conducting state, which makes them attractive devices for efficiently controlling very high currents and energies.

All disk-type thyristors presented on this site have a standard press-pack type ceramic housing. They are pressed with a relatively high force into heat-sinks which also serve as electrical contacts to the thyristor terminals.

The forward current rating I_TAV ranges from 100A to 15000A, and the range of reverse blocking voltage V_RRM is from 100V to 9000V.

For phase control thyristors, in contrast to fast thyristors or fast switching thyristors, the turn-on time and turn-off time are not standardized.

Today, Phase Control Thyristors (PCT) are a key component in high-power rectifiers, soft starter, power supplies, phase-controlled rectification, high-power inversion, AC and DC motor control, AC/DC switching, power quality systems, among others. It is the number one choice in high power applications where the highest performance, reliability, and low conduction losses are required.

See also articles: Fast Thyristors, Fast Switching Thyristors, Thyristor Modules – Series Overview.

Phase Control Thyristors Westcode

Phase Control Thyristors KP series Jythyristor Factory are general purpose power disc thyristors.
Thyristors KP series are available with current ratings from 300A to 6800A and blocking voltages from 600V to 6500V.

Type	VDRM VRRM	IT(AV)M (TC=55°C)	ITSM	I2t	VT0	rT	Tvj max	RthJK	Case	Dimensions ØDxØdxH	Data sheet
	V	A	A	A2·s	V	mΩ	ºC	K/W		mm	PDF
N0465WN160	1600	465	4500	101×1000	0.900	0.850	125	0.0800	w90	42x19x14
N0465WN140	1400	465	4500	101×1000	0.900	0.850	125	0.0800	w90	42x19x14
N6012ZD020	200	6012	65000	21.13×106	0.853	0.029	140	0.0110	w64	110x73x26
N6012ZD040	400	6012	65000	21.13×106	0.853	0.029	140	0.0110	w64	110x73x26
N2154JK020
N1547NC160
N0616LC400

Fast Switching Thyristors Westcode

Type	VDRM VRRM	IT(AV)M (TC=55°C)	ITSM	I2t	tq	VT0	rT	Tvj max	RthJK	Case	Dimensions ØDxØdxH	Data sheet
	V	A	A	A2·s	µs	V	mΩ	ºC	K/W		mm	PDF
P0295WC12E	1200	295	2700	365000	25	1.600	1.230	125	0.0950	w8	42x19x14
P0295WC12D	1200	295	2700	365000	20	1.600	1.230	125	0.0950	w8	42x19x14
P0848YC04C	400	848	8750	383000	15	1.010	0.305	125	0.0500	w58	42x25x14
P0848YC04B	400	848	8750	383000	12	1.010	0.305	125	0.0500	w58	42x25x14
P0838LC06C	1110	600	12300	750000	15	1.200	0.280	125	0.0320	w10	58*34*27
P0838LC06B	1110	600	12300	750000	12	1.200	0.280	125	0.0320	w10	58*34*27

Medium Voltage Thyristors Westcode

Air-cooled and Water-cooled heat-sinks for disc type thyristors

The operation of semiconductor devices at high currents and high reverse voltages is accompanied by high power in the p-n junction of the silicon chip.

Air and water heat sinks are used for cooling power SCR thyristors.

The heat sink is characterized by the value of power dissipation and the area of the cooling surface and is selected on the basis of the required heat dissipation at the operating power of the thyristor.

In disk-type thyristors, the necessary compression of the press contacts is provided only if they are assembled with heatsinks.

To keep electrical losses to a minimum and heat dissipation to a maximum, the necessary clamping force Fm must be provided during assembly.

Range of values of axial force on thyristor Fm, i.e. thyristor compression force, is from 10 to 100 kN depending on package diameter (housing type) and is specified in datasheet.

Heatsinks are used for disc (tablet type) semiconductors with сontact surface diameter from Ø19 mm to Ø100 mm.

See for more information about heatsinks for disc type SCR thyristors:
"Air-cooled heatsinks O series", "Air heatsink SF series", "Water heatsink SS series".

Installation recommendations for power disc type thyristors

The reliability of heat transfer and electrical contact between the mating surfaces of the thyristor and the cooler over the entire temperature range is ensured by appropriate torque (clamping force).

Before assembly you should perform visual inspection (1) contact surfaces for mechanical damages and wipe (2), soaked with alcohol (toluene, gasoline, acetone).

After inspection, fix the current contacts (leads), install a pin to fix the alignment of the structure.

To improve the parameters of heat transfer it is recommended to lubricate (3) a thin layer of silicone thermal conductive paste before the assembly, which is not a mandatory condition for installation.

Install the thyristor (3), the second part of the cooler, the fiberglass insulator and the thrust washer.

To thread the traverse (4) and evenly tighten the nuts. Make sure no misalignment and evenness of the contact surfaces.

When the parts are sufficiently clamped but moveable, we recommend placing the cooler on a flat surface and checking the tolerance for parallelism of the overall adjacent plane of the surfaces (5).

Clamp each nut in turn (about a quarter turn) to the stop (6). The amount of deflection of the traverse determines whether the achieved clamping force corresponds to the required one.

After installation, the fasteners (nuts and washers) must be additionally secured against corrosion.

Tips and recommendations for power thyristors:

The power thyristors should not be operated for long periods of time at their limit load for all parameters. In this case, the safety factor is determined by the required degree of reliability of the device.

Replace a failed power thyristor with a thyristor that matches the parameters of the one being replaced.

Supercooling must be provided when operating in an environment with an elevated ambient temperature.

Periodic cleaning of power thyristors and coolers to remove dust and contaminants is recommended to ensure proper heat dissipation.

Inductive current dividers (often twisted toroidal wire) should be used to equalize currents between power thyristors connected in parallel. The most popular connection methods are closed circuit, common coil circuit, or power thyristor. The efficiency of current dividers in this case is determined by the cross section of the magnetic wire.

Prevention of voltage unbalance when power thyristors are connected in series is achieved by using shunt resistors connected in parallel with each thyristor. Voltage equalization in transient conditions is provided by connecting capacitors in parallel to each thyristor.

It is strictly forbidden to touch power thyristors under high voltage during operation.